ERYTHROPOIETIN DEFICIENCY AND RELATIVE RESISTANCE CAUSE ANEMIA IN POSTRENAL TRANSPLANT RECIPIENTS WITH NORMAL RENAL-FUNCTION

Background. Following successful renal transplantation, blood erythrop oietin (Epo) levels peak in two phases during the first 2-3 months, an d blood haemoglobin/haematocrit (Hb/Hct) levels are restored to normal in a period of 2-6 months. However, some transplant recipients contin ue to remain anaemic in spite of normal graft function and in the abse nce of recognizable causes. The role of endogenous Epo production in t he causation of anaemia in such patients is poorly understood and has been investigated in this study. Methods. Twenty-three post-renal tran splant recipients with stable normal renal function were studied. Elev en of these patients had normal Hb/Hct levels (group 1) and served as control for the rest 12 patients with anaemia (group 2). Patients incl uded in group 2 had no readily recognizable cause for their anaemia. O ther laboratory and clinical findings were similar in both groups. Pat ients with erythrocytosis were excluded. Serum Epo levels were measure d in all patients. Five patients in group 2 were treated with recombin ant human erythropoietin (rHuEpo) and their erythropoietic response wa s assessed. rHuEpo was discontinued when the target Hb/Hct levels (low est normal range) were achieved and the patients were followed up for a further period of 9-12 months. Results. Five patients in group 1 had normal expected serum Epo levels whereas the other six patients had i nappropriately high serum Epo levels with respect to their Hb/Hct stat us suggestive of relative 'Epo resistance'. Serum Epo levels in all pa tients except two in group 2 were low indicative of 'Epo deficiency'. The two exceptional patients in group 2 had higher serum Epo levels in the presence of anaemia suggestive of relative 'Epo resistance'. All five patients treated with rHuEpo responded adequately by achieving no rmal Hb/Hct levels. Three of them were originally 'Epo deficient' and they reached target Hb/Hct levels in a mean period of 4 weeks, requiri ng a mean cumulative rHuEpo dose of 428.3 units/kg. The other two pati ents with higher initial serum Epo levels, and considered to be 'Epo r esistant', required an average of 11 weeks of treatment and a mean cum ulative rHuEpo dose of 1582.5 units/kg, indicating an increased Epo de mand. On cessation of therapy the Hb/Hct levels fell in all five patie nts to pretreatment values in 6 months. Conclusions. There are importa nt variations in the endogenous Epo production in renal transplant pat ients with normal renal function, the cause of which is not clear. Epo deficiency and relative Epo resistance play a causative role for anae mia in some post-renal transplant recipients with stable normal renal function. They respond adequately to rHuEpo administration.