If the reticulocyte count corrected for anaemia (i. e., the reticulocyte “ index”) is low (< 20,000/ mm3 or < 20,000/ microlitre or < 0.5%), platelet and white blood cell counts are normal, and if no other cause of loss of effect has been found, anti-erythropoietin antibodies should be determined and bone marrow examination should be considered for diagnosis of PRCA.