Total Serum Bilirubin in Paediatrics

Also written as Total Bilirubin.

Total serum bilirubin measures the overall bilirubin load in a child’s blood. It helps distinguish physiologic jaundice from pathologic causes, guides phototherapy, and flags severe hyperbilirubinaemia that may lead to kernicterus.

Definition and diagnosis

Total serum bilirubin (TSB) is the sum of unconjugated and conjugated bilirubin in plasma. It is measured by a diazo or enzymatic assay and expressed in µmol/L or mg/dL.

• TSB: Normal, physiologic, or pathologic elevation
• Direct (conjugated) bilirubin: >15% of TSB or >2 mg/dL indicates conjugated hyperbilirubinaemia

• TSB < 20 µmol/L (0.3 mg/dL) is normal in a newborn after 24 h

Severity and staging

The Bhutani nomogram guides phototherapy thresholds in term infants. In low‑resource settings, a simplified 2‑hour rise of >10 µmol/L or a TSB >200 µmol/L warrants urgent review.

• TSB >500 µmol/L: emergency exchange transfusion

Causes, most likely first

In East Africa, the top causes of hyperbilirubinaemia are haemolysis, infection, and liver immaturity. Consider local endemic diseases and herbal remedies.

• Congenital liver disease – biliary atresia, neonatal hepatitis

How it presents

Jaundice appears as yellow discoloration of sclera, skin, and mucosa. In severe cases, the infant may be lethargic, have poor feeding, or display seizures.

• Kernicterus – tremor, opisthotonus, or seizures

Investigations

Use the table to decide which test answers which clinical question. If a test is unavailable, use clinical judgment and basic labs.

• Peripheral blood smear: Polychromasia, spherocytes, or schistocytes
• Coombs test: Positive direct Coombs indicates alloimmune hemolysis
• Blood culture: Positive culture confirms bacterial sepsis
• Liver function tests (AST, ALT, GGT): Elevated transaminases suggest hepatitis or drug toxicity
• Ultrasound abdomen: Dilated ducts or gallbladder wall thickening
• Hemoglobin electrophoresis: HbS >50% indicates sickle cell

Red flags and complications

Rapid rise, conjugated hyperbilirubinaemia, or neurological signs require immediate action. Kernicterus is irreversible and fatal if untreated.

• Seizures, poor feeding, or lethargy

Management

Treat the underlying cause first. Supportive care includes phototherapy, hydration, and monitoring. Avoid drugs that increase bilirubin or cause hepatotoxicity.

• Avoid hepatotoxic drugs – e.g., paracetamol overdose

Follow-up and prevention

Re‑check TSB after 6–24 h if risk factors are present. Educate caregivers on feeding, sun exposure, and avoiding herbal remedies.

• Avoid herbal teas in neonates

Often confused with

Physiologic jaundice, neonatal hepatitis, and hemolytic disease of the newborn can mimic each other. Use direct bilirubin and Coombs to differentiate.

• Hemolytic disease – unconjugated, with anemia and reticulocytosis

Where results can mislead

Low albumin can falsely lower TSB. Hemolysis during sampling can raise unconjugated bilirubin. Inadequate calibration of photometers can misread TSB.

• Confirm with repeat test if results are unexpected

Questions an examiner may ask

• A 3‑day‑old term infant has TSB 280 µmol/L and is feeding well. What is the next step? — Initiate phototherapy; monitor TSB every 6–12 h.
• A 2‑day‑old infant has TSB 350 µmol/L and a rising trend of 12 µmol/L in 2 h. What is the urgent intervention? — Exchange transfusion.
• Why is a direct Coombs test performed in a jaundiced newborn? — To detect alloimmune haemolysis; a positive result changes management.
• A newborn has conjugated bilirubin 30% of TSB. What is the most likely diagnosis? — Neonatal hepatitis or biliary atresia; further imaging needed.
• Which drug should be avoided in a neonate with hyperbilirubinaemia? — Paracetamol in high doses, as it can worsen hepatic injury.
• A 4‑month‑old child presents with jaundice and a history of malaria treatment. What is the most likely cause? — Hemolysis from antimalarial drugs or malaria‑induced hemolysis.

When to seek help

• Severe hyperbilirubinaemia (TSB >300 µmol/L), rapid rise, conjugated hyperbilirubinaemia, seizures, lethargy, poor feeding

Quick questions

What is the normal TSB range in a term newborn after 24 h?

Under 20 µmol/L (0.3 mg/dL) is normal.

When is phototherapy indicated in a term infant?

When TSB exceeds the Bhutani nomogram thresholds for age and weight.

Why is a direct Coombs test important?

It identifies immune haemolysis, guiding treatment and monitoring.