Prediction of hyperbilirubinemia in near-term and term infants

Objective. The purpose of this study was to determine whether end-tidal car bon monoxide (CO) corrected for ambient CO (ETCOc), as a single measurement or in combination with serum total bilirubin (STB) measurements, can predi ct the development of hyperbilirubinemia during the first 7 days of life. Methods. From 9 multinational clinical sites, 1370 neonates completed this cohort study from February 20, 1998, through February 22, 1999. Measurement s of both ETCOc and STB were performed at 30 +/- 6 hours of life; STB also was measured at 96 +/- 12 hours and subsequently following a flow diagram b ased on a table of hours of age-specific STB. An infant was defined as hype rbilirubinemic if the hours of age-specific STB was greater than or equal t o the 95th percentile as defined by the table at any time during the study. Results. A total of 120 (8.8%) of the enrolled infants became hyperbilirubi nemic. Mean STB in breastfed infants was 8.92 +/- 4.37 mg/dL at 96 hours ve rsus 7.63 +/- 3.58 mg/dL in those fed formula only. The mean ETCOc at 30 +/ - 6 hours for the total population was 1.48 +/- 0.49 ppm, whereas those of nonhyperbilirubinemic and hyperbilirubinemic infants were 1.45 +/- 0.47 ppm and 1.81 +/- 0.59 ppm, respectively. Seventy-six percent (92 of 120) of hy perbilirubinemic infants had ETCOc greater than the population mean. An ETC Oc greater than the population mean at 30 +/- 6 hours yielded a 13.0% posit ive predictive value (PPV) and a 95.8% negative predictive value (NPV) for STB greater than or equal to 95th percentile. When infants with STB >95th p ercentile at <36 hours of age were excluded, the STB at 30 +/- 6 hours yiel ded a 16.7% PPV and a 98.1% NPV for STB >75th percentile. The combination o f these 2 measurements at 30 +/- 6 hours (either ETCOc more than the popula tion mean or STB >75th percentile) had a 6.4% PPV with a 99.0% NPV. Conclusions. This prospective cohort study supports previous observations t hat measuring STB before discharge may provide some assistance in predictin g an infant's risk for developing hyperbilirubinemia. The addition of an ET COc measurement provides insight into the processes that contribute to the condition but does not materially improve the predictive ability of an hour s of age-specific STB in this study population. The combination of STB and ETCOc as early as 30 +/- 6 hours may identify infants with increased biliru bin production (eg, hemolysis) or decreased elimination (conjugation defect s) as well as infants who require early follow-up after discharge for jaund ice or other clinical problems such as late anemia. Depending on the incide nce of hyperbilirubinemia within an institution, the criteria for decision making should vary according to its unique population.