Time-resolved immunofluorometric assay of human prostate-specific antigen

Abstract

Assay of human serum prostate-specific antigen (PSA) is gaining importance in diagnosis and follow-up of prostatic cancer. In this time-resolved immunofluorometric assay of PSA, strip-wells were coated with a polyclonal antibody against PSA. To prepare the label, a monoclonal antibody displaying high affinity towards PSA was purified and derivatized with diethylenetriaminepentaacetic acid. With use of this derivative, seven to eight Eu atoms could be combined with one antibody molecule with no decrease in immunoreactivity. The minimum detectable concentration of PSA was 0.12 microgram/L. In 60 of 63 women studied, the PSA concentration in serum was less than 0.2 microgram/L. The increase in PSA in serum of asymptomatic men 51 years old or older, as compared with that for younger subjects, was possibly a result of "occult" prostatic hyperplasia. Most of the patients with prostatic hyperplasia or prostatic cancer had higher PSA concentrations than did subjects of ages less than 50 years or asymptomatic age-matched healthy subjects. Results compared favorably with those by an established technique relying on the use of radioactive label. Our method for measuring PSA in human serum is convenient, inexpensive, and well compatible with present clinical practice.