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Q13. Examination of Body Fluids

Introduction

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Specimen Collection

• EDTA tube for cell count (prevents clotting)
• Plain/heparin tube for chemistry and cytology
• Sterile tube for microbiology
• Specimens should be processed within 1-2 hours; cytology specimens may need fixative

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Physical Examination

• Chylous effusion: milky, triglycerides >110 mg/dL
• Pseudochylous: cholesterol crystals, green tinge
• Hemorrhagic: RBC count >100,000/µL suggests trauma or malignancy
• Putrid odor: anaerobic infection

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Cell Count

• Performed using hemocytometer (Neubauer chamber) or automated hematology analyzer
• Diluting fluid: normal saline (for total count), Turk's fluid (for WBC count - lyses RBCs)
• WBC differential: cytocentrifuge (cytospin) preparation, stained with Wright-Giemsa

Interpretation of WBC count:

Differential cell count:

• Neutrophil predominance: bacterial infection, early inflammation
• Lymphocyte predominance: TB, malignancy, viral infection, chylous effusion
• Eosinophil predominance (>10%): air/blood in cavity, drug reaction, parasitic infection
• Mesothelial cells: normal lining cells; decreased in TB
• Malignant cells: mesothelioma, metastatic carcinoma

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Cytology

• Preparation: cytocentrifuge (cytospin) at 600-800 rpm for 5 minutes
• Stains: Papanicolaou (PAP), H&E, May-Grünwald-Giemsa
• Cell block technique: formalin fixation, paraffin embedding for histology sections
• Look for malignant cells, multinucleate cells, reactive mesothelial cells
• Immunocytochemistry: Calretinin (mesothelial cells), CEA, CK5/6, EMA, TTF-1 (adenocarcinoma)
• Sensitivity for malignancy: ~60-70%; specificity high

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Biochemical Investigations

Standard tests:

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Principles of Important Tests

LDH (Lactate Dehydrogenase)

• Catalyzes conversion of lactate to pyruvate
• Elevated in exudates, malignancy, hemolytic states
• Method: kinetic spectrophotometric (NADH oxidation at 340 nm)

ADA (Adenosine Deaminase)

• Enzyme involved in purine metabolism; elevated in T-lymphocyte-rich fluids
• Principle: ADA converts adenosine to inosine + NH3; ammonia measured colorimetrically (Berthelot reaction)
• Cut-off for pleural TB: >40 U/L; peritoneal TB: >36 U/L

Amylase

• Measured by substrate hydrolysis (starch-iodine or p-nitrophenyl methods)
• Elevated in pancreatitis (peritoneal/pleural), esophageal rupture

Glucose

• Oxidase or hexokinase method
• Low glucose (<60 mg/dL or fluid:serum ratio <0.5): bacterial infection, rheumatoid arthritis, TB, malignancy

pH

• Measured with blood gas analyzer
• Pleural pH <7.2 indicates need for drainage; pH <7.0 in peritoneal fluid suggests bacterial peritonitis

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Light's Criteria (for Pleural Fluid - Exudate)

• Sensitivity: ~98% for exudates
• Specificity: ~83% (some transudates misclassified - "Light's criteria misidentification" in CHF patients on diuretics)
• Corrective: Serum-effusion albumin gradient >1.2 g/dL → reclassify as transudate even if Light's criteria met

SAAG (Serum-Ascites Albumin Gradient) for ascitic fluid:

• SAAG = Serum albumin - Ascitic fluid albumin
• SAAG ≥1.1 g/dL: portal hypertension (cirrhosis, CCF) - transudate physiology
• SAAG <1.1 g/dL: malignancy, TB peritonitis, pancreatitis - exudate physiology

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Automated Fluid Analysis

• Modern analyzers (Sysmex XN, Abbott Hematology, Beckman Coulter): dedicated body fluid modes
• Use fluorescent laser scatter (VCS technology) to differentiate cell types
• Provide: TNC (total nucleated cell count), RBC count, mononuclear/polymorphonuclear cell differentiation
• Advantages: rapid, reproducible, reduces manual counting errors
• Limitations: may misclassify atypical cells; malignant cells still require cytology
• Sysmex XN-series: WDF channel uses side-fluorescence and forward scatter; body fluid (BF) mode gives differential with flags for abnormal cells

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Q14. Complete CSF Examination

Introduction

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Collection

Procedure - Lumbar Puncture:

• Patient positioned: lateral decubitus (fetal position) or sitting forward-flexed
• Site: L3-L4 or L4-L5 interspace (below the conus medullaris at L1)
• Sterile technique: Betadine, sterile draping, local anesthetic
• Spinal needle (20-22G) introduced until CSF flows
• Opening pressure measured (normal: 70-180 mmH2O lateral decubent; up to 250 in obese)
• Collect 3-4 tubes: Tube 1 = biochemistry, Tube 2 = microbiology, Tube 3 = cell count, Tube 4 = special tests
• Contraindications: raised ICP with papilledema, posterior fossa mass, coagulopathy (INR >1.5, platelets <50,000), local infection at LP site, uncorrected coagulopathy

Specimen Handling:

• Process immediately (cells deteriorate within 1 hour)
• Store at room temperature for cell count (not refrigerated)
• Glucose must be compared with simultaneous blood glucose

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Physical Examination

Xanthochromia:

• Yellow discoloration due to: oxyhemoglobin (within hours), bilirubin (>12h post-bleed), carotenoids, high protein
• Critical for distinguishing subarachnoid hemorrhage from traumatic tap
• Traumatic tap: blood decreases from tube 1 to tube 4; no xanthochromia in supernatant
• SAH: blood in all tubes equally; xanthochromia in centrifuged supernatant

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Cell Count and Differential

Normal Values:

Methods:

• Manual: Fuchs-Rosenthal hemocytometer (preferred over Neubauer for low counts) - holds 3.2 µL; count all cells in 16 large squares, divide by 3.2
• Count performed undiluted usually (or 1:1 dilution with saline for bloody specimens)
• Differential: cytocentrifuge preparation, stained with Wright-Giemsa or PAP

Differential Cell Interpretation:

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Biochemical Tests

Normal Values:

Protein:

• Methods: Turbidimetric (TCA precipitation), dye-binding (Coomassie brilliant blue or Pyrogallol red), Biuret, colorimetric
• Elevated protein (>45 mg/dL):
  • Moderate elevation (45-500 mg/dL): bacterial meningitis, Guillain-Barré syndrome, diabetic neuropathy, MS
  • Very high (>500 mg/dL): bacterial meningitis, Froin's syndrome (spinal block - CSF clots spontaneously, CSF is yellow and gelatinous)
  • Froin's syndrome: protein >1000 mg/dL, xanthochromic, spontaneous coagulation, cell count normal

Glucose:

• Method: Glucose oxidase or hexokinase
• Low glucose (hypoglycorrhachia, <40 mg/dL or CSF:plasma ratio <0.5):
  • Bacterial meningitis (bacteria/PMNs consume glucose)
  • TB meningitis (slowly falling glucose - characteristic)
  • Fungal meningitis
  • Carcinomatous meningitis
  • Normal in viral meningitis (usually)
• High glucose: hyperglycemia, diabetes mellitus

CSF Glutamine:

• Elevated in hepatic encephalopathy (ammonia converted to glutamine in brain)
• Normal: 8-18 mg/dL; >35 mg/dL = hepatic coma

IgG Index (for demyelination):

• Formula: (CSF IgG / Serum IgG) ÷ (CSF Albumin / Serum Albumin)

• 0.7 indicates intrathecal IgG synthesis (seen in MS)

• Oligoclonal bands (OCB): detected by isoelectric focusing; present in >95% of MS cases; also in CNS infections, neurosarcoidosis

CSF Lactate:

• Method: enzymatic (lactate dehydrogenase)

• 3.5 mmol/L: bacterial meningitis; helps distinguish from viral (usually <2.1 mmol/L)

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Microbiological Examination

Gram Stain:

• Sensitvity: 60-90% in bacterial meningitis (lower with prior antibiotics)
• Centrifuge 1-2 mL at 3000 rpm, use deposit

Common organisms and findings:

India Ink Preparation:

• Mix 1 drop CSF + 1 drop India ink; capsule appears as clear halo around dark yeast cells
• Sensitivity: 50-80% in HIV patients
• Specificity: high (avoid confusion with fat droplets, lymphocytes)

Cryptococcal Antigen (CrAg):

• Latex agglutination or lateral flow assay
• Sensitivity: >90%; faster than culture

Culture:

• Blood agar, chocolate agar (for fastidious organisms), Sabouraud's (fungi)
• Incubate at 37°C for 48-72 hours (bacteria), 4-6 weeks (mycobacteria)
• BACTEC/MGIT system for faster mycobacterial culture

PCR:

• Herpes simplex encephalitis: HSV-1/2 PCR (test of choice)
• Enteroviral meningitis: Enterovirus PCR
• TB meningitis: MTB PCR (sensitivity ~50-80%)
• Cryptococcal/fungal: PCR less commonly used

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Interpretation in Different Diseases

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Automated CSF Analysis

• Cell counters with body fluid mode (Sysmex, Beckman, Abbott): provide TNC, MNC/PMN differentiation, RBC count
• Iris iQ200: image-based automated urinalysis/CSF analyzer using flow imaging; digital images for each cell type
• CellaVision DM: automated digital microscopy; WBC differential with AI-assisted classification
• Advantages: rapid, objective, reproducible, flags atypical cells
• Limitations: cannot replace cytomorphology for malignant cells; limited sensitivity for rare cells (blasts, plasma cells)
• CSF multiplex PCR panels (BioFire FilmArray Meningitis/Encephalitis Panel): detects 14 pathogens simultaneously in ~1 hour

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Q15. APTT (Activated Partial Thromboplastin Time)

Introduction

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Principle

1. Patient plasma (platelet-poor) is mixed with:
   • A phospholipid (partial thromboplastin - acts as platelet substitute)
   • A contact activator (activates factor XII/XI - the "intrinsic" initiating step)
2. Incubated for a contact activation phase (~3 minutes at 37°C)
3. CaCl2 is added to recalcify (calcium was removed when blood was drawn into sodium citrate)
4. Time from CaCl2 addition to clot formation is measured

• The "partial" in the name refers to using phospholipid without tissue factor (a "complete" thromboplastin would include tissue factor and measure the extrinsic pathway)
• Activates: XII → XIa → IXa → VIIIa → X → Xa → II (thrombin) → fibrin

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Reagents

• Combined reagent = Cephaloplastin (phospholipid + activator)
• Different commercial reagents have different sensitivities to heparin and lupus anticoagulant

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Procedure (Manual)

1. Collect blood in 3.2% sodium citrate (9:1 blood:anticoagulant ratio)
2. Centrifuge at 2500-3000g for 15 min → platelet-poor plasma (PPP)
3. Add 0.1 mL PPP + 0.1 mL cephaloplastin reagent in test tube
4. Incubate at 37°C for 3 minutes (contact activation)
5. Add 0.1 mL prewarmed 0.025 M CaCl2
6. Start stopwatch; tilt tube every 5 seconds; note time of clot formation
7. Perform in duplicate; report the average

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Normal Range

• Normal APTT: 28-40 seconds (varies with reagent/analyzer; each lab must establish its own range)
• Therapeutic heparin range: 1.5-2.5× the mean normal APTT (typically 60-100 seconds)
• A ratio (patient APTT / mean normal APTT) >1.5 is considered prolonged

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Factors Assessed by APTT

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Causes of Prolonged APTT

Single factor deficiency (<30% of normal):

• Hemophilia A: Factor VIII deficiency (most common hereditary coagulopathy)
• Hemophilia B: Factor IX deficiency (Christmas disease)
• Factor XI deficiency (Hemophilia C - Rosenthal syndrome)
• Factor XII, prekallikrein, HMWK deficiency: prolonged APTT but NO bleeding (not clinically significant)

• Factor X, V, II, I (fibrinogen) deficiency → both APTT and PT prolonged

• Heparin therapy (unfractionated heparin)
• Lupus anticoagulant (LA): antiphospholipid antibody - inhibits phospholipid-dependent reactions; paradoxically associated with thrombosis
• Disseminated Intravascular Coagulation (DIC): consumption of factors V, VIII, fibrinogen
• Liver disease: decreased synthesis of all clotting factors
• Vitamin K deficiency (affects II, VII, IX, X): APTT and PT both prolonged
• Massive transfusion
• Direct thrombin inhibitors (dabigatran, argatroban): prolong APTT

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Mixing Study (Correction Study)

1. Mix patient plasma 1:1 with Normal Pooled Plasma (NPP)
2. Incubate at 37°C for immediate reading and 1-hour incubation
3. Measure APTT of mixture

