Pre-analytical and biological variability of prostatic acid phosphatase and prostate-specific antigen in serum from patients with prostatic pathology.

We determined the pre-analytical and biological variation of prostatic acid phosphatase and prostate-specific antigen in the same patient samples. Prostatic acid phosphatase and prostate-specific antigen were both stable when stored for at least 3 weeks with acidification (acetate buffer) or without acidification, except for prostate-specific antigen in samples stored unacidified at 4 degrees C. A significant elevation of prostate-specific antigen was noted in four patients with benign prostatic hyperplasia between 1/2 and 6 hours after prostatic massage. No significant effect was shown of changes in the glomerular filtration rate on prostate-specific antigen concentration, in spite of its low molecular mass. The estimate of within-subject biological variation showed a coefficient of variation of 33.8% for prostatic acid phosphatase and 14% for prostate-specific antigen. Desirable analytical imprecisions based on these findings were about 17% for prostatic acid phosphatase and 7% for prostate-specific antigen, these goals being achieved in practice for marker values higher than or equal to the upper reference limit.