Diagnostic Accuracy of an Erythrocyte Index-Based Protocol for Screening Beta Thalassemia Trait Among Antenatal Women in India.

INTRODUCTION: The prevalence of beta thalassemia trait (BTT) in India ranges from 1 to17%. Antenatal screening for BTT is the most acceptable screening strategy. Complete blood count (CBC) is a part of the routine antenatal checkup, and no extra resource would be required for BTT screening among antenatal women. METHODS: We conducted a retrospective analysis of the hematological laboratory reports of anemic antenatal women. Data were extracted from the laboratory reports of CBC and the HPLC (high-performance liquid chromatography) test. The diagnostic performance parameters that were assessed included accuracy, sensitivity, specificity, and predictive values (positive and negative) with 95% CI. We compared mean corpuscular volume (MCV), the mean corpuscular hemoglobin (MCH) level, and the Shine and Lal (SNL) index with HPLC (gold standard) for detecting BTT. An exploratory analysis was performed to derive the best combination of tests for screening BTT. RESULTS: Five hundred antenatal women participated in the study, of which 132 were positive for BTT by HPLC. Women with HbA2 value in the range of 3.5% to 9% were taken as positive for BTT. MCH was the most specific (89.9%), and the Shine and Lal index was the most sensitive test (90.9%) for detecting BTT. The MCH and the Shine and Lal index, when used in parallel, had the highest area under the curve for detecting BTT. CONCLUSION: The CBC-based indices are effective screening tools for BTT. Two tests, i.e., the MCH and the Shine and Lal index, when used in parallel, had high sensitivity for detecting BTT among antenatal women.