Dual monoclonal antibody immunoassay for free prostate-specific antigen

Abstract

Prostate‐specific antigen (PSA) is the most important tumor marker for early detection and monitoring of prostate cancer (PCa) patients. PSA is also elevated in many patients with benign prostatic hyperplasia (BPH). The study of the serum PSA forms, free PSA (f‐PSA) and PSA complexed with α1‐antichymotrypsin (PSA‐ACT), may improve the discrimination between PCa and BPH. An immunoassay specific for f‐PSA is reported with very low cross‐reactivity (0.7%) to PSA‐ACT. Serum specimens from BPH