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Pathology Instruments - Complete Answers

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Image 1 & 2 — Hematology Analyzer (Cell Counter)

1. Identify the Machines? What are their uses?

• Complete Blood Count (CBC) - measures RBC, WBC, platelets, hemoglobin, hematocrit
• Differential leukocyte count (automated)
• Red cell indices: MCV, MCH, MCHC, RDW
• Platelet indices: MPV, PDW, PCT
• Reticulocyte count (in advanced models)
• Screening of peripheral blood for abnormal cells (flagging)

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2. What is the meaning of 3-Part and 5-Part Coulter (Differential)?

• Separates WBCs into only 3 populations: Lymphocytes, Monocytes, and Granulocytes (neutrophils + eosinophils + basophils combined)
• Uses impedance (electrical resistance) alone based on cell size
• Less accurate; cannot distinguish neutrophils, eosinophils, and basophils separately
• Cheaper; used in smaller/peripheral labs

• Separates WBCs into 5 populations: Neutrophils, Lymphocytes, Monocytes, Eosinophils, Basophils
• Uses a combination of methods: Impedance + Light scattering (flow cytometry) + Chemical lysis + Radiofrequency
• More accurate and clinically informative
• Detects abnormal/immature cells and gives flags for manual review
• Standard in tertiary care hospitals

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Image 3 — Automated Hematology Analyzer (second model)

A. Identify the machine. What are its uses?

B. What is the meaning of 5-Part Coulter?

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Image 4 — Vacutainer System

A. Identify the instrument

B. Different Vacutainer tubes and their uses

C. Ratio of sodium citrate used in coagulation studies

D. Ratio of sodium citrate used in ESR studies

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Image 5 — Urinometer

A. Identify the instrument and its different parts

1. Glass cylinder (container for urine)
2. Graduated float (the urinometer bulb/stem)
3. Scale - graduated from 1.000 to 1.040
4. Lead ballast at the bottom of the float
5. Thermometer (in some models)

B. Principle and normal value of specific gravity

C. Corrections for temperature, protein, and glucose

• Temperature: Add 0.001 for every 3°C above 15°C; subtract 0.001 for every 3°C below 15°C
• Protein: Subtract 0.003 for every 1 g/dL of protein present
• Glucose: Subtract 0.004 for every 1 g/dL of glucose present

D. What is isosthenuria?

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Image 6 — Neubauer Counting Chamber + Pipettes (Diluting Pipettes)

A. Identify the instruments

B. Name any 2 diluting fluids for RBC count and dilution used

1. Hayem's fluid - dilution 1:200 (draw blood to 0.5 mark, fluid to 101 mark on RBC pipette)
2. Normal saline (0.9% NaCl) - dilution 1:200
3. (Also used: Gower's solution, Dacie's fluid)

C. Composition of Hayem's fluid

• Sodium sulphate: 5 g
• Sodium chloride: 1 g
• Mercuric chloride: 0.5 g
• Distilled water: 200 mL

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Image 7 — Colorimeter / Hemoglobinometer / Photoelectric Colorimeter

A. Instrument and its parts

1. Light source (tungsten lamp)
2. Filter (selects specific wavelength)
3. Cuvette/sample holder
4. Photodetector (photocell)
5. Galvanometer/display
6. Zero adjustment knob
7. Wavelength selector

B. Other different methods for Hb estimation

1. Sahli's acid hematin method (older)
2. Oxyhaemoglobin method
3. Alkaline hematin method
4. Gasometric method
5. Iron content method
6. Cyanmethemoglobin (HiCN) method - reference/gold standard

C. Principle

D. Components of Drabkin's solution

• Potassium ferricyanide (K₃Fe(CN)₆) - 200 mg: oxidizes Hb to methemoglobin
• Potassium cyanide (KCN) - 50 mg: converts methemoglobin to cyanmethemoglobin
• Potassium dihydrogen phosphate (KH₂PO₄) - 140 mg: buffers solution
• Non-ionic detergent (e.g., Sterox): 1 mL: prevents turbidity from lipids/cells
• Distilled water: to make 1000 mL

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Image 8 — Bone Marrow Aspiration (BMA) Needle

A. Identify the instrument

B. Indications of its use

• Evaluation of unexplained cytopenias (anemia, thrombocytopenia, leukopenia)
• Diagnosis of leukemia, myeloma, lymphoma
• Assessment of iron stores
• Staging of lymphoma and solid tumors
• Evaluation of fever of unknown origin (FUO) - for marrow culture
• Monitoring treatment response in hematological malignancies
• Diagnosis of storage disorders (Gaucher's, Niemann-Pick)
• Myelodysplastic syndromes

C. Name 2 other BMA needles

1. Jamshidi needle - used for both aspiration and trephine biopsy
2. Islam's needle
3. Klima's needle
4. Westerman-Jensen needle

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Image 9 — Urine Dipstick / Reagent Strip

A. Identify the instrument

B. Write its use

• Semi-quantitative urine analysis for: glucose, protein, blood, leukocytes, nitrites, ketones, bilirubin, urobilinogen, pH, specific gravity, creatinine

C. Name and composition of reagent used

• Bromocresol Green or Tetrabromophenol blue (TBPB) buffered at pH 3.0
• The protein-error-of-indicators principle: the indicator changes color from yellow to blue-green in the presence of protein

D. What is microalbuminuria?

• Normal albumin excretion: < 30 mg/day (< 20 μg/min)
• Microalbuminuria: 30-300 mg/day (20-200 μg/min) or 30-300 mg/g creatinine
• Macroalbuminuria (clinical proteinuria): > 300 mg/day

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Image 10 — ESR Tube / Westergren Tube

A. Identify the instrument

B. Its uses

• Non-specific marker of inflammation
• Monitoring disease activity in inflammatory conditions (RA, SLE, TB, polymyalgia rheumatica)
• Screening/monitoring infections, malignancies, connective tissue disorders

C. Normal values

• Males: 0-15 mm/hour (Westergren) or 0-10 mm/hour (Wintrobe)
• Females: 0-20 mm/hour (Westergren) or 0-15 mm/hour (Wintrobe)
• Children: 0-10 mm/hour
• Elderly: up to 30-40 mm/hour may be acceptable

D. Causes of increased ESR

• Infections (TB, bacterial endocarditis)
• Inflammatory diseases (RA, SLE, vasculitis)
• Malignancies (especially myeloma - due to increased paraproteins)
• Anemia
• Hyperfibrinogenemia
• Increased immunoglobulins
• Renal failure, nephrotic syndrome
• Tissue necrosis (MI, stroke)

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Image 11 — Trephine Biopsy Needle / Jamshidi Needle

A. Identify the instrument

B. Indication of its uses

• When aspiration is a "dry tap" (aplastic anemia, myelofibrosis, hairy cell leukemia)
• Staging lymphoma
• Diagnosis of myelofibrosis
• Metastatic infiltration assessment
• Granulomatous diseases (sarcoidosis, TB)
• Assessment of cellularity (aplasia vs. hypercellularity)

C. Most common site

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Image 12 — Hemocytometer (Neubauer Chamber)

A. Identify the instrument

B. Its uses

• Manual cell counting: RBCs, WBCs, platelets, reticulocytes
• CSF cell counting
• Semen analysis (sperm count)
• Counting cells in body fluids
• Microorganism counting

C. Difference between old and modified version

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Image 13 — Wintrobe Tube + Westergren Tube (Comparison)

A. Name the first instrument and its use

1. Wintrobe ESR method
2. Packed Cell Volume (PCV/Hematocrit) measurement

B. What is the second instrument and why is it used?

• Longer tube (30 cm, graduated 0-200 mm) vs Wintrobe (11 cm)
• More accurate for elevated ESR values (doesn't reach the limit as quickly)
• International reference method (ICSH recommended)
• Less affected by anemia
• More sensitive for detecting mild elevations

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Image 14 — Blood Grouping Tile / Slide Agglutination

A. Interpret the blood group and identify the method

• Anti-A + Anti-B + Anti-H used
• Agglutination with Anti-A only → Blood Group A
• Agglutination with Anti-B only → Blood Group B
• Agglutination with both → Blood Group AB
• No agglutination with Anti-A or Anti-B → Blood Group O

B. What is Bombay blood group (O_h)?

• Rare blood group where individuals lack H antigen on RBC surface (due to homozygous mutation in FUT1 gene - h/h)
• Cannot express A, B, or O antigens (which are built on H antigen)
• Has anti-H, anti-A, anti-B antibodies in serum - dangerously reactive
• Appears as Group O on routine testing but is actually different
• Can only receive blood from other Bombay group donors
• First discovered in Bombay (Mumbai), India in 1952 by Bhende et al.
• Incidence: 1 in 10,000 in India; 1 in 1,000,000 globally

C. Advantages of tile/slide method

• Rapid (results in 2-3 minutes)
• Simple and inexpensive
• No special equipment needed
• Good for emergency situations
• Easy to learn

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Image 15 — Coagulometer / Semi-automated Coagulation Analyzer

A. Identify the instrument and write its 2 uses

1. Prothrombin Time (PT) / INR measurement
2. Activated Partial Thromboplastin Time (APTT) measurement
3. Also: fibrinogen, thrombin time, factor assays

B. What is clot retraction study?

• Clot retraction is the ability of a blood clot to retract (shrink/squeeze out serum), dependent on platelet function (platelet contractile protein - thrombosthenin/actomyosin) and fibrin.
• Method: Blood collected in a glass tube, clot forms, observed at 1 hour and 24 hours
• Normal: Clot retracts to ~50% of original volume within 1 hour; completes in 24 hours
• Abnormal (poor retraction): Thrombocytopenia, Glanzmann's thrombasthenia, fibrinolysis, polycythemia vera

C. Prolonged PT + Normal APTT - possibilities

• Factor VII deficiency (isolated - most common cause)
• Warfarin therapy (early - affects Factor VII first as it has shortest half-life)
• Liver disease (early/mild - Factor VII is made in liver)
• Vitamin K deficiency (early stage)
• Inherited Factor VII deficiency

D. Prolonged PT + Prolonged APTT - possibilities

• Deficiency of common pathway factors: X, V, II (prothrombin), or fibrinogen
• Severe liver disease (affects all clotting factors except vWF and VIII)
• DIC (Disseminated Intravascular Coagulation) - consumes all factors
• Vitamin K deficiency (severe - affects II, VII, IX, X)
• Warfarin overdose - affects II, VII, IX, X
• Heparin (therapeutic doses affect APTT more, but large doses affect both)

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Image 16 — Hemocytometer with WBC Pipette

A. Electronic method for counting WBC

• RBCs are lysed using a lysing agent
• WBCs pass through an aperture between two electrodes in an electrolyte solution
• Each cell displaces electrolyte, causing a brief electrical resistance change (voltage pulse)
• Pulse amplitude = cell volume; number of pulses = cell count
• Light scattering (in 5-part analyzers) further differentiates subtypes

B. Electronic method for counting platelets - advantageous or disadvantageous?

• Fast, automated
• Counts large numbers (more statistically accurate)
• Can calculate platelet indices (MPV, PDW, PCT)

• May falsely count: large platelets as RBCs, small RBCs/fragments as platelets
• Platelet clumps cause falsely low counts
• Giant platelets (Bernard-Soulier) may be missed
• Microparticles can cause spurious counts
• EDTA-induced platelet clumping (EDTA-dependent pseudothrombocytopenia)

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Image 17 — Westergren ESR Tube (measuring tube)

A. Identify the instrument and write length and diameter

• Length: 300 mm (30 cm)
• Internal diameter: 2.5 mm (±0.5 mm)
• Graduated from 0 at the top to 200 mm at the bottom

B. Other instrument that can be used and why Westergren is preferred

• Longer column - accommodates high ESR values without "ceiling effect"
• ICSH (International Committee for Standardization in Haematology) reference method
• More accurate and reproducible
• Less influenced by anemia
• Better sensitivity for high ESR values

C. Enumerate causes of increased and decreased ESR

• Infections (TB, endocarditis, osteomyelitis)
• Autoimmune diseases (RA, SLE, vasculitis)
• Multiple myeloma (marked elevation - due to paraproteins)
• Malignancies
• Anemia (decreased RBC mass)
• Pregnancy
• Hyperfibrinogenemia

• Polycythemia vera (increased RBC mass)
• Sickle cell anemia (altered RBC shape)
• Hereditary spherocytosis
• Hypofibrinogenemia / afibrinogenemia
• Congestive cardiac failure
• Cachexia

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Image 18 — Automated Hematology Analyzer (different model)

A. What is the machine?

B. What are the 3 qualitative methods (for Hb)?

1. Sahli's method (acid hematin) - visual comparison
2. Tallqvist method - color comparison with standard chart
3. Dare's method (oxyhaemoglobin) - visual colorimetry

C. Red cell indices

1. MCV (Mean Corpuscular Volume) - Normal: 80-100 fL
2. MCH (Mean Corpuscular Hemoglobin) - Normal: 27-32 pg
3. MCHC (Mean Corpuscular Hemoglobin Concentration) - Normal: 32-36 g/dL
4. RDW (Red Cell Distribution Width) - Normal: 11.5-14.5%
5. PCV/Hematocrit - Males: 40-54%, Females: 37-47%

• MCV = (PCV × 10) / RBC count (millions/μL) fL
• MCH = (Hb × 10) / RBC count pg
• MCHC = (Hb × 100) / PCV g/dL

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Image 19 — Tissue Processor / Microtome

A. Identify the instrument

B. Role of clearing agent

• Removes absolute alcohol
• Renders tissue transparent
• Prepares tissue for paraffin infiltration
• Xylene is most commonly used - clear, efficient, relatively safe

C. What is frozen section?

• Rapid intraoperative histopathology technique where fresh (unfixed) tissue is rapidly frozen (using cryostat/isopentane in liquid nitrogen) and sectioned at -20°C to -30°C
• Provides histological diagnosis within 10-15 minutes during surgery
• Cryostat is used to cut sections (4-8 μm)
• Uses:
  • Intraoperative diagnosis to guide extent of surgery
  • Assess tumor margins (whether margins are clear)
  • Lymph node assessment
  • Metabolic diseases (for enzyme histochemistry - as enzymes are preserved)
• Limitations: Not as good quality as paraffin sections; artifacts present; not suitable for fatty tissue, bone, or very small biopsies

D. What is decalcification?

• Process of removing calcium salts (calcium phosphate/hydroxyapatite) from calcified/bony tissue to make it soft enough to be sectioned.
• Performed after fixation but before routine processing.

1. Acid decalcification (fastest): Nitric acid 5-10%, Hydrochloric acid, Formic acid, Tri-chloro-acetic acid
2. Chelating agents (best morphology): EDTA (ethylene diamine tetra-acetic acid) - slow but excellent nuclear preservation
3. Ion exchange resins
4. Electrolytic method (rarely used)

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Image 20 — Blood Warmer / Water Bath

A. Identify the instrument and mention its 2 uses

1. Warming of blood/blood products before transfusion (to prevent hypothermia)
2. Incubation of samples for serological testing (e.g., Coombs test, crossmatch)
3. Dissolving cryoprecipitate or fresh frozen plasma

B. 2 features of blood transfusion reactions

1. Fever, chills, hypotension, flank/back pain
2. Hemoglobinuria (red/brown urine), jaundice

1. Rise in temperature ≥1°C during or within 4 hours of transfusion
2. No evidence of hemolysis; due to cytokines or recipient antibodies against donor leukocytes

1. Urticaria, pruritus, flushing
2. Anaphylaxis in severe cases (IgA deficiency)

1. Acute respiratory distress within 6 hours
2. Bilateral pulmonary infiltrates, hypoxia

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