In consideration of the highly close correlation of Rsf with MCV, MCH, and MCV in anemic patients, and the MCV, MCH, and MCV are the more sensitive and frequently-used indices of overt anemia than Hb concentrations in clinical practice, we used them to classify anemia also according to the single or simultaneous decrease in MCH, MCHC, and MCV levels compared with the optimal cutoff values calculated by the ROC curves. This evidence concerns the gene GSTM1 and anemia.