(362) Identifying Hemolytic Disease of the Fetus and Newborn (HDFN) in a Large Integrated Healthcare System

HDFN is a blood disorder caused by maternal-fetal red cell antigen incompatibility. This study aims to identify HDFN cases using electronic health records (EHR) of pregnant patients.

Study Design:

A retrospective cohort study was performed among pregnant patients receiving obstetrical care at Kaiser Permanente Southern California (01/01/2008–06/30/2022). Using structured (e.g., diagnostic/procedural codes and laboratory results) and unstructured (clinical notes analyzed via Natural Language Processing) data abstracted from EHRs, we extracted HDFN-specific “indicators” (including antibody test, antibody titer, HDFN diagnosis, blood transfusion/intravenous immunoglobulin treatment [IVIG], and jaundice/phototherapy) to identify potential HDFN patients. Chart reviews and adjudication by a clinical investigator were performed on select combinations of indicators for case ascertainment. HDFN due to ABO isoimmunization was excluded. The HDFN frequency and proportion of each combination were calculated.

Results:

Among 572,328 pregnancies, indicators for maternal positive antibody test (2.72%), maternal abnormal titer (0.08%), maternal/infant HDFN diagnosis (0.45%), maternal/infant transfusion/IVIG treatment (0.64%), and infant jaundice/phototherapy (35.40%) were extracted. Pregnancies with 8 different indicator combinations (out of 24 total combinations) plus 91 pregnancies from other combinations were chart reviewed. 105 (30.97%) HDFN pregnancies were confirmed (Table). A majority of HDFN pregnancies (n=87) had at least the following indicators: maternal positive antibody test, maternal abnormal titer, and maternal/infant HDFN diagnosis. Those with all 5 indicators had a confirmed HDFN rate of 89%.

Conclusion:

We successfully identified HDFN patients using a combination of medical indicators extracted from structured and unstructured data that may be used in future pharmacoepidemiologic studies. Traditional indicators (positive antibody test results, high titers, and clinical codes) alone did not identify HDFN pregnancies, highlighting an unmet need for improved practices in HDFN coding.