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.