Empty iron stores in children and young adults--the diagnostic accuracy of MCV, MCH, and MCHC.

INTRODUCTION

Erythrocyte mean cell volume (MCV) is used clinically to classify anemia, and normal values may be used to exclude iron deficiency. We have studied the diagnostic accuracy of MCV and the related measures mean cell hemoglobin (MCH) and mean cell hemoglobin concentration (MCHC) in diagnosing empty iron stores in children and young adults.

METHODS

Diagnostic accuracy of MCV, MCH, and MCHC was studied by ROC curve analysis in 6443 ambulant patients aged 0.5-25 years, of which 476 were anemic. In all patients, blood hemoglobin, MCV, MCH, and serum ferritin were measured in specimens sampled at the same time. MCHC was calculated as MCH divided by MCV. The gold standard of empty iron stores was s-ferritin <10, 15, or 20 μg/L. The cutoff limit of MCV giving 90% sensitivity in diagnosing serum ferritin <15 μg/L was constructed using quantile regression.

RESULTS

Generally, MCH was slightly more accurate than MCV and MCHC. In the whole study population, the area under the ROC curve was 0.68-0.93 for MCV, 0.73-0.96 for MCH, and 0.68-0.87 for MCHC; and 0.70-0.86, 0.71-0.89, and 0.68-0.88, respectively, in the anemic subpopulation. At the cutoff limits of MCV giving a sensitivity of 90% at all ages in anemic patients, the specificity was about 50%.

CONCLUSION

Mean cell hemoglobin, MCH, and MCHC are only moderately accurate in diagnosing empty iron stores in children and young adults, and normal values of these tests do not exclude empty iron stores in anemic patients.