• APTT corrects (mixture APTT within 10 seconds of NPP): factor deficiency (NPP provides the missing factor)
• APTT does not correct: inhibitor present

Inhibitor types:

• Immediate-acting inhibitor: factor-specific inhibitor (e.g., Factor VIII inhibitor in acquired hemophilia A) - inhibition visible immediately
• Time-dependent inhibitor: lupus anticoagulant (LA) - inhibition more pronounced after 1-hour incubation; factor VIII inhibitor is also time-dependent

Rosner Index:

• % Correction = [(APTT mix - APTT normal) / APTT patient] × 100

• 15%: inhibitor present; <15%: factor deficiency

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Automated Coagulation Analyzers

Principles of detection:

1. Electromechanical (tilt-tube / ball-movement): fibrin forms and impedes ball/wire movement in magnetic field; detects clot mechanically (e.g., Stago STA series - most widely used)
2. Photo-optical (turbidimetric): optical sensors detect increase in light absorbance as fibrin forms (Siemens Sysmex CA series)
3. Chromogenic: measures enzyme activity via color change of substrate (used for heparin assays, factor assays)
4. Fluorescent: fluorescent-labeled substrates

Major analyzers:

• Stago STA-R Max / STA-Satellite (electromechanical, gold standard)
• Sysmex CS-5100: photo-optical + mechanical; high-throughput
• ACL TOP (Instrumentation Laboratory): photo-optical
• Siemens BCS XP: photo-optical

Advantages of automation:

• Reproducibility, throughput, simultaneous multiple tests
• Reduced pre-analytical error
• Liquid-level sensing prevents short-sampling
• Clot detection algorithms compensate for lipemic/icteric samples

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Q16. Prothrombin Time (PT)

Introduction

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Principle

1. Patient platelet-poor plasma is recalcified with tissue factor (thromboplastin) + calcium chloride
2. Tissue factor + calcium activates factor VII → extrinsic pathway → X → Xa → II → thrombin → fibrin
3. Time from addition of thromboplastin/CaCl2 to fibrin clot formation = PT

• Factor VII (extrinsic)
• Factors X, V, II, I (common)
• NOT tested: VIII, IX, XI, XII (intrinsic pathway)

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Reagents

• ISI (International Sensitivity Index): compares reagent sensitivity to the WHO international reference thromboplastin; lower ISI = more sensitive (better for INR)
• Rabbit brain thromboplastin ISI ~2.0-3.0 (less sensitive)
• Recombinant human thromboplastin ISI ~1.0 (most sensitive)

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Procedure

1. Collect blood in 3.2% sodium citrate (9:1 ratio)
2. Centrifuge → platelet-poor plasma (PPP)
3. Pipette 0.1 mL PPP into test tube at 37°C
4. Add 0.2 mL prewarmed thromboplastin-CaCl2 reagent
5. Start timer; gently tilt tube; note time of clot formation
6. Perform in duplicate; record average
7. Simultaneously test a normal control plasma

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Calculation of INR

INR = (Patient PT / Mean Normal PT)^ISI

• Mean Normal PT = geometric mean PT of ≥20 healthy volunteers tested with the same reagent
• ISI = International Sensitivity Index of the reagent used

Therapeutic INR ranges for warfarin:

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Factors Assessed

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Clinical Applications

1. Warfarin therapy monitoring (primary use)
2. Liver disease assessment: liver synthesizes all coagulation factors; PT prolongation indicates synthetic dysfunction; used in Child-Pugh and MELD scores
3. Vitamin K deficiency: dietary deficiency, malabsorption, newborn hemorrhagic disease
4. Screening before surgical procedures
5. DIC: consumption of clotting factors
6. Factor VII, X, V, II, I deficiency screening

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Causes of Prolonged PT

Isolated PT prolongation (APTT normal):

• Factor VII deficiency (hereditary or acquired)
• Early vitamin K deficiency (VII is first to fall - shortest half-life)
• Early warfarin effect
• Liver disease (mild)

Both PT and APTT prolonged:

• Warfarin therapy (affects II, VII, IX, X)
• Vitamin K deficiency (affects II, VII, IX, X)
• Liver disease (decreased synthesis of all factors)
• DIC (consumption of factors V, VIII, fibrinogen, plus vitamin K-dependent factors)
• Deficiency of factors X, V, II, or fibrinogen (common pathway)
• Direct oral anticoagulants (DOACs): factor Xa inhibitors (rivaroxaban, apixaban) prolong PT mildly
• Massive transfusion (dilutional coagulopathy)
• Dysfibrinogenemia / hypofibrinogenemia

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Automated Estimation

• Same analyzers as APTT (Stago STA series, Sysmex CS-5100)
• Automated dispensing of plasma + reagent + CaCl2 at precise volumes
• Optical/electromechanical clot detection
• Auto-INR calculation: analyzer applies ISI and MNPT to compute INR directly
• POC (Point-of-care) INR: CoaguChek (Roche), i-STAT (Abbott) - fingerprick whole blood; used for patient self-monitoring of warfarin
• POC INR uses electrochemical or optical detection of fibrin formation in capillary
• Results available in <2 minutes

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Q17. ABO and Rh Blood Grouping

Introduction

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ABO Blood Group System

Genetics:

• ABO gene on chromosome 9; encodes glycosyltransferases that add sugar residues to H antigen (the precursor substance, produced by H gene on chromosome 19)
• A gene: adds N-acetylgalactosamine to H → A antigen
• B gene: adds D-galactose to H → B antigen
• O allele: amorph - no transferase activity → H antigen remains unconverted

Blood groups and antigens/antibodies:

• ABO antibodies are naturally occurring (IgM, formed by exposure to environmental antigens)
• Bombay blood group (Oh): No H antigen; serum contains anti-H, anti-A, anti-B; only compatible with other Bombay donors

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Forward and Reverse Grouping

Forward (Direct) Grouping:

• Tests RBC antigens using known antisera
• Mix patient RBCs + anti-A serum → agglutination = A antigen present
• Mix patient RBCs + anti-B serum → agglutination = B antigen present
• Mix patient RBCs + anti-AB serum → confirms grouping
• Mix patient RBCs + anti-H lectin (Ulex europaeus) → tests H antigen

Reverse (Indirect/Serum) Grouping (Back typing):

