Age related changes of free and total prostate specific antigen in serum

PSA in serum exists in several molecular forms. The amount of free and tota l PSA and ratio are discussed to be useful to increase the ability of PSA t o distinguish prostate cancer from benign prostatic hyperplasia. Therefore, we tried to characterize the age related changes of free and total PSA in a German rural population. Methods: Serum samples were obtained from 697 me n. All study participants were between 20 and 79 years old and had no clini cal evidence of prostate cancer by serum PSA, digital rectal examination an d transrectal ultrasonography. The sera were kept frozen at -20 degrees C u ntil analysis and were assayed within 3 months after sampling. Free and tot al PSA values were determined employing a chemiluminescent enzyme immunoass ay (Immulite PSA and Freies PSA, DPC Biermann). Results: Free PSA, total PS A and the free-to-total PSA ratio (f-/t-ratio) demonstrated a correlation w ith patient age (r = 0.855, p = 0.0141; r = 0.857, p = 0.0137; r = -0.788, p = 0.0352). Employing the median and the 95% percentile the age-specific r eference ranges for free and total PSA were calculated. For the f-/t-ratio the median and the interquartile range (i.e. 25th-75th percentile) were cal culated Conclusion: In confirmation of a recent report, we found a direct c orrelation of free PSA, total PSA and the f-/t-ratio with age, whereas free and total PSA increases, the f-/t-ratio decreased with advancing age.