The proportion of free to total prostate specific antigen: A method of detecting prostate carcinoma

✍ Scribed by Takayoshi Demura; Nobuo Shinohara; Motoyoshi Tanaka; Nobuyasu Enami; Hitoshi Chiba; Masaki Togashi; Nobuo Ohashi; Katsuya Nonomura; Tomohiko Koyanagi

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 630 KB
• Volume: 77
• Category: Article
• ISSN: 0008-543X
• DOI: 10.1002/(sici)1097-0142(19960315)77:6<1137::aid-cncr20>3.0.co;2-1

✦ Synopsis

BACKGROUND.

Prostate specific antigen (PSA) is the most useful marker for prostate carcinoma (Cap). However, the sensitivity and specificity for PSA are not sufficient for the diagnosis of organ-confined prostate carcinoma. Recent studies have revealed that anti-PSA antibody identifies both PSA complexed to alpha-l-antichymotrypsin and free PSA, whereas anti-gamma-seminoprotein antibody recognizes free PSA exclusively. To enhance the ability of PSA to detect CaP in patients with total PSA levels of 10 ng/mL or lower, we developed the ratio of gamma-serninoprotein and PSA (freeltotd PSA index). METHODS. We measured freeltotal PSA indices for 285 patients who had serum PSA levels of 10 ng/mL or lower and who were diagnosed pathologically.

RESULTS.

Of the 285 patients, 228 had no prostate carcinoma (NC) and 57 had Cap. The mean total PSA level for CaP (5.137 t 2.483 nglrnL; mean z standard deviation) was significantly greater ( P < 0.0001) than that for NC (3.251 ? 2.129).

The mean freeltotal PSA index for CaP (0.774 -e 0.468) was significantly lower (P < 0.0001) than that for NC (1.563 t 0.938). The sensitivity for the freeltotal PSA index was similar to that for total PSA (78.9% vs. 75.4%). However, the specificity, positive predictive value, and overall accuracy for the freeltotal PSA index (75.9%. 45%. and 76.5%, respectively) increased by 15-20% compared with those for total PSA (56.6%, 30.3%, and 60.4'36, respectively).

CONCLUSIONS.

The freeltotal PSA index improved the specificity of PSA without impairing the sensitivity in detecting CaP among patients with serum PSA levels of 10 ng/mL or lower. Cancer 19% 721137-43.0 1996American Cancer Sociefy.

KEYWORDS prostate carcinoma, prostate specific