• Tests serum antibodies using known group A1 and B reagent RBCs
• Mix patient serum + A1 RBCs → agglutination = anti-A present
• Mix patient serum + B RBCs → agglutination = anti-B present
• Results must confirm forward grouping (Landsteiner's rule)

Interpretation:

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Rh Blood Group System

D Antigen:

• Most immunogenic Rh antigen; located on chromosome 1 (RHD gene)
• Rh-positive: D antigen present on RBCs (~85% of Caucasians, ~97% of South Asians)
• Rh-negative: D antigen absent; RHD gene deleted
• Unlike ABO, Rh antibodies are NOT naturally occurring; they are immune (formed after exposure to D antigen via transfusion or pregnancy)
• Rh antibodies are IgG - can cross the placenta → Hemolytic Disease of the Fetus and Newborn (HDFN)

Other Rh antigens: C, c, E, e (collectively CCDEE system)

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Principles of Grouping

Agglutination reaction:

• Two-stage process:
  1. Sensitization: antibody coats RBC (best at 4°C for IgM, 37°C for IgG)
  2. Agglutination: lattice formation cross-linking coated RBCs
• IgM = directly agglutinating (saline agglutinins) - detectable in tube/slide tests
• IgG = incomplete antibodies - require enhancement (albumin, LISS, AHG) for detection

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Reagents

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Procedure

Tube Method (standard):

1. Label tubes: anti-A, anti-B, anti-D (for Rh)
2. Add 1 drop of appropriate antiserum to each tube
3. Add 1 drop of 2-5% RBC suspension in saline
4. Mix gently; centrifuge at 1000 rpm for 1 minute
5. Resuspend gently; read for agglutination (0 to 4+ grading)

Tile/Slide Method (emergency/rapid):

1. Place 1 drop antiserum on labeled tile
2. Add 1 drop of 40-50% RBC suspension (washed cells)
3. Mix with stick; rock gently for 2 minutes; read in good light

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Interpretation and Grading of Agglutination

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Discrepancies in ABO Grouping

Forward/reverse discordance causes:

• Subgroups of A (A2, A3, Ax, Aend) - weaker antigen expression
• Leukemia (acquired loss/weakening of blood group antigens)
• Chimerism
• Old/hypotonic cells

• Neonates (ABO antibodies not fully developed; test forward group only)
• Elderly, hypogammaglobulinemia
• Bone marrow transplant
• Bombay phenotype (agglutinates all cells)

• Polyagglutinable cells (T-activation)
• Cold agglutinins
• Wharton's jelly contamination in cord blood
• Rouleaux formation (elevated protein)

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Weak D Testing

• Some individuals have reduced D antigen expression (weak D, Du phenotype): fail to type as D+ by routine IgM anti-D but carry D antigen
• Testing: perform indirect antiglobulin test (IAT) with anti-D (IgG phase)
• Procedure: incubate patient cells + anti-D at 37°C → wash → add AHG → centrifuge → read
• Clinical significance: Weak D individuals as blood donors = type as D+ (can immunize D- recipients); as patients = can safely receive D+ blood

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Automated Blood Grouping Systems

• Column agglutination technology (CAT) / Gel cards (Bio-Rad ID-Cards, Grifols DG Gel):
  • Microcolumns filled with dextran-acrylamide gel + antisera
  • Cells centrifuged into gel: agglutinated cells remain at top/middle; non-agglutinated cells pellet at bottom
  • Read visually or by automated scanner (Bio-Rad IH-500, Grifols Erytra)
• Solid-phase red cell adherence (SPRCA) (Capture-R, Immucor): RBC antigens or antibodies immobilized on microplate wells; read by automated imaging
• Automated tube systems: Ortho AutoVue, ImmucorGamma
• High-throughput processing; digital result storage; reduced transcription errors

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Q18. Compatibility Testing / Cross-Matching

Introduction

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Principle

• Based on antigen-antibody reactions causing agglutination or hemolysis
• Detects incompatibilities that may cause immune destruction of transfused RBCs
• Must include testing at multiple phases (immediate spin, 37°C, AHG) to detect different antibody classes

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Types

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Procedure (Full Cross-Match)

Phase 1 - Immediate Spin (IS):

1. Mix 2 drops patient serum + 1 drop 3-5% donor RBC suspension
2. Centrifuge at 1000 rpm for 30 seconds
3. Resuspend; read for agglutination/hemolysis
4. Detects IgM antibodies (mainly ABO antibodies)

Phase 2 - 37°C Incubation:

1. Add enhancement media (LISS or albumin) to above tube
2. Incubate at 37°C for 15-30 minutes
3. Centrifuge; read
4. Detects IgG antibodies that bind at body temperature

Phase 3 - AHG (Indirect Antiglobulin Test / Coombs Phase):

1. Wash cells 3× with saline (removes unbound antibody)
2. Add AHG (anti-human globulin reagent)
3. Centrifuge 1000 rpm for 1 minute; read
4. Add IgG-coated check cells (Coombs control cells) if negative → must agglutinate to validate the wash step
5. Detects IgG antibodies, complement-fixing antibodies

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Interpretation

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Major vs Minor Cross-Match

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Immediate Spin vs AHG Cross-Match

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Electronic/Computer Cross-Match

• No serological testing with donor cells
• Requirements: patient must have TWO historical ABO/Rh groups on record; current antibody screen negative
• Computer verifies ABO/Rh compatibility of donor with patient
• Cannot detect: irregular antibodies (but antibody screen is negative by definition)
• Fastest method; safe when antibody screen is negative and ABO is confirmed

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Gel Card (Column Agglutination) Cross-Match

• Neutral gel cards (no AHG) for IS phase
• AHG gel cards contain polyclonal/monoclonal AHG
• Procedure: add patient serum and donor RBCs to microcolumn; incubate; centrifuge
• Agglutinated cells trapped in gel = incompatible
• Free cells pellet at bottom = compatible
• Standardized, reproducible, storable results (photographed)
• Less technical variation than tube method

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Q19. Direct Antiglobulin Test (DAT)

Introduction

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Principle

• Patient RBCs are coated with IgG and/or complement in vivo (e.g., autoimmune hemolytic anemia)
• Wash RBCs to remove unbound serum proteins
• Add AHG reagent (anti-human globulin - contains anti-IgG and/or anti-C3d)
• AHG bridges IgG-coated RBCs → visible agglutination = positive DAT

The key concept: in DAT, no exogenous antibody is added because the antibody is already on the RBCs.

