Diminished serum folic acid levels in renal transplant recipients.

Serum folic acid levels were determined by radioimmunoassay in 26 chronic hemodialysis patients, in 52 renal transplant recipients and in 20 healthy controls. In the dialyzed patients, the mean serum folic acid level was 3.37 +/- 1.25 ng/ml and was significantly lower than that of the controls (6.1 +/- 1.38 ng/ml, P less than 0.001). In renal transplant recipients the mean folic acid concentration was 4.09 +/- 1.58 ng/ml and was also significantly decreased (P less than 0.001). 15 (29 per cent) out of 52 renal transplant patients showed serum folic acid concentrations lower than 3.0 ng/ml. Diminished serum folic acid levels were found not only in patients shortly after surgery but also in cases with excellent graft function up to 6 years after transplantation. The highest serum folic acid level was observed in one transplant patient who had taken no azathioprine for 24 months. Macrocytosis was found in 52 per cent of our renal transplant patients. There was no significant difference between the serum folic acid levels of renal transplant recipients with (n = 27) and without (n = 25) macrocytosis; however, serum creatinine levels were significantly lower in cases revealing macrocytosis. Relative folic acid deficiency does not seem to be responsible for macrocytosis after renal transplantation. Macrocytosis was observed only in patients with good graft function treated with azathioprine. Serum vitamin B12 levels were within the normal range in both dialyzed and renal transplant patients.