Effect of daily subcutaneous administration of recombinant erythropoietin on chronic anemia in rheumatoid arthritis.

Mean (+/- SD) serum erythropoietin (EPO) levels were 18.6 +/- 5.6 mU/ml in 180 normal Japanese subjects. Serum EPO levels were elevated with a negative correlation on a log scale (r = -0.864, P < 0.005) to hematocrit (Ht) values in anemic patients not associated with rheumatoid arthritis (RA) or chronic renal failure (CRF). Serum EPO levels in patients with RA (31.6 +/- 16.4 mU/ml) were relatively lower than those in normal subjects and anemic patients without RA or CRF when matched for comparative Ht values. Seven anemic patients with RA were treated by daily subcutaneous (sc) injection of recombinant EPO (rEPO, 500-1,000 U/day) for 4 weeks. The patients had initial Ht values of 25.1% or less and maintained stable clinical status. The treatment with rEPO raised serum EPO levels (53.8 +/- 15.2 mU/ml, P < 0.05), which resulted in an increase in Ht values (more than 3%) in 6 out of 7 patients with RA. The mean (+/- SD) Ht values at the end of the treatment with rEPO (500-1,000 U/day) were greater than those before the treatment in the 7 patients with RA (28.5 +/- 4.6 vs. 22.7 +/- 2.5%, P < 0.05). These findings suggest that chronic anemia associated with RA may be corrected by daily sc injection of a small dose of rEPO.