Clinical Usefulness of Flow Cytometry in Detection and Quantification of Fetomaternal Hemorrhage

> Objective: To compare the technique of immunofluorescence flow cytometry against traditional Kleihauer testing with respect to the sensitivity and specificity of clinical detection of fetomaternal hemorrhage. Methods: Blood samples from D-negative unsensitized postpartum women were analyzed by flow cytometry (customized, directly conjugated monoclonal anti-D) and Kleihauer testing using commercial kits as well as a manual technique. Results: Both flow cytometry and manual Kleihauer tests performed well in vitro against known standards, giving similar results with detectable fetal cells in the range of 2-10%. Correlation of in vivo results obtained by flow cytometry and either Kleihauer method was poor. The percentage of fetal red cells detected by flow cytometry was approximately twice that of the manual Kleihauer. Commercial Kleihauer testing proved unreliable in the in vivo setting. Conclusions: Flow cytometry offers a reliable alternative to traditional Kleihauer testing for detecting fetomaternal hemorrhage and may, with standardized methodology, help optimize immunoprophylaxis against erythroblastosis fetalis.