Reduced erythropoietin response to anaemia in elderly patients with normocytic anaemia.

We studied the effect of age on the relationship between haemoglobin and serum erythropoietin (EPO) levels in anaemic patients. 568 patients over 70 years of age were compared with 137 patients under 70 and a reference group of 144 patients of all ages with proven iron deficiency. EPO was measured using a radioimmunoassay. We found that elderly patients with a normocytic anaemia (N = 375) had a statistically lower EPO response than younger patients with normocytic anaemia (N = 61) (p < 0.05) or patients of all ages with iron-deficiency anaemia (p < 0.05). There was no difference between the sexes. Elderly patients with microcytic or macrocytic anaemia had a normal EPO response as compared to the "gold standard" of iron deficiency. These findings suggest that a proportion of elderly patients with normocytic anaemia has an impaired EPO response.