Laboratory Indices in Patients with Positive and Borderline Flow Cytometry Eosin-5-Maleimide-Screening Test Results for Hereditary Spherocytosis.

Objective: To evaluate laboratory indices in patients with hereditary spherocytosis, with positive and borderline flow cytometry eosin-5-melamide (EMA)-bound red blood cells screening test.

Study Design: We compared laboratory indices of 151 samples obtained from 139 different individual patients with negative, borderline, or positive EMA-test results. We also compared the clinical data of the patients in each EMA test results group.

Results: Borderline EMA-test results were obtained for 13 patients and were associated with more severe anemia, and lower reticulocyte count and reticulocyte production index compared with samples with positive EMA-test results. A receiving operator characteristic analysis identified mean corpuscular hemoglobin concentration of <32.5 g/dL as a cut-off, between positive/borderline and negative test results with 100% sensitivity. A higher prevalence of clinical markers typical of hereditary spherocytosis was found in patients with borderline or positive compared with negative EMA test samples.

Conclusions: Based on laboratory data, borderline EMA-test results may be an indication of a more severe form of hereditary spherocytosis. Using mean corpuscular hemoglobin concentration as a cut-off may help predict and reduce negative EMA tests without compromising sensitivity. This finding needs to be further validated in other flow cytometry laboratories with a large EMA test sample pool.