Evaluation of the direct antiglobulin (coombs’) test for identifying newborns at risk for hemolysis as determined by end-tidal carbon monoxide concentration (ETCOc); and comparison of the coombs’ test with ETCOc for detecting significant jaundice

Abstract

Objective: First, to determine the sensitivity, specificity, and positive predictive value (PPV) of the direct antiglobulin test (DAT) for significant hemolysis in the neonate, as referenced to end-tidal carbon monoxide, the criterion standard for estimating the rate of hemolysis; and second, to evaluate the predictive value of the two procedures for significant jaundice. Design: Consecutive term newborns admitted to the nursery of an inner-city university hospital over a 15-week period. DAT screening by the Blood Bank was performed on all. End-tidal carbon monoxide levels were obtained at 12 ± 6 and at 24 ± 6 hours of age. Infants of nonsmoking mothers whose 12-hour exhaled carbon monoxide level was ≥95th percentile were defined as having significant hemolysis. Results: n = 660; DAT was positive in 23 (3.5%). Using the 12-hour end-tidal carbon monoxide ≥3.2 μl/l (≥95th percentile) as reference (n = 499 nonsmokers), the sensitivity of the DAT was 38.5% (10 of 26) and specificity 98.5% (466 of 473) for the detection of significant hemolysis. The PPV of the DAT for significant hemolysis at 12 hours was 58.8% (10 of 17). For significant jaundice the PPV of end-tidal carbon monoxide was greater than that for DAT (65.4% vs 52.9%), although not statistically so (p = 0.25). The negative predictive values were similar. Conclusion: DAT fails to identify over half of the cases of significant hemolysis that are diagnosed by end-tidal carbon monoxide. A neonate with a positive DAT has about a 59% chance of having significant hemolysis. End-tidal carbon monoxide may also provide a more sensitive index for predicting significant jaundice.