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Specimen

• EDTA blood (preferred): prevents complement fixation in vitro (which would give false-positive C3 result)
• Venous blood, fresh (ideally <6 hours)
• Do NOT use clotted blood (serum activates complement in vitro)
• In neonates: cord blood or venous blood

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Reagents

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Procedure

1. Wash patient RBCs 3-4 times with large volumes of saline (critical step - removes unbound globulin)
2. Decant wash saline completely each time
3. Add 2 drops polyspecific AHG to washed RBC button
4. Mix; centrifuge at 1000 rpm for 1 minute
5. Resuspend gently; read for agglutination (0 to 4+)
6. If negative: add IgG-coated check cells → must give 1-2+ agglutination (validates that AHG is active and wash was adequate)
7. If check cells fail to agglutinate when DAT is negative → test is invalid; repeat

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Interpretation

Grading significance:

• 1+ or 2+: significant; may be associated with hemolysis
• 3+ or 4+: strongly positive; marked hemolysis

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Clinical Indications

1. Autoimmune Hemolytic Anemia (AIHA) - diagnosis
2. Hemolytic Transfusion Reaction - investigation
3. Hemolytic Disease of the Fetus and Newborn (HDFN) - cord blood DAT
4. Drug-induced hemolytic anemia - penicillin, cephalosporins, methyldopa, quinine
5. Investigate unexplained hemolysis/anemia

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Causes of Positive DAT

Warm AIHA (IgG, 37°C):

• Idiopathic
• CLL, lymphoma (secondary)
• SLE, other autoimmune diseases
• Methyldopa, fludarabine, cephalosporins

Cold AIHA (IgM-mediated, C3d on RBCs):

• Mycoplasma pneumoniae infection (anti-I antibodies)
• Infectious mononucleosis (anti-i)
• Idiopathic (cold agglutinin disease)

Paroxysmal Cold Hemoglobinuria (PCH):

• IgG Donath-Landsteiner antibody (anti-P)
• Syphilis (historically), post-viral in children
• Biphasic: fixes complement at cold, lyses at 37°C
• DAT: positive for C3d only

Drug-induced hemolytic anemia:

• Hapten mechanism (penicillin, cephalosporins): drug coats RBCs; anti-drug IgG → DAT positive for IgG
• Immune complex mechanism (quinine, quinidine): drug-antibody complex fixes complement on RBCs → DAT positive for C3d
• Autoantibody mechanism (methyldopa, fludarabine): drug induces true autoantibody → DAT positive for IgG

Hemolytic Transfusion Reaction:

• Recipient alloantibody coats transfused RBCs
• DAT positive for IgG (and often C3d)

HDFN:

• Maternal IgG (anti-D, anti-c, anti-K, anti-E) crosses placenta
• Coats fetal/neonatal RBCs → positive DAT in cord blood

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Sources of Error

• Clotted blood or delayed testing (in vitro complement activation)
• Over-centrifugation
• Mechanical fragility of cells
• Polyagglutination
• Previous IV immunoglobulin therapy
• Hypergammaglobulinemia (nonspecific protein coating)

• Inadequate washing (unbound globulin neutralizes AHG)
• Inactive or deteriorated AHG reagent (validated by check cells)
• Low antibody density (<200 IgG molecules/RBC)
• Prozone effect (very high antibody concentration)
• Complement inhibitors in EDTA tube interfering with C3 detection

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Gel/Column Agglutination Method (Bio-Rad DAT-Cards)

• Gel card contains AHG (anti-IgG + anti-C3d or monospecific)
• Add washed RBC suspension to well; centrifuge
• Agglutinated cells (positive) = trapped in gel or at top
• Free cells (negative) = pellet at bottom
• Advantages: standardized, reproducible, storable images, no wash step errors, automated reading
• Sensitivity: similar to or better than tube method for detecting weak sensitization
• Monospecific DAT gel cards: anti-IgG and anti-C3d columns available separately for further characterization

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Q20. Indirect Antiglobulin Test (IAT)

Introduction

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Principle

1. Sensitization stage: Patient serum is incubated with reagent RBCs at 37°C → if antibody present, it coats the RBCs (in vitro)
2. AHG stage: Wash cells to remove unbound antibody → add AHG → if IgG-coated cells present, AHG bridges them → agglutination

Key distinction from DAT: In IAT, sensitization is performed IN VITRO using patient serum; in DAT, cells are already sensitized IN VIVO.

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Procedure

Stage 1 - Sensitization:

1. Add 2-3 drops patient serum to tube
2. Add 1 drop 2-5% reagent RBC suspension (group O cells with known antigen profile)
3. Add enhancement media (LISS - Low Ionic Strength Solution, or albumin)
4. Incubate at 37°C for 15-30 minutes (LISS) or 30-60 minutes (albumin)
5. Centrifuge; read and record IS and 37°C reactivity

Stage 2 - AHG:

1. Wash cells 3-4× with large volumes saline (critical)
2. Decant wash completely
3. Add 2 drops AHG to cell button
4. Mix; centrifuge 1000 rpm × 1 minute
5. Resuspend; read for agglutination
6. Add check cells if negative → must agglutinate

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Enhancement Media

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AHG Reagent

• Polyclonal AHG made in rabbits (immunized with human globulin)
• Monoclonal AHG: higher specificity, consistency

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Interpretation

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Clinical Applications

1. Antibody Screening (Indirect Coombs Screen):

• Patient serum tested against 2-3 group O screening cells with known antigen expression (covering common clinically significant antigens)
• Positive screen: proceed to antibody identification
• Performed pre-transfusion, in pregnant women, and before surgery
• Reagent cell panels: include antigens for Rh (D, C, c, E, e), Kell (K, k), Duffy (Fya, Fyb), Kidd (Jka, Jkb), MNS system

2. Antibody Identification:

• Screen-positive serum tested against panel of 8-16 group O cells (antibody identification panel) with known antigen profiles
• Pattern of reactivity identifies the antibody specificity
• Rules for identification:
  • Include cells: all cells positive must have the antigen in common
  • Exclude cells: all negative cells should lack the antigen
  • Minimum 3 positive + 3 negative cells required for certainty (Fisher's exact test: p<0.05)

3. Pre-transfusion Testing (Cross-Match AHG Phase):

• Patient serum vs donor RBCs; AHG phase detects IgG incompatibility

4. Antenatal Screening:

• All pregnant women screened at booking and 28 weeks
• Identifies alloantibodies (anti-D, anti-c, anti-K, anti-E) that can cause HDFN
• Titration performed if antibody found (≥1:16 suggests risk of severe HDFN)

