---

Liver Function Tests (LFTs) in Pediatric Practice

A Comprehensive MD/DNB Pediatrics Review

---

1. Definition and Limitations of LFTs

1. Metabolic/biosynthetic (proteins, lipids, carbohydrates)
2. Detoxification and biotransformation
3. Excretory (bile production/secretion)
4. Reticuloendothelial (Kupffer cell - heme metabolism)
5. Storage (glycogen, fat-soluble vitamins, iron)

• LFTs can be normal in advanced cirrhosis (>80% liver tissue must be destroyed before albumin/PT become abnormal)
• Enzymes (AST, ALT) reflect cell leakage, NOT function
• Many non-hepatic conditions elevate "liver enzymes" (muscle, bone, heart, hemolysis)
• Age-dependent normal ranges vary enormously - using adult reference intervals in children leads to systematic misclassification
• Intermethod variability between laboratories is substantial (especially ALP, bilirubin)

---

2. Physiology of the Liver and Rationale for Each Test

---

3. Components of the LFT Panel

3.1 Bilirubin

Heme (from RBC lysis) → Heme oxygenase in Kupffer cells → Biliverdin → Bilirubin reductase → Unconjugated (indirect) bilirubin → transported bound to albumin to hepatocyte → UDP-glucuronosyltransferase (UGT1A1) → Conjugated (direct) bilirubin → secreted into bile canaliculus → gut → urobilinogen

3.2 AST (Aspartate Aminotransferase / SGOT)

• Sources: Liver, cardiac muscle, skeletal muscle, kidney, brain, RBCs
• Location in hepatocyte: Cytoplasm AND mitochondria (less organ-specific)
• Half-life: 17 hours
• Normal (children, lab-dependent): ~10-40 IU/L

• Hepatocellular injury (hepatitis, toxic, ischemic)
• Myocardial infarction, myocarditis
• Skeletal muscle disease (myopathies, rhabdomyolysis)
• Hemolysis
• Vigorous exercise
• Hypothyroidism

3.3 ALT (Alanine Aminotransferase / SGPT)

• Sources: Primarily liver (more liver-specific than AST)
• Location: Cytoplasm only
• Half-life: 47 hours (longer persistence in blood than AST)
• Normal (children): ~10-35 IU/L

3.4 AST/ALT Ratio (De Ritis Ratio)

3.5 Alkaline Phosphatase (ALP)

• Sources: Liver (bile canaliculi), bone (osteoblasts), intestine, placenta, kidney
• Isoenzymes: Hepatic, bone, intestinal, placental
• Location: Canalicular surface of hepatocytes

• Infants (most active bone remodeling)
• Pubescent growth spurt (up to 400-700 IU/L can be normal)
• Quick Compendium of Clinical Pathology (p. 116): "Normal growth (in childhood) and pregnancy are causes of significant elevation in ALP. Separate reference intervals are required for children."

• GGT: If elevated with ALP → hepatic source; if normal → bone source
• 5'-nucleotidase: If elevated → hepatic origin confirmed
• ALP isoenzymes by electrophoresis

• Cholestasis (intrahepatic or extrahepatic)
• Biliary obstruction, biliary atresia, choledochal cyst
• Hepatic metastases (most sensitive liver enzyme for metastases - Quick Compendium, p. 132)
• Rickets, hyperparathyroidism, Paget disease

3.6 Gamma-Glutamyl Transferase (GGT)

• Sources: Biliary epithelial cells, hepatocytes (limiting plate), kidney, pancreas
• Primarily a biliary enzyme - not elevated in bone disease
• Normal (children): Neonate ~25-90 IU/L (higher); decreases to ~5-30 IU/L in older children/adults
• Half-life: 26 days (longest of all liver enzymes - persists long after insult)

• Confirms hepatic origin of elevated ALP (Quick Compendium, p. 150-155)
• Induced by drugs: phenytoin, phenobarbitone, valproate, carbamazepine, rifampicin, alcohol
• Highly sensitive marker for biliary involvement
• Marker of alcohol consumption in older patients

