Impact of chronic dialysis on serum PSA, free PSA, and free/total PSA ratio: is prostate cancer detection compromised in patients receiving long-term dialysis?

Abstract

Objectives. The increased incidence of malignancy (ie, prostate cancer) in patients with end-stage renal failure is well known. However, little is known of the impact of hemodialysis and various membrane types on total and free prostate-specific antigen (PSA). We prospectively studied the impact of high- and low-flux dialysis membranes and kidney function on total PSA (tPSA), free PSA (fPSA), and free/total PSA ratio (f/t PSA). Methods. A total of 149 men were included. tPSA, fPSA, and f/t PSA were measured before and immediately after dialysis with high-flux (n = 101) and low-flux (n = 48) membranes in the serum and in the dialysis ultrafiltrate. A multivariate analysis of the impact of kidney function and age on the rate of change of all parameters was performed. Results. Overall, a significant decrease of fPSA (from 0.49 ± 0.3 to 0.35 ± 0.3 ng/mL, P <0.0001) and f/t PSA (from 45 ± 19% to 38 ± 13%, P <0.0001) and a nonsignificant decrease in serum tPSA were observed. However, fPSA (from 0.51 ± 0.5 to 0.27 ± 0.3 ng/mL, P <0.0001) and f/t PSA (from 47 ± 19% to 31 ± 18%, P < 0.0001) decreased significantly in high-flux membranes only. The ultrafiltrate contained 100% fPSA in high-flux membranes and no fPSA in low-flux membranes. Age, serum creatinine, blood urea nitrogen, and dialysis evaluation parameters (Kt/V) had no impact on correlation with changes in tPSA and fPSA. Conclusions. tPSA molecules do not pass high- and low-flux membranes; fPSA passes high-flux membranes only. The nonsignificant decrease of tPSA is due to adsorption to both dialysis membranes. Although tPSA can safely be used to screen patients on dialysis, independently from the dialysis procedure and membrane, fPSA and f/t PSA are only reliable with low-flux membranes. Finally, we can state that the fPSA is most probably cleared through the kidneys by glomerular filtration.