GSTM1 and anemia: The sub-group comprised 96,314 Danish patients, who had additional blood investigations from general practitioners within seven days of the included Hb sample. Proportions are presented with corresponding 95% confidence interval (CI). IDA - iron-deficiency anaemia. AOKC - anaemia by other known causes (deficiency of cobalamin, folate, etc.). ACD - anaemia of chronic disease.