Afshan Sumera , Sulaiman Ahmed , SM Adnan Ali , Rafiq Khanani
Objective: To evaluate efficiency of Naked Eye Single Tube Red cell Osmotic Fragility Test (NESTROFT) as a marker of clinical differentiation between β-thalassemia trait (BTT) & Iron deficiency anemia; to rule out potential bias of NESTROFT with regards to its sensitivity and specificity in cases with coincident iron deficiency anemia.
Materials & Methods: This was a case control study on 503 subjects, carried out at Dow Diagnostics Research & Reference Lab (DDRRL) during the period from December 2009 to August 2010. Subjects were categorized into three groups based on red cell indices, preformed on automated hematology analyser (cell tac alpha, Nihon Kohden, Japan). Group I, comprised of control subjects with normal red cell indices, Group II comprised of case subjects with microcytosis MCV < 80 fL, normal ferritin levels and HbA2 > 3.5% on Hb Electrophoresis and Group III included subjects with proven Iron Deficiency Anemia (IDA) i.e., low serum ferritin levels; hemogram & peripheral smears suggestive of iron deficiency anemia. NESTROFT was performed on all cases. Sensitivity, Specificity, Positive Predictive Value and Negative Predictive Value were calculated. Differential Diagnosis of IDA & BTT was justified by testing serum Ferritin and Hemoglobin Electrophoresis (showing increased HbA2 (≥3.5%) on cellulose acetate at an alkaline pH in cases with BTT). Data analysis was done on SPSS version 16.0.
Results: Out of total 503 study subjects, microcytosis was found in 253 subjects. Majority of our microcytosis cases were with IDA n=174/253 (69%), while BTT cases were n=73/253 (29%). Sensitivity of NESTROFT was observed 93%, Specificity was 88% with Positive Predictive Value of 74% & Negative Predictive Value of 97%. NESTRODT was concomitantly positive in 13% IDA cases while it remained negative in 88% of subjects with IDA. For differentiation between IDA and BTT, red cell indices (MCV, MCH & MCHC), RBC count, & RDW% demonstrated statistically significant differences (P < 0.05).
Conclusion: We conclude that NESTROFT is sensitive and specific marker in differentiating beta-thalassemia trait from iron deficiency anemia.
