Diagnostic accuracy of mean corpuscular volume in detecting coexisting iron deficiency in patients of sickle cell disorders: A hospital-based study

Background:Co-existing iron deficiency in patients of sickle cell disease (SCD) and trait may worsen anemia, and adversely affect neuro-cognitive development and growth. Determining a cut-off below which Mean corpuscular Volume (MCV) can predict iron deficiency in SCD patients can preclude use of more expensive test serum ferritin.Aims:This study was conducted to determine the diagnostic accuracy of low MCV in detecting iron deficiency compared to serum ferritin levels in patients with SCD.Methods:60 consecutive patients with SS or AS pattern on hemoglobin electrophoresis were enrolled. The index test (MCV) and the reference standard test (serum ferritin) were performed in a blind and independent manner. The measures of diagnostic accuracy were calculated and the precision of the point estimates were expressed by 95% confidence intervals. As MCV is a continuous variable, we also used multi-level likelihood ratios to compute diagnostic accuracy of MCV at several cut-points.Results:The sensitivity of low MCV in detecting iron deficiency was 40.0% (95% CI-20.0-63.6), the specificity was 78.4% (95% CI-61.3-89.6) using serum ferritin as a reference standard. The sensitivity and specificity of predicting coexisting iron deficiency at this point was 60.9% (CI-38.6-80.3%) and 75.7% (CI-58.8-88.2%) respectively.Conclusions:The low sensitivity (40%) of microcytosis in detecting iron deficiency indicates that many cases will be missed if MCV alone is used to detect co-existing iron deficiency anemia in SCD patients. No single test is good enough to detect co-existing iron deficiency and a combination of tests might be useful.