3.7 5'-Nucleotidase

• Source: Liver (biliary canalicular membranes), exclusively hepatic when compared to ALP
• Normal: 2-15 IU/L
• Clinical use: Confirms hepatic origin of elevated ALP (liver-specific)
• Elevated in cholestatic disease; NOT elevated in bone disease or pregnancy
• Advantage over GGT: Not induced by alcohol or medications

3.8 Serum Albumin

• Synthesis: Exclusively by hepatocytes (~12 g/day in adults)
• Half-life: 20 days (long half-life = insensitive marker of acute liver injury)
• Normal: 3.5-5.0 g/dL (slightly lower in infants: 2.5-3.5 g/dL in neonates)

• Decreased albumin indicates CHRONIC liver disease or severe malnutrition
• Causes of hypoalbuminemia: Liver failure (reduced synthesis), nephrotic syndrome (protein loss), protein-losing enteropathy, malnutrition, malabsorption, acute phase response (negative acute phase protein)
• Albumin is prognostic in chronic liver disease (component of Child-Pugh score)
• Albumin is NORMAL in acute hepatitis (because half-life 20 days; by the time liver recovers, albumin hasn't fallen yet)

3.9 Total Protein and Albumin/Globulin (A/G) Ratio

• Normal A/G ratio: 1.5:1 to 2.5:1
• Reversed A/G ratio (<1): Cirrhosis (low albumin + high immunoglobulins), multiple myeloma, autoimmune states
• In cirrhosis/liver failure: patients have LOW albumin but ELEVATED immunoglobulin (Henry's p. 3834)

3.10 Prothrombin Time (PT) and INR

• Rationale: Clotting factors II, V, VII, IX, X and fibrinogen are synthesized exclusively in the liver. Factor VII has the shortest half-life (4-6 hours), making PT the most sensitive synthetic function test in acute liver failure.
• Normal PT: 10-14 seconds; INR ~1.0
• PT prolongation in liver disease reflects failure of hepatocyte synthetic function
• Critical: Must rule out vitamin K deficiency (hemorrhagic disease of newborn, malabsorption) before attributing PT prolongation to liver failure - give IV vitamin K 1 mg/kg and re-check in 4-6 hours

• PT >15 seconds (INR >1.5) without encephalopathy requires vigilance
• PT >20 seconds (INR >2.0) = defining criterion for PALF with encephalopathy (PALF Study Group criteria)
• Factor V <30% = poor prognosis; used in Clichy criteria for LT referral

3.11 Serum Ammonia

• Source: Product of amino acid and nucleic acid catabolism; normally converted to urea by liver (Krebs-Henseleit urea cycle)
• Normal: <40 µmol/L (fasting); varies by lab
• Elevated when >80% of liver parenchyma is destroyed (Henry's p. 3800)
• Pre-analytical pitfalls (critical): Specimens must be chilled on ice, transported immediately, hemolysis minimized, tested within 15 minutes - ammonia rises ~20% per hour in stored samples; patients must not smoke for several hours before draw (Quick Compendium, p. 213-218)

• Acute liver failure (most common acquired)
• Urea cycle defects (neonates/infants - ASL, OTC deficiency, CPS deficiency)
• Organic acidemias (propionic, methylmalonic acidemia)
• Reye syndrome
• Severe constipation (increased ammonia production from gut bacteria)
• Valproate therapy (impairs urea cycle)
• Total parenteral nutrition

3.12 Serum Bile Acids

• Synthesis: Hepatocytes from cholesterol; undergo enterohepatic circulation
• Normal (fasting): <10 µmol/L
• Gold standard for cholestasis - rises earlier and more sensitively than bilirubin
• Elevated in intrahepatic cholestasis, biliary obstruction, cirrhosis
• Used in diagnosis of obstetric cholestasis, PFIC, bile acid synthesis defects
• In PFIC types 1 and 2: Very high bile acids + LOW/NORMAL GGT

3.13 Serum Lactate

• Elevated in acute liver failure (impaired hepatic lactate clearance), mitochondrial hepatopathies, Reye syndrome, urea cycle defects
• Persistent lactic acidosis in ALF carries poor prognosis (King's College Criteria)