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Automated and Gel Techniques

Gel Column Technology (Bio-Rad / Grifols):

• AHG gel cards used for both IAT and DAT
• Sample preparation: serum + cells incubated, then transferred to AHG column
• Centrifugation separates agglutinated from free cells
• Automated readers (Bio-Rad IH-500, Grifols Erytra Flex) image and score results
• Benefits: standardized, storable, objective, reduced variability

Solid-Phase Red Cell Adherence (SPRCA):

• Patient serum added to wells coated with reagent RBC membranes (for antibody screen) or RBC stroma
• Indicator cells (IgG-coated RBCs) added
• If antibody present → binds to well-bound antigen → indicator cells spread = positive (no pellet)
• If no antibody → indicator cells form button pellet = negative

Automated Analyzers:

• Bio-Rad IH-500: fully automated gel card processing; 230 tests/hour
• Grifols Erytra: walk-away automation; gel + tube tests
• Ortho Vision Max: microplate-based; high throughput
• Immucor Galileo Echo: tube/microplate automation

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Q21. Laboratory Estimation of Blood Glucose

Introduction

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Sample Requirements

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Methods of Glucose Estimation

1. Glucose Oxidase Method (Reference method for plasma glucose)

Glucose + O2 → Gluconic acid + H2O2 (glucose oxidase) H2O2 + chromogen (o-dianisidine/ABTS) → colored product (peroxidase)

• Colored product measured spectrophotometrically at 505-540 nm (depending on chromogen)
• High specificity for glucose (glucose oxidase acts only on beta-D-glucose)
• Interference: high ascorbic acid (inhibits peroxidase reaction) → falsely low; uric acid, bilirubin → falsely low (reducing agents compete for H2O2)
• Method in POCT glucometers (electrochemical variant): glucose oxidase on electrode strip generates current proportional to glucose

2. Hexokinase Method (TRUE reference method)

Glucose + ATP → Glucose-6-phosphate (hexokinase) Glucose-6-phosphate + NADP+ → 6-phosphogluconate + NADPH (G6P dehydrogenase)

• NADPH measured at 340 nm (UV absorbance)
• Most specific and accurate method
• Not affected by galactose, fructose, or common interfering substances
• Used in automated analyzers and reference laboratories
• Basis for WHO reference method

3. Ortho-Toluidine Method (Folin-Wu modification)

• Glucose reacts with o-toluidine in hot acetic acid → blue-green color (Schiff base)
• Measured at 625 nm
• Less specific (also reacts with other sugars); largely replaced by enzymatic methods

4. Somogyi-Nelson (Reduction method - historical)

• Based on reduction of copper sulfate by glucose (Folin-Wu modification)
• Non-specific; historical use only

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Normal Values

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Glucose Tolerance Tests

Oral Glucose Tolerance Test (OGTT):

• Preparation: 3 days of unrestricted diet (≥150g carbohydrate/day); overnight fast (8-14 hours); fasting blood drawn
• Dose: 75g anhydrous glucose in 250-300 mL water, consumed in 5 minutes
• Samples: fasting and 2-hour post-load venous plasma glucose
• Additional samples at 1h in pregnancy (GDM screening)

Gestational Diabetes (GDM) Screening:

• 1-step (IADPSG/WHO 2013): 75g OGTT at 24-28 weeks; diagnose GDM if fasting ≥92, 1h ≥180, 2h ≥153 mg/dL
• 2-step (ACOG/ADA alternate): 50g GCT screen (non-fasting) → if 1h ≥130-140, proceed to 100g 3h OGTT

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HbA1c

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Point-of-Care Testing (POCT)

Glucometers:

• Strip-based: glucose oxidase or glucose dehydrogenase (GDH-PQQ or GDH-FAD) on electrochemical strip
• Current generated proportional to glucose concentration
• GDH-PQQ: may react with maltose/galactose → falsely elevated in peritoneal dialysis patients
• Capillary blood (fingerstick); results in 5 seconds
• ADA recommends plasma-calibrated glucometers

POCT HbA1c:

• Afinion, DCA Vantage: immunoturbidimetric; 3-5 minutes from fingerstick; use at clinic

Continuous Glucose Monitoring (CGM):

• Subcutaneous sensor (glucose oxidase electrode) measures interstitial glucose every 1-5 minutes
• Calibrated against capillary glucose; time-in-range reporting

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Automated Glucose Estimation

• Clinical chemistry analyzers (Beckman AU, Roche cobas, Abbott Architect, Siemens Atellica):
  • Hexokinase or glucose oxidase (UV or colorimetric) methods
  • Fully automated: sample aspiration, reagent mixing, incubation, measurement, calculation
  • QC with Westgard rules applied automatically
  • Reflex testing (if critical value → auto-repeat)
  • Throughput: 400-1000 tests/hour

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Q22. Estimation of Serum Bilirubin

Introduction

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Metabolism Recap

• Senescent RBCs → heme → biliverdin (biliverdin reductase) → unconjugated bilirubin (UCB) (indirect) - water-insoluble, albumin-bound
• UCB → liver → conjugated with glucuronic acid (UDP-glucuronosyltransferase) → conjugated bilirubin (CB) (direct) - water-soluble
• CB → bile → gut → urobilinogen → urobilin (stool), urobilin (urine)
• Delta bilirubin: CB covalently bound to albumin; long half-life (14 days); does not appear in urine

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Normal Values

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Principle - Diazo Method (Van den Bergh Reaction)

Bilirubin + Diazotized sulfanilic acid (diazo reagent) → Azobilirubin (pink/red-purple)

• Direct bilirubin (conjugated): reacts rapidly with diazo reagent in aqueous solution in 1 minute at room temperature (without accelerator) → "direct-reacting"
• Indirect bilirubin (unconjugated): does not react in aqueous medium; requires an accelerator (methanol, caffeine-benzoate, Triton X-100) to displace UCB from albumin and allow reaction → "indirect-reacting"
• Total bilirubin: measured after adding accelerator (measures both direct + indirect)
• Indirect bilirubin = Total - Direct

Diazo Reagent preparation:

• Sulfanilic acid + HCl + NaNO2 → Diazotized sulfanilic acid
• Must be freshly prepared; used within 30 minutes

Malloy-Evelyn method:

• Uses methanol as accelerator
• Reads at 540 nm

Jendrassik-Grof (J-G) method (most commonly used in clinical labs):

