The Reply

Abstract

The letter from Dr. Jolobe was read with interest. We do not doubt the cogent point that many of our subjects could have been identified by a low mean corpuscular hemoglobin (MCH). Further, both the mean corpuscular volume (MCV) and MCH will change with iron deficiency, with the red cells gradually becoming microcytic and hypochromic.1Auerbach M. Adamson J. How we diagnose and treat iron deficiency.Am J Hematol. 2015; 91: 31-38Crossref PubMed Scopus (154) Google Scholar However, in iron deficiency anemia the hemoglobin falls before the indices, and these are relatively late changes compared with changes in serum and storage iron. Subsequently, we did not use the red cell indices as an indicator of iron need or response and do not have the requested information available because it was not part of the study design. This decision is supported by a recent review of microcytic anemia in which the MCH was not mentioned.2Deloughery T. Microcytic anemia.N Engl J Med. 2007; 357: 93-94PubMed Google Scholar Nonetheless we have no doubt that Jolobe is correct and that many would have been captured by a low MCH. We did not require microcytosis or hypochromia as an entrance criterion, only oral iron intolerance, ineffectiveness, or contraindication and anemia as defined by a hemoglobin of <10.5 g/dL in the second trimester or <11.0 g/dL in the third, plus a serum ferritin of <20 ng/mL or a percent transferrin saturation of <16. Had we used the MCH we would have missed those with mild normochromic anemia and iron deficiency.3Auerbach M. James S. Nicoletti M. et al.Results of the first American prospective study of intravenous iron in oral iron intolerant iron deficient gravidas.Am J Med. 2017; 130: 1402-1407Abstract Full Text Full Text PDF PubMed Scopus (19) Google Scholar Another issue that may have been confounding had we elected to use indices as study criteria is the lack of specificity. In Jolobe's letter, it is prudently pointed out that only 82% of iron-deficient individuals are identified using the MCH. A similar percentage is identified by the MCV. The remaining 18% with normochromic iron deficiency would have remained unidentified. Further, the red cell indices may be low in thalassemia minor or inflammation and may be confusing. We believe the serum ferritin (if not elevated as an acute phase reactant) and percent transferrin saturation are the more reliable and accepted indicators of iron need and response to iron repletion, as clearly indicated by our data. The accuracy and subjection to artifact of the MCV and MCH vary by the analyzer used. With our Medonic M Series, the MCV and hemoglobin are measured and the MCH calculated. The same is true with the Coulter and Advia devices but not the Sysmex XN, which measures the MCH and hematocrit and calculates the MCV. Using the MCH in our practice may have been suboptimal. Nonetheless there are those who believe the measurement of MCH on the newer analyzers suffers from fewer artifacts and should be used more widely and believe that future studies should examine whether the MCH has similar or better value than the more widely used MCV for diagnosis of iron deficiency.4Schrier S. Causes of iron deficiency in adults.in: Tirnauer J. UpToDate. UpToDate, Walters-Kluver (Pub), Waltham, MA2017Google Scholar We hope we have adequately explained why we did not capture and therefore cannot supply the requested information; however we do not, for a moment, wish to minimize the potential interest it might have generated. Mean Cell Hemoglobin in Normocytic Iron Deficiency AnemiaThe American Journal of MedicineVol. 131Issue 4PreviewThe observation that normocytic anemia (characterized by mean cell volume averaging 81.23 fL) could coexist with unequivocal iron deficiency1 raises the possibility that some of those patients might have been characterized by low mean cell hemoglobin (MCH). This possibility arises because low MCH has been proposed as a screening test for iron deficiency anemia on the basis that, in that study, among 830 patients with MCH <28 pg, 679 (82%) had both low MCH and iron deficiency.2 Accordingly, it would be interesting to ascertain what proportion of the 60 patients in the recent study1 proved to have pretreatment MCH values amounting to <28 pg. Full-Text PDF