131 Direct Antiglobulin Titer (DAT) Strength and Hyperbilirubinemia in Canadian Infants

Abstract

ABO incompatibility is a major risk factor for severe jaundice. Previous small studies have suggested that increasing DAT strength is associated with higher levels of bilirubin and greater need for phototherapy. There is no Canadian published data on DAT strength and hyperbilirubinemia. DAT strength is analyzed on all positive newborn DAT tests in our center and could therefore be evaluated with respect to these high-risk infants. To evaluate a large cohort of DAT-positive ABO incompatible Canadian newborns focusing on DAT strength, bilirubin levels and the need for phototherapy. A retrospective chart review of 1,437 DAT-positive newborns over a three-year period (total births of 23,628). Infants with risk factors in addition to being DAT positive were excluded. 841 eligible infants were included. DAT strength was categorized as W, 1+, 2+, 3+ and 4+. All bilirubin test results performed from birth until 200 hours of age were analyzed. Bilirubin levels at 12 and 24 hours of age as well as the need for phototherapy was evaluated Of the 841 eligible infants, 594 DAT tests were weak positive, 225 were 1+, 21 were 2+, and 1 was 3+. Newborns with higher DAT strengths were more likely to need phototherapy than newborns with lower DAT strengths. Mean plasma bilirubin levels were higher at 12 and 24 hours in newborns with higher DAT strengths with the difference between 2+ and Weak being significant (P = 0.0087). Newborns with higher DAT strengths were more likely to be at or above the threshold for phototherapy initiation at 12 hours of age. Relative risk: 2+ versus weak 6.18; 2+ versus 1 + 3.34 and 1+ versus weak 1.85. Newborns with higher DAT strengths were also more likely to be in the high-risk zone on the Bhutani nomogram at 12 hours of age. Relative risk: 2+ versus weak 3.37, 2+ versus 1 + 1.96 and 1+ versus weak 1.72. ABO incompatible newborns do not exhibit the most severe form of hemolytic jaundice. Higher DAT strength newborns were more likely to require phototherapy. Higher DAT strength newborns were more likely to have bilirubin levels in the high-risk zone and be at or above the threshold for phototherapy at 12 hours of age. The majority of DAT-positive ABO-incompatible newborns with no other risk factors did not require phototherapy and many remained in the low or low intermediate risk zones