Daily variability of serum prostate-specific antigen in men over 50 years of age.

In order to investigate the variability of serum prostate-specific antigen (PSA) levels a total of 44 men 50 years or older with normal digital rectal examination were enrolled. Blood samples were obtained three times within a day, and, immediately before and 72 hours after hospitalisation. Alterations in serum PSA value during the day and after hospitalisation, which might affect clinical decision, occurred in 15% of the cases with borderline PSA values. The results indicate that there may be significant changes in serum PSA levels within a day and after hospitalisation.