• Accelerator: caffeine-benzoate (caffeine + sodium benzoate + sodium acetate)
• Fading reagent: diphylline (alkaline)
• Measured at 600 nm (blue-green color)
• More specific than Malloy-Evelyn; less affected by hemolysis and lipemia
• J-G method is the IFCC reference method

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Procedure (J-G Method)

Direct bilirubin (without caffeine):

1. Add patient serum + sulfanilic acid reagent
2. Add diazo reagent → mix; incubate 5 min at RT
3. Add Fehling's solution → read absorbance at 600 nm within 1 minute

Total bilirubin (with caffeine-benzoate):

1. Add patient serum + caffeine-benzoate reagent
2. Add diazo reagent → incubate 10 min at RT
3. Add fading reagent (diphylline) → measure at 600 nm
4. Indirect = Total - Direct

Calibration:

• Standards: Calibrated serum standards with known bilirubin values
• Blank (reagent blank): replace diazo reagent with sulfanilic acid in HCl (no NaNO2)

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Direct vs Indirect Bilirubin

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Causes of Hyperbilirubinemia

Predominantly Indirect (Unconjugated):

• Hemolysis (pre-hepatic)
• Gilbert's syndrome (mild unconjugated): reduced UGT1A1 activity (~10-30% of normal)
• Crigler-Najjar syndrome Type I/II (severe/moderate deficiency of UGT1A1)
• Neonatal physiological jaundice (immaturity of conjugating enzymes)
• Ineffective erythropoiesis (dyserythropoiesis)

Predominantly Direct (Conjugated):

• Hepatocellular: hepatitis (viral, autoimmune, alcoholic), cirrhosis - mixed increase
• Cholestatic (obstructive):
  • Intrahepatic: primary biliary cholangitis (PBC), PSC, drugs, pregnancy (ICP)
  • Extrahepatic: choledocholithiasis, pancreatic cancer, cholangiocarcinoma
• Dubin-Johnson syndrome: defect in MRP2 (ABCC2) conjugated bilirubin transport into bile; CB accumulates; benign
• Rotor syndrome: defect in OATP1B1/1B3 uptake transporters

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Sources of Error

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Automated Bilirubin Estimation

• Chemical diazo (Jendrassik-Grof) fully automated on Beckman AU series, Roche cobas, Abbott Architect
• Direct Spectrophotometric (2-wavelength): some analyzers measure bilirubin directly using the absorbance of bilirubin at 455 nm and correct for Hb at 575 nm (no diazo needed); less specific but fast
• Dry chemistry (Fuji, Vitros): slide-based reflectometry using dried diazo reagents
• Transcutaneous bilirubinometer (TcB): Masimo, Dräger - for neonates; multiwavelength spectroscopy through skin; no blood sampling; excellent screening tool for neonatal jaundice; must confirm with serum bilirubin if elevated
• All automated methods apply reagent blanks, 2-point calibration, Westgard QC rules

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Q23. Estimation of Serum Creatinine

Introduction

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Sample Requirements

• Serum or plasma (lithium heparin)
• Stable for 7 days at 2-8°C; 1 day at room temperature
• Avoid: EDTA plasma (small dilution error); hemolysis (slight interference)

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Methods

1. Jaffe Method (Alkaline Picrate / Colorimetric Method) - Most widely used

Creatinine + Picric acid (alkaline medium) → Red-orange Janovsky complex Measured at 490-510 nm

1. Protein-free filtrate of serum prepared (Folin-Wu: tungstate/ZnSO4 precipitation) - for older manual methods
2. For automated: serum reacts directly with alkaline picrate
3. Add sample to alkaline picrate solution (NaOH + picric acid)
4. Incubate; read absorbance at 510 nm (endpoint or kinetic)
5. Kinetic (rate) Jaffe: measures rate of color formation in the first 20-80 seconds after mixing (before non-creatinine chromogens react fully) → more specific

• Endpoint Jaffe: less specific; non-creatinine chromogens (ketones, glucose, acetoacetate, protein) also react
• Kinetic (rate) Jaffe: reads during "window" of creatinine-specific reaction; more specific; standard on modern analyzers

• Acetoacetate (falsely elevated in DKA)
• Glucose (high concentrations falsely elevate)
• Pyruvate, ascorbic acid, bilirubin
• Non-specific proteins
• Lipemia: may falsely decrease (turbidity correction)

2. Enzymatic Method (Creatinine + Creatinase/Sarcosine oxidase cascade)

Creatinine + H2O → Creatine (creatinine amidohydrolase / creatinine iminohydrolase) Creatine + H2O → Sarcosine + Urea (creatine amidinohydrolase) Sarcosine + O2 → Glycine + HCHO + H2O2 (sarcosine oxidase) H2O2 + chromogen (TOOS + 4-aminoantipyrine) → colored product (peroxidase)

• Measured at 560 nm
• Highly specific; minimal interference from chromogens
• More expensive reagents
• Preferred in: neonates, diabetic ketoacidosis, patients with high bilirubin
• Some platforms also use creatinine iminohydrolase pathway (measures ammonia)

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Normal Values

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Factors Affecting Creatinine

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Clinical Significance

• Elevated creatinine (azotemia):
  • Pre-renal: dehydration, CCF, hemorrhage (↓GFR due to ↓renal perfusion)
  • Renal (intrinsic): glomerulonephritis, AKI, CKD
  • Post-renal: obstruction (BPH, stones, tumor)
• Creatinine doubles when GFR is halved (not sensitive for early GFR reduction - GFR must fall >50% before creatinine exceeds upper normal)
• Serial measurements more informative than single values (AKI definition uses rise of ≥0.3 mg/dL within 48h)

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eGFR (Estimated Glomerular Filtration Rate)

CKD-EPI Creatinine Equation (2021 - without race variable):

eGFR = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^(-1.200) × 0.9938^Age × (1.012 if female)

MDRD (Modification of Diet in Renal Disease):

eGFR = 175 × (Scr)^-1.154 × Age^-0.203 × 0.742 (if female) × 1.212 (if Black)

CKD Staging (KDIGO):

Cystatin C:

• Better marker of GFR; not affected by muscle mass
• CKD-EPI Cystatin C or CKD-EPI Creatinine-Cystatin C combined equation more accurate
• 24-hour urine creatinine clearance: GFR approximation = (Urine Cr × Volume) / (Serum Cr × 1440)

