Evaluation of Transcutaneous Bilirubinometry (TcB) in the First Hours of Life to Predict Subsequent Invasive Bilirubin Testing during the Birth Hospitalization

BACKGROUND: TcB is well-established for non-invasive bedside monitoring of trends in neonatal bilirubin values. It is not known whether an ETcB value will assist in (a) predicting subsequent TcB values, or (b) the need for evaluation of, or treatment for, hyperbilirubinemia. PURPOSE: To determine whether an ETcB value alone - or used to calculate a rate of rise (ROR) in TcB - will identify those neonates who are at higher risk for subsequent jaundice and/or a higher likelihood of needing phototherapy (PHT). METHODS: ETcB values were obtained within 6h of delivery from a convenience sample of neonates admitted to the Parkland Newborn Nursery. ROR was calculated as the average hourly increase between ETcB and subsequent TcB obtained at 18-36h of age. The predictive values relating (a) ETcB alone and/or ROR to subsequent TcB values, and (b) need for PHT, were determined. RESULTS: 516 study neonates had a mean birth weight of 3401±468 grams and gestational age of 39±1.4 weeks; 83% were Hispanic, and 53% were male. Correlations between ETcB and TcB values at 24h, 36h, and 48h were r=0.31, 0.40, and 0.32 respectively (all p values <0.001). Predictive indices are shown: TcB >95 %ile at 42-66 hours* Sens Spec PPV NPV pΨ ETcB¥ 0.80 0.87 0.50 0.16 0.97 0.0007 0.90 0.78 0.57 0.16 0.96 0.002 ROR§ 0.11 1.00 0.13 0.11 1.00 0.09 0.18 0.83 0.48 0.15 0.96 0.007 0.25 0.52 0.88 0.31 0.95 0.00003 As shown above for the 95th %ile, and using ETcB or ROR as the predictor cutoff for subsequent TcB, the NPV was always ≥0.95. For neonates with ROR ≥0.25, 79% had TcB >75th %ile at 42-66h (vs 32% with ROR <0.25; p<0.001). Median ETcB was 2-fold higher in those neonates who were subsequently treated with PHT (p=0.002), and ROR was ≥0.30 mg/dL in 63% of these neonates. DISCUSSION: These results suggest that ETcB may provide a useful baseline and have clinical utility primarily in identifying those neonates at low risk of subsequent hyperbilirubinemia.