Serum concentration of prostate-specific antigen in relation to prostate volume in 50 healthy middle-aged men

Fifty men without symptoms of prostatic disease, aged 40 to 66 years, were studied with respect to serum concentration of prostate-specific antigen (PSA) and volume of the prostate gland. PSA was determined with two immunometric assays, one using a radioactive label, the other a nonisotopic label. Prostate volume was determined by transrectal ultrasound examination using two different modes of evaluation and assessed by rectal examination. The simpler "ellipsoid method" underestimated the volume by 20% compared to planimetry of several sections but they were well correlated to each other. It was found that prostate volume increased by 0.4 ml per year of age increase. There was a curvilinear relationship between serum PSA concentration and prostate volume determined by ultrasound; no statistically significant relationship was found between PSA concentration and prostate volume by rectal examination. The results indicate that the diagnostic value of serum PSA, for prostatic malignancy, will increase if values are related to prostate volume determined by ultrasound examination.