Objective: To evaluate the predictive value of total serum bilirubin (TSB) < or =6 mg/dl at 24 +/- 6 hr postnatal age in identifying near term and term infants, who do not develop hyperbilirubinemia subsequently.
Design: Prospective study.
Setting: Tertiary care hospital.
Methods: All healthy neonates with gestation > or =35 weeks, in absence of significant illness or Rh hemolysis were included. TSB was estimated at 24 +/- 6 hr by micromethod using spectrophotometry. Infants were followed up clinically every 12 hr till discharge and then after 48 hr. TSB level was estimated again whenever clinical suspicion of jaundice exceeded 10 mg/dl. Primary outcome was defined as presence of hyperbilirubinemia (TSB > or= 17 mg/dl) till day five of age.
Results: Of the 220 infants, 213 (96.8%) were followed up. All infants were exclusively breastfed. Mean age at bilirubin estimation was 24.7 +/- 1.9 hr with mean TSB of 5.9 +/- 1.8 mg/dl. Clinically detectable jaundice was present in 164 (77%) and hyperbilirubinemia occurred in 22 (10.3%) infants. A TSB level of < or = 6 mg/dl at 24 +/- 6 hr was present in 136 (63.8%) infants and only one infant developed hyperbilirubinemia subsequently (probability < 1%). In the remaining 77 (36.1%) infants, with TSB >6 mg/dl, subsequent hyperbilirubinemia developed in 21 (27.2%) (sensitivity 95%, specificity 70.6%, positive predictive value 27.2%, negative predictive value 99.3%, likelihood ratio of positive test 3.23 and likelihood ratio of negative test 0.07). Babies with TSB levels higher than 6 mg/dl had a significant risk of developing hyperbilirubinemia (relative risk 38; 95% confidence interval 6-1675).
Conclusion: A TSB level of < or = 6 mg/dl at 24 +/- 6 hr of life predicted neonates who would not develop hyperbilirubinemia.