Ratio of gamma-seminoprotein to prostate-specific antigen for the detection of prostate cancer: its discrimination power could be influenced by the assay methods of PSA and/or gamma-seminoprotein.
BACKGROUND
The ratio of gamma-seminoprotein (gamma-Sm) and prostate-specific antigen (PSA) has been regarded as being superior over PSA alone as a discriminator between prostate cancer and benign prostatic diseases. In previous studies, PSA and gamma-Sm were measured by the Eiken kit and the old-version or revised Chugai kit, respectively. We compared the power of gamma-Sm ratio with that of PSA alone when using Markit-M PSA assay and the revised Chugai gamma-Sm assay.


METHODS
Fifty-three patients with prostate cancer having no metastasis and 116 with benign prostatic diseases were enrolled in this study. Prostate-specific antigen was measured by Markit-M kit and gamma-Sm was measured by the revised Chugai kit. The discrimination power of gamma-Sm ratio and PSA alone was evaluated with receiver operating characteristic (ROC) curves. Comparisons between prostate cancer and benign diseases were performed with Mann Whitney U-test and Fisher's exact test.


RESULTS
The optimal cut-off value was set at 3.1 ng/mL for PSA and 0.935 for gamma-Sm ratio. Sensitivity, specificity and positive predictive value of PSA alone were 81.1, 81.0 and 66.2%, respectively, while those of gamma-Sm ratio were 73.6, 90.5 and 78.0%, respectively. There was no statistical significance in each value between PSA and gamma-Sm ratio. Areas under the ROC curves of PSA and gamma-Sm ratio were 0.881 and 0.866, respectively (P>0.05).


CONCLUSIONS
Contrary to the previous reports, gamma-Sm ratio and PSA were not different in the discrimination between prostate cancer and benign prostatic diseases, which suggested that the discrimination power of gamma-Sm ratio, and presumably that of the free PSA to total PSA ratio as well, could be considerably influenced by the assay kits for serum PSA and/or gamma-Sm (free PSA) used. Therefore, the clinical significance of gamma-Sm ratio should be evaluated for each PSA assay kit.
Akino
H
H
Department of Urology, Faculty of Medicine, Fukui Medical University, Japan.
Suzuki
Y
Y
Oyama
N
N
Kanamaru
H
H
Okada
K
K
D014408:Biomarkers, Tumor / Q000097:blood; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D008297:Male; D009367:Neoplasm Staging; D011237:Predictive Value of Tests; D017430:Prostate-Specific Antigen / Q000097:blood*; D011470:Prostatic Hyperplasia / Q000097:blood; D011471:Prostatic Neoplasms / Q000097:blood / Q000175:diagnosis*; D011933:Reagent Kits, Diagnostic; D012016:Reference Values; D012680:Sensitivity and Specificity
D014408:Biomarkers, Tumor; D011933:Reagent Kits, Diagnostic; D017430:Prostate-Specific Antigen