---

4. Normal Reference Ranges - Age-Related Variations

• Neonatal GGT is physiologically very high (maternal transfer + immature biliary system) - can be 5-10x adult normal in first weeks
• Neonatal ALP is elevated due to placental + bone isoenzymes
• Conjugated bilirubin >1 mg/dL at any age in an infant is ALWAYS pathological (NASPGHAN/ESPGHAN recommendation for fractionating bilirubin in any jaundiced infant >2 weeks)
• Puberty: ALP may reach 700 IU/L physiologically (Tanner stage 3-4)

---

5. Classification of Liver Injury Based on LFT Patterns

The R-Ratio (DILI Network/CIOMS Classification)

R = (ALT/ULN) ÷ (ALP/ULN)

Pattern Recognition Summary

---

6. Detailed Parameter Interpretation

Isolated Hyperbilirubinemia

AST vs ALT - Key Differentiating Points

ALP vs GGT

---

7. Pattern-Based Interpretation with Differential Diagnosis

---

8. Stepwise Diagnostic Algorithm - Approach to Deranged LFTs in a Child

STEP 1: CONFIRM ABNORMALITY
- Repeat LFTs if mildly abnormal (exclude pre-analytical errors)
- Use age-appropriate reference ranges
- Check for hemolysis (false elevations of AST, bilirubin; false lowering of ALP)

STEP 2: CHARACTERIZE THE PATTERN
- Hepatocellular vs Cholestatic vs Mixed (R ratio)
- Acute vs Chronic (albumin, PT normal = acute; abnormal = chronic or severe acute)
- Is it conjugated or unconjugated hyperbilirubinemia?
- Are synthetic markers abnormal? (PT, albumin, factor V)

STEP 3: NON-HEPATIC CAUSES
- AST elevated alone → rule out muscle disease (CK, LDH)
- ALP elevated alone → rule out bone disease (GGT normal?)
- Unconjugated bili alone → rule out hemolysis (blood smear, reticulocyte count, Coombs)
- Gilbert syndrome (fasting/stress-induced, benign)

STEP 4: HISTORY & CLINICAL CONTEXT
- Age: Neonatal cholestasis vs. childhood hepatitis vs. adolescent NAFLD
- Drugs (valproate, isoniazid, methotrexate, paracetamol)
- Family history (Wilson disease, metabolic disorders)
- Viral prodrome, fever, travel, blood products
- Obesity/metabolic syndrome → MASLD
- Autoimmune disease, inflammatory bowel disease → AIH, PSC

STEP 5: TARGETED INVESTIGATIONS BY PATTERN

HEPATOCELLULAR PATTERN:
  → Viral markers: HAV IgM, HBsAg/anti-HBc IgM, anti-HCV, EBV/CMV PCR
  → Autoimmune: ANA, ASMA, anti-LKM1, IgG
  → Metabolic: serum ceruloplasmin, 24h urine copper (>6yr), slit-lamp exam
  → Drug history + paracetamol level
  → Thyroid function (hypothyroidism causes AST elevation)
  → Consider liver biopsy if cause unclear after 3-6 months

CHOLESTATIC PATTERN (Neonate/Infant):
  → URGENT: Direct Coombs, T&S, thyroid function, cultures
  → HIDA scan / hepatobiliary scintigraphy (biliary atresia if no excretion)
  → Abdominal ultrasound (choledochal cyst, gallstones)
  → Liver biopsy
  → Genetic/metabolic workup: alpha-1-antitrypsin (Pi typing), CFTR, inborn errors
  → Consider ERCP/MRCP

CHOLESTATIC PATTERN (Older child):
  → Ultrasound/MRCP for PSC, choledochal cyst
  → ANCA + IBD workup (PSC association)
  → pANCA for PSC

STEP 6: IDENTIFY ACUTE LIVER FAILURE EARLY
- Signs: PT/INR >2.0, encephalopathy, coagulopathy, rising bilirubin
- Immediate: Blood glucose, ammonia, factor V, complete coag screen
- Refer to tertiary center/liver transplant unit

