Prostate-specific antigen and its complexes with alpha 1-antichymotrypsin in the plasma of patients with prostatic disease.

OBJECTIVE

To improve the specificity and sensitivity of the prostate-specific-antigen (PSA) assay for the distinction between prostate cancer and benign prostate hyperplasia (BPH).

METHODS

Two sensitive immunoassays, one that measures free PSA and PSA complexed to alpha 1-antichymotrypsin (alpha 1-ACT) with the same efficiency (PSAag assay) and another that specifically measures the complex between PSA and alpha 1-ACT, have been designed to measure the PSA forms in the plasma of 84 patients with prostate disease and in the seminal plasma from 60 healthy individuals.

RESULTS

The proportion of plasma PSA in complex with alpha 1-ACT was significantly higher in the 34 patients with prostate cancer (89 +/- 12%, mean +/- SD; median, 91%) than in the 50 patients with BPH (71 +/- 12%; 73%) and did not correlate with the total amount of PSA. Normal seminal plasma (n = 60) had 2.1 +/- 0.6 mg/ml PSA, 175 +/- 62 microns/ml alpha 1-ACT and 9.6 +/- 3.4 micrograms/ml PSA: alpha 1-ACT complex.

CONCLUSION

These results confirm that PSA: alpha 1-ACT may be a good marker for a differential diagnosis of carcinoma of the prostate and BPH.