Discrepancies between transcutaneous and serum bilirubin measurements.

OBJECTIVE To characterize discrepancies between transcutaneous bilirubin (TcB) measurements and total serum bilirubin (TSB) levels among newborns receiving care at multiple nursery sites across the United States. METHODS Medical records were reviewed to obtain data on all TcB measurements collected during two 2-week periods on neonates admitted to participating newborn nurseries. Data on TSB levels obtained within 2 hours of a TcB measurement were also abstracted. TcB--TSB differences and correlations between the values were determined. Data on demographic information for individual newborns and TcB screening practices for each nursery were also collected. Multivariate regression analysis was used to identify characteristics independently associated with the TcB--TSB difference. RESULTS Data on 8319 TcB measurements were collected at 27 nursery sites; 925 TSB levels were matched to a TcB value. The mean TcB--TSB difference was 0.84 ± 1.78 mg/dL, and the correlation between paired measurements was 0.78. In the multivariate analysis, TcB--TSB differences were 0.67 mg/dL higher in African-American newborns than in neonates of other races (P < .001). The TcB--TSB difference also varied significantly based on brand of TcB meter used and hour of age of the infant. For 2.2% of paired measurements, the TcB measurement underestimated the TSB level by ≥ 3 mg/dL. CONCLUSIONS During routine clinical care, TcB measurement provided a reasonable estimate of TSB levels in healthy newborns. Discrepancies between TcB and TSB levels were increased in African-American newborns and varied based on brand of meter used.