The erythema index [EI = log (Sred) – log (Sgreen)], where S is the brightness of the palpebral conjunctiva in the relevant color channel) was found to be significantly associated with measured Hb (the r2 could be up to 0.397), based on which the sensitivity and specificity for anemia (Hb <11.0 g/dL) were 57.0 and 83.0% (20). This evidence concerns the gene GSTM1 and Erythema.