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Automated Estimation

• Kinetic Jaffe or enzymatic methods run on automated clinical chemistry analyzers
• Beckman Coulter AU5800: kinetic Jaffe; compensation for bilirubin interference
• Roche cobas 8000: enzymatic creatinine assay (CREA2) preferred
• POCT (i-STAT, Stat Profile): enzymatic creatinine on whole blood cartridge; results in 3 min
• eGFR auto-calculated and reported alongside creatinine on most analyzers
• IDMS (isotope dilution mass spectrometry) traceable calibration: standardized across labs; NIST SRM 909 used; key for CKD-EPI equation validity

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Q24. Estimation of Serum Total Protein and Albumin

Introduction

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Methods for Total Protein

1. Biuret Method (Reference method for total protein)

Peptide bonds (-CO-NH-) in proteins react with Cu²⁺ in alkaline solution → purple-violet Cu-peptide complex (biuret reaction) Measured at 540-550 nm

1. Add serum + Biuret reagent (CuSO4 + sodium potassium tartrate + NaOH + KI)
2. Mix; incubate at room temperature for 10-30 minutes
3. Read absorbance at 540 nm
4. Protein concentration calculated from calibration curve (BSA or standard protein)

• KI prevents precipitation of Cu(OH)2
• Sodium potassium tartrate: chelates Cu; keeps Cu in solution
• Detects proteins with ≥2 peptide bonds; does not detect amino acids
• Standard: Bovine serum albumin (BSA)

• Lipemia (turbidity → falsely elevated)
• Hemolysis (Hb contributes to protein; falsely elevated)
• Bilirubin (absorbs at 540 nm → falsely elevated; correct with serum blank)
• Dextran (artifactual elevation)

2. Kjeldahl Method (Primary reference - not routine)

• Wet digestion of protein → converts organic N to NH4⁺ → measured by titration or Nessler's reagent
• Total N × 6.25 = protein (assumes N content of protein = 16%)
• Gold standard but tedious; used only for method validation

3. Refractometry

• Total dissolved solids (mainly protein) alter the refractive index of serum
• Semi-quantitative; used in urine and CSF; quick bedside test
• Affected by glucose, urea in excess

4. Dye-binding (Coomassie Brilliant Blue / Bradford Assay)

• Protein binds Coomassie dye → red to blue shift; measured at 595 nm
• More sensitive than Biuret; used for very low concentrations (CSF, urine)

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Methods for Albumin

1. Bromocresol Green (BCG) Method (Most common routine method)

Albumin binds BCG dye at pH 4.2 (acetate buffer) → yellow-green to blue-green shift Measured at 628 nm (or 578 nm - difference spectrophotometry)

1. Add 10 µL serum + 1 mL BCG reagent
2. Mix; read absorbance at 628 nm after 30 seconds (endpoint within 30 sec to avoid globulin binding)
3. Calculate from albumin standard calibration curve

• BCG also binds globulins at longer incubation → falsely elevated albumin (overestimates by ~5-10%)
• More prominent in conditions with very high globulins (myeloma, chronic liver disease)
• Bilirubin may cause slight decrease
• Hemolysis: slight decrease

2. Bromocresol Purple (BCP) Method

Albumin binds BCP dye at pH 5.2 → color shift measured at 603 nm

• More specific for albumin than BCG (less globulin binding)
• Better for patients with elevated globulins, renal disease
• May underestimate in some cases; not universally preferred

3. Immunoturbidimetric / Immunonephelometric Method

• Anti-human albumin antibody + albumin → immune complex → turbidity measured
• Highly specific
• Used for urine microalbumin (very sensitive; detects 3-300 mg/L)
• Expensive; used for special situations

4. Salt Fractionation (Globulin estimation):

• Globulin = Total Protein - Albumin (calculated)

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Normal Values

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A/G Ratio

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Clinical Significance

Hypoproteinemia (Total protein <6.0 g/dL):

• Decreased synthesis: liver failure, malnutrition (kwashiorkor)
• Increased loss: nephrotic syndrome (proteinuria), protein-losing enteropathy, burns
• Increased catabolism: malignancy, sepsis, hyperthyroidism
• Hemodilution: IV fluids, overhydration, heart failure

Hyperproteinemia (Total protein >8.0 g/dL):

• Dehydration/hemoconcentration: most common cause
• Increased globulins: multiple myeloma (M-protein), Waldenstrom's macroglobulinemia, chronic infection (TB, malaria), sarcoidosis, autoimmune disease

Hypoalbuminemia (<3.5 g/dL):

• Liver cirrhosis (decreased synthesis - albumin has long half-life 17-20 days; reflects chronic disease)
• Nephrotic syndrome (loss in urine)
• Protein-losing enteropathy (Crohn's, lymphangiectasia)
• Malnutrition
• Acute-phase reaction (albumin is a negative acute-phase reactant - decreases in inflammation)
• Protein-losing skin conditions (burns, exfoliative dermatitis)

Significance of albumin:

• Oncotic pressure maintenance (80% of plasma oncotic pressure)
• Transport protein (calcium, drugs, unconjugated bilirubin, fatty acids, hormones)
• Child-Pugh score for cirrhosis uses albumin (<2.8, 2.8-3.5, >3.5)
• Surgical risk: albumin <3.0 g/dL = increased operative mortality

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Sources of Error

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Automated Methods

• Biuret total protein fully automated on Beckman, Roche, Abbott, Siemens analyzers
• BCG or BCP albumin simultaneously automated; reflexed to calculate globulin
• Automated reporting: A/G ratio auto-calculated; delta check applied
• Protein electrophoresis (SPE): serum proteins separated by charge/size on agarose gel or capillary electrophoresis (Sebia Capillarys); fractions: albumin, alpha-1, alpha-2, beta (beta-1, beta-2), gamma
  • Automated capillary zone electrophoresis (Sebia Capillarys 2): all steps automated; quantitative fractions + M-protein detection
  • Used to detect M-protein (paraprotein) in myeloma, MGUS
• Immunofixation electrophoresis (IFE): SPE followed by application of class-specific antisera; identifies immunoglobulin heavy + light chain type of M-protein
• Urine total protein: Biuret (if concentrated), pyrogallol red (more sensitive), sulfosalicylic acid turbidity
• Microalbumin (urine): immunoturbidimetric or immunonephelometric; normal <30 mg/g creatinine; microalbuminuria: 30-300 mg/g (early diabetic nephropathy)

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