Retrospective analysis of direct antiglobulin test positivity at tertiary academic hospital over 10 years.

Background: Hemolytic disease of the fetus and newborn (HDFN) is a clinically significant problem that may potentially affect any pregnancy. Direct antiglobulin test (DAT) is considered to be an important test in identifying newborns who are suspected to have HDN. This study aims in reviewing data regarding a positive DAT result concerning etiology and the development of HDN over a period of 10 years.

Study Design And Methods: A retrospective study of all neonates with a positive DAT result between January 2011 and December 2020 was performed. Data were obtained from patients' electronic hospital files, transfusion medicine databases, and medical birth records. Laboratory parameters along with clinical interventions in neonates with a DAT-positive result and a comparison group of DAT-negative neonates were performed.

Results: 36,000 deliveries were registered in this period. 176 (2.65 %) neonates had a positive DAT result. ABO-incompatibility was the most common cause with 59.1 %; Rh incompatibility 13.8 %, minor blood group incompatibility, and other RBC-related antibodies 10.1 %, and unspecified etiology in 17 % of cases. Among DAT-positive cases, 32.7 % of neonates were diagnosed with HDN. ABO-incompatibility was the major reason as well. Initial mean total bilirubin levels were higher in the DAT-positive group than the control group (p < 0.001), and these neonates also had a lower initial hemoglobin level (p < 0.001). The need for therapeutic interventions was significantly higher in DAT-positive neonates (p < 0.001) as 86.8 % underwent phototherapy, with 32.7 %, and 17.6 % receiving exchange transfusion (ET) and intravenous immunoglobulin (IVIG), respectively.

Conclusion: In conclusion, ABO incompatibility was the most common cause for neonatal DAT positivity. Besides the common causes of DAT positivity, there would be rare but important conditions that may lead to a positive result, such as antibodies passively acquired from mothers in the context of alloimmunizations or using drugs. In addition, as a high rate of therapeutic intervention was identified among neonates with a DAT-positive result, there is a crucial need for increasing awareness regarding early diagnosis of the condition, careful monitoring, and the employment of prenatal alloimmunization screening tests.