---

9. LFT Patterns in Common Pediatric Diseases

9.1 Viral Hepatitis

9.2 Autoimmune Hepatitis (AIH)

• ALT/AST: Markedly elevated (can be 500-2000 IU/L)
• ALP: Moderately elevated or normal
• Bilirubin: Elevated conjugated
• Albumin: May be low (suggests chronicity)
• IgG: Elevated (>1.3x ULN - characteristic)
• Autoantibodies: Type 1 (ANA, ASMA): most common in older children; Type 2 (anti-LKM1): younger children
• Liver biopsy: Interface hepatitis ("piecemeal necrosis"), rosette formation, plasma cell infiltration

9.3 Wilson Disease

• ALT/AST: Elevated (mild to moderate in chronic; can be paradoxically low in acute fulminant Wilson disease)
• ALP: Characteristically LOW or LOW-NORMAL in Wilson disease presenting as acute liver failure (unique and exam-critical pearl)
• Bilirubin: ↑↑, often conjugated (Coombs-negative hemolytic anemia contributes)
• PT: Prolonged (synthetic failure)
• Ceruloplasmin: Low (<0.20 g/L) in most; can be normal in acute phase
• Kayser-Fleischer rings on slit-lamp
• 24-hour urine copper: >100 µg/day (>40 µg/day in children)
• Liver copper on biopsy: >250 µg/g dry weight

9.4 Biliary Atresia

• Conjugated hyperbilirubinemia (direct bili >1 mg/dL) from birth or first 2 weeks
• GGT: Markedly elevated (GGT >300 IU/L is highly suggestive of biliary atresia over other causes of neonatal cholestasis - GGT >200 IU/L with sensitivity >80%)
• ALP: Elevated
• Transaminases: Mildly to moderately elevated (100-300 IU/L)
• Bile acids: Very elevated
• Sleisenger & Fordtran (p. 3487): Must differentiate conjugated from unconjugated hyperbilirubinemia in neonates; liver/biliary disease must be considered in any neonate >2-3 weeks with persistent jaundice

9.5 Choledochal Cyst

• Conjugated hyperbilirubinemia
• ALP, GGT: ↑↑
• Transaminases: ↑ (if secondary hepatitis)
• Classic triad (Quervain): Jaundice + RUQ pain + palpable mass (seen in only 10-20%)
• Amylase: May be elevated (pancreatic juice reflux)
• Diagnosis: Ultrasound + MRCP

9.6 Drug-Induced Liver Injury (DILI) in Children

9.7 NAFLD/MASLD

• Most common cause of elevated liver enzymes in children and adolescents in developed countries (PMID 39574069 - systematic review 2024)
• ALT elevation (mildly to moderately): ALT often > AST (unlike alcoholic hepatitis)
• GGT: Mildly elevated
• ALP: Usually normal
• Bilirubin, albumin, PT: Normal until advanced cirrhosis
• AST:ALT ratio <1 typical
• Diagnosis requires imaging (ultrasound: bright liver) + exclusion of other causes + ideally biopsy for staging

9.8 Acute Liver Failure (ALF/PALF)

• Massive transaminase elevation: AST/ALT >10,000 IU/L frequently (Henry's p. 3823)
• AST disproportionately exceeds ALT (mitochondrial release)
• Bilirubin: ↑↑↑ (conjugated)
• ALP: Elevated (except Wilson disease where low)
• Albumin: Low
• PT: Markedly prolonged (INR >2.0 is a PALF defining criterion)
• Ammonia: ↑↑↑ (hepatic encephalopathy)
• Lactate: Elevated (poor prognostic sign)
• Glucose: Hypoglycemia (failure of gluconeogenesis)

• Neonates: HSV, EBV, CMV, HHV6, neonatal hemochromatosis, gestational alloimmune liver disease, mitochondrial hepatopathy, galactosemia
• Infants: Metabolic (Wilson excluded), viral, tyrosinemia
• Children/Adolescents: Viral (HAV, HBV), Wilson disease, AIH, DILI (paracetamol), indeterminate (~50%)

9.9 Sepsis

• Multifactorial: Cholestatic pattern predominates (endotoxin inhibits bile salt transporters)
• Conjugated bilirubin ↑↑
• ALP + GGT: ↑
• Transaminases: ↑ (moderate; ischemic hepatitis component if hypoperfused)
• PT: ↑ (DIC component + hepatic synthetic failure)
• "Neonatal sepsis" is the most important differential of neonatal conjugated hyperbilirubinemia and must be actively excluded (cultures, CRP, CBC)

9.10 Dengue

• Hepatocellular pattern: ALT/AST elevation in 60-80% of cases
• AST typically exceeds ALT (mitochondrial injury; also released from muscle and platelets)
• Bilirubin: Mild conjugated elevation
• PT: May be prolonged (dengue-associated coagulopathy)
• Platelet count: Severely decreased (thrombocytopenia cardinal feature)
• LFT elevation correlates with dengue severity (severe dengue = higher transaminases)
• Rarely, dengue hepatitis can progress to ALF

9.11 Typhoid

• Mild hepatocellular pattern: ALT/AST elevation (2-3x ULN) in ~40-50% of cases
• Hepatosplenomegaly present clinically
• ALP: Mildly elevated
• Bilirubin: Mildly elevated (often unconjugated component due to hemolysis)
• Rarely, "typhoid hepatitis" with marked transaminase elevation (>5x) - distinguishing from viral hepatitis requires blood/stool cultures, Widal test

9.12 EBV and CMV Infections

9.13 Hemolytic Disorders

• Unconjugated hyperbilirubinemia predominantly
• AST: Mildly elevated (from RBC lysis - RBCs contain AST)
• ALT: Minimal or no elevation
• ALP: Normal
• Haptoglobin: Low
• Urine urobilinogen: Elevated
• Stool color: Dark (increased stercobilinogen)
• LDH: Elevated
• Reticulocyte count: Elevated
• Blood smear: Microspherocytes (hereditary spherocytosis, ABO incompatibility), sickle cells, fragmented cells (microangiopathic)

9.14 Muscle Diseases (Isolated AST Elevation)

• AST elevated, ALT normal or minimally elevated
• CK (creatine kinase): Markedly elevated
• LDH: Elevated
• Causes: Myopathies, rhabdomyolysis, myositis, hypothyroidism (muscle + liver AST), intense exercise, trauma
• Pediatric conditions: Duchenne/Becker muscular dystrophy (AST/ALT both elevated but CK >> ALT distinguishes), myositis, dermatomyositis

9.15 Bone Disorders (ALP Elevation)

• ALP elevated, GGT normal, 5'-nucleotidase normal
• Conditions: Rickets (nutritional/vitamin D deficiency - most common in India), hyperparathyroidism, healing fractures, Paget disease, metastatic bone disease, normal pubescent growth
• Bone-specific ALP isoenzyme can be quantified for confirmation

---

10. Synthetic Function of the Liver and Prognostic Markers

• Class A (5-6): Good function; B (7-9): Moderate; C (10-15): Poor - transplant candidate

PELD = 4.36 × (Age <1) - 1.87 × ln[albumin g/dL] + 38.56 × ln[INR] + 10.48 × ln[total bili mg/dL] + 6.67 × (growth failure flag)

---

11. Dynamic Liver Function Tests

---

12. Common Isolated Abnormality Patterns

Isolated Unconjugated Hyperbilirubinemia

• Gilbert syndrome (most common benign cause; autosomal recessive UGT1A1 promoter variant)
• Right heart failure / hemolysis / hematoma resorption
• Crigler-Najjar type I (absent UGT1A1, severe) and type II (reduced, responds to phenobarbitone)
• Congenital hypothyroidism, Drugs (rifampicin, probenecid)

Isolated Conjugated Hyperbilirubinemia

• Dubin-Johnson syndrome (black pigment on liver biopsy; urine coproporphyrin pattern altered)
• Rotor syndrome (no black pigment; elevated total urine coproporphyrin)
• Neonatal: Biliary atresia, CMV, rubella, galactosemia, alpha-1-antitrypsin deficiency, etc. (see Table 62.1 - Sleisenger & Fordtran)

Isolated ALT Elevation

• Most common cause in children: MASLD/NAFLD (especially with obesity)
• Others: Chronic HBV carrier (mild elevation), alpha-1-antitrypsin heterozygosity, celiac disease (PMID 36619153), thyroid disease, drug effect
• Algorithm: Rule out viral hepatitis (HBsAg, anti-HCV), Wilson disease (>6 yr), autoimmune hepatitis (ANA, ASMA, IgG), metabolic liver disease

Isolated AST Elevation

• Always consider muscle disease first (CK level)
• Hemolysis (check blood smear)
• Thyroid disease (hypothyroidism causes both CK and AST elevation)
• Vigorous exercise

Isolated ALP Elevation

• In children: Normal growth/pubescent growth spurt (confirm by checking GGT)
• Bone disease (rickets, Paget, healing fractures)
• Only concern if GGT also elevated → hepatobiliary cause
• Rare: Familial hypophosphatasemia (paradoxically low ALP)

Isolated GGT Elevation

• Drug induction (phenytoin, phenobarbitone, carbamazepine, rifampicin)
• Alcohol (in adolescents)
• Fatty liver (early MASLD)
• Early cholestatic disease

Hypoalbuminemia

• Chronic liver disease / Cirrhosis
• Loss (nephrotic syndrome, protein-losing enteropathy, burns)
• Inflammation (acute phase response - albumin is negative acute phase protein)
• Inadequate synthesis (malnutrition, malabsorption)
• Malabsorption (celiac, IBD)

---

13. Clinical Case Scenarios

Case 1: 4-week-old infant, jaundiced since day 5, stools pale, urine dark

• Total bilirubin: 9.2 mg/dL; Direct: 5.8 mg/dL (63% of total)
• ALT: 150, AST: 130, GGT: 450 IU/L, ALP: 480 IU/L
• Albumin: 3.2 g/dL, PT: 16 sec

Case 2: 12-year-old boy, obesity, found to have ALT 78, AST 55, ALP 210, GGT 42 on routine testing

• Bilirubin normal, albumin normal, PT normal

Case 3: 16-year-old girl, 6 months of fatigue, jaundice, ALT 1200, AST 890, ALP 180, GGT 95, bilirubin 4.2 mg/dL, IgG 2800 mg/dL, ANA 1:160

• Albumin 2.9, PT prolonged to 18 sec

Case 4: 14-year-old boy, acute jaundice + hemolytic anemia, Coombs negative, ALT 200, AST 180, ALP 40 (LOW), GGT 22, bilirubin 8.5 mg/dL, PT 22 sec, neuropsychiatric changes, Kayser-Fleischer rings on slit-lamp

• Ceruloplasmin: 0.08 g/L (very low), urine copper: 280 µg/24h

Case 5: Premature neonate (32 weeks), day 3, total bilirubin 13 mg/dL, direct 0.4 mg/dL

---

14. Recent Updates and Guideline Recommendations

• MASLD nomenclature change (2023): Delphi consensus renamed NAFLD to MASLD (Metabolic dysfunction-Associated Steatotic Liver Disease) and NASH to MASH. Cardiometabolic criteria must be present. A 2024 systematic review with meta-analysis (PMID 39574069) confirmed that lifestyle interventions (Mediterranean diet - PMID 39363272) improve LFTs and steatosis in pediatric MASLD.
• NASPGHAN/ESPGHAN 2023 Guidance on Neonatal Cholestasis: Any infant with jaundice beyond 2 weeks of age should have total AND direct bilirubin measured. Fractionated bilirubin >1 mg/dL (or >20% total) triggers urgent workup.
• PALF (Pediatric Acute Liver Failure) Study Group Updates: Etiology remains indeterminate in ~50% of cases; indeterminate ALF has better prognosis than previously thought; seronegative AIH is now recognized as a distinct entity.
• Wilson Disease (EASL 2022): Liver copper >250 µg/g dry weight + 2 Kayser-Fleischer rings = diagnosis confirmed. Leipzig score ≥4 = diagnosis highly likely.
• ESPGHAN PFIC Guidelines (2021-2023): Recognize PFIC types 1-6 (ATP8B1, ABCB11, ABCB4, TJP2, NR1H4, MYO5B). GGT-LOW PFIC (types 1 and 2) vs GGT-HIGH PFIC (types 3+). Surgical biliary diversion and ileal bile acid transporter (IBAT) inhibitors (odevixibat, maralixibat) are new treatment options.
• AASLD 2023 on Autoimmune Hepatitis: Simplified AIH score validated in pediatrics; long-term immunosuppression required in most children; flares common at puberty.
• DILI Network (DILIN) Criteria: R-ratio remains the standard for classification of drug-induced liver injury pattern.

---

15. High-Yield Tables

Table A: Hepatocellular vs Cholestatic Injury

Table B: Conjugated vs Unconjugated Hyperbilirubinemia

Table C: AST vs ALT

Table D: ALP vs GGT

Table E: Acute vs Chronic Liver Disease

---

16. Mnemonics and Memory Aids

• Biliary atresia / Bacterial sepsis
• Inborn errors of metabolism (galactosemia, tyrosinemia, alpha-1-antitrypsin)
• Liver disease (CMV, rubella, HSV, toxoplasma - TORCH)
• Endocrine (hypothyroidism, panhypopituitarism)

• Wow hemolysis (hemolytic disease of newborn, spherocytosis, G6PD)
• Hepatic uptake defect (Gilbert, drugs)
• Absent/reduced conjugation (Crigler-Najjar)
• More production (large hematoma, polycythemia)

• Puberty growth spurt (physiological)
• ALP from bone (rickets, fractures, Paget)
• Regan isoenzyme (malignancy)
• Real liver disease (cholestasis)
• Obstruction (biliary atresia, choledochal cyst)
• Transient hyperphosphatasemia of infancy (benign, self-limiting)

• "In alcohol, AST > ALT because AST comes from Two places (cytoplasm + mitochondria) - mitochondria are damaged by alcohol"
• If AST:ALT > 2:1 → think Alcohol or Acute liver failure / cirrhosis

• Ship on ice
• Minimize hemolysis
• Analyze at bedside immediately
• Refrain from smoking (patient)
• Time matters (rises 20% in first hour)

---

17. MD/DNB Examination Questions

5-Mark Questions (Short Answers)

1. "Discuss the interpretation of an elevated serum alkaline phosphatase in a 10-year-old child." - Emphasize physiological elevation, GGT as differentiator, ALP isoenzymes, bone vs hepatic causes, LOW ALP in Wilson disease.
2. "What is the R-ratio? How does it help classify liver injury?" - Formula, hepatocellular/cholestatic/mixed pattern, DILI application.
3. "Enumerate the tests of synthetic function of the liver and their clinical significance." - Albumin (chronic), PT/INR (acute + chronic), factor V, fibrinogen, PELD score.
4. "What is the significance of serum GGT in pediatric hepatology?" - Biliary marker, drug induction, confirms hepatic ALP, LOW GGT in PFIC 1 and 2, HIGH GGT in biliary atresia.
5. "Discuss the pre-analytical factors affecting serum ammonia measurement." - Chilling, hemolysis, immediate processing, smoking restriction, 20% rise per hour.

10-Mark Questions (Long Answers)

1. "Discuss the approach to a neonate presenting with jaundice at 4 weeks of age. How will LFTs guide your diagnosis and management?" - Emphasize fractionation, conjugated vs unconjugated, biliary atresia (urgency of Kasai < 60-90 days), GGT role, HIDA scan, metabolic workup (galactosemia, A1AT, thyroid, cultures for sepsis).
2. "A 14-year-old presents with acute liver failure. Discuss the LFT patterns, prognostic markers, and management priorities." - PALF criteria, PT/INR, factor V, ammonia, Glasgow Coma Scale, King's College Criteria, Wilson disease (low ALP), DILI history, viral serology, transplant referral.
3. "Describe the classification of liver injury based on LFT patterns. Discuss the LFT findings in viral hepatitis, autoimmune hepatitis, Wilson disease, and biliary atresia." - Complete R-ratio framework + individual disease patterns as tabulated above.
4. "Discuss the role of LFTs in monitoring drug-induced liver injury (DILI) in children. Which drugs commonly cause liver injury in pediatrics and what is their LFT pattern?" - Valproate (hyp-ammonemia pattern), paracetamol (zone 3 centrilobular necrosis), isoniazid, methotrexate, L-asparaginase. R-ratio classification for each.
5. "Describe the synthetic function of the liver and the clinical utility of albumin, prothrombin time, factor V, and serum ammonia in managing a child with decompensated liver disease." - Half-lives, Child-Pugh, PELD, Clichy criteria, hepatic encephalopathy grading.

Viva Questions

1. What is the De Ritis ratio? When is it >2:1 and what does it suggest? AST:ALT ratio; >2:1 in alcoholic hepatitis (even in adolescents), cirrhosis, acute liver failure; mitochondrial AST release.
2. Why is alkaline phosphatase low in Wilson disease? Copper competes with zinc (cofactor for ALP); also hemolysis reduces zinc availability and destroys ALP enzyme. Low ALP in the context of ALF and hemolysis = Wilson disease pearl.
3. What is the difference between PFIC type 1-2 vs PFIC type 3 on LFTs? Types 1 and 2 - LOW/NORMAL GGT despite severe cholestasis; Type 3 (MDR3 mutation) - HIGH GGT.
4. Why is albumin normal in acute hepatitis but low in cirrhosis? Half-life of albumin = 20 days; acute hepatitis resolves before albumin falls appreciably; only when >80% parenchyma is destroyed chronically does albumin fall.
5. What is the significance of a prolonged PT that corrects with IV vitamin K in a child? Suggests vitamin K deficiency (cholestasis causing fat-soluble vitamin malabsorption, or hemorrhagic disease of newborn) rather than true hepatic synthetic failure.
6. Enumerate causes of Coombs-negative hemolytic anemia with liver disease. Wilson disease (most important in pediatrics), pyruvate kinase deficiency, G6PD deficiency with hepatitis.
7. What is transient hyperphosphatasemia of infancy? Benign self-limiting condition in children <5 years; ALP elevated to 10-50x ULN with normal GGT, no bone/liver disease; spontaneously normalizes within months; requires no treatment.
8. What are the King's College Criteria for LT in ALF? For non-paracetamol ALF: INR >6.5, or 3 of [age <10 or >40; non-A non-B hepatitis or drug reaction; jaundice-to-encephalopathy interval >7d; bilirubin >17.4 mg/dL; INR >3.5].

---

18. Key Take-Home Messages and Exam Pearls

1. LFTs are markers of injury, NOT function - only albumin, PT/INR, factor V, and ammonia reflect true hepatic synthetic/metabolic function.
2. Conjugated bilirubin >1 mg/dL in any infant is ALWAYS pathological - must rule out biliary atresia urgently (Kasai before 60-90 days is critical).
3. ALP is physiologically elevated in growing children - always check GGT to confirm hepatic vs bone origin; GGT normal = bone origin; GGT elevated = hepatic/biliary cause.
4. LOW ALP + acute liver failure + Coombs-negative hemolytic anemia = Wilson disease until proven otherwise.
5. LOW GGT + severe cholestasis = PFIC type 1 or 2 (ATP8B1 or ABCB11 mutations).
6. AST:ALT ratio <1 (ALT predominant) = viral hepatitis, MASLD, AIH; >2:1 = alcoholic, cirrhosis, ALF, mitochondrial disease.
7. Albumin has a 20-day half-life - normal in acute liver disease; low only in chronic disease (>80% parenchymal loss) or protein-losing states.
8. Serum ammonia is critically pre-analytically sensitive - must be chilled on ice, processed immediately; rises 20% per hour.
9. PT/Factor V are the most sensitive prognostic markers in ALF - factor V <30% = indication for liver transplant referral (Clichy criteria).
10. Neonatal GGT is physiologically very high (5-10x adult ULN) in first weeks of life - adult GGT reference ranges cannot be applied.
11. R-ratio classifies DILI: ≥5 = hepatocellular; ≤2 = cholestatic; 2-5 = mixed.
12. MASLD (formerly NAFLD) is now the most common cause of elevated liver enzymes in children/adolescents in developed countries - always consider in obese children with mild ALT elevation.
13. Dengue hepatitis: AST often exceeds ALT due to muscle/platelet involvement, not just liver injury.
14. Valproate hepatotoxicity is most dangerous in children <2 years on polytherapy - presents with hyperammonemia + hepatocellular injury + metabolic acidosis; potentially fatal mitochondrial injury.
15. Gilbert syndrome is the commonest cause of benign unconjugated hyperbilirubinemia in adolescents - fasting, illness, or dehydration triggers jaundice; no treatment required; exam-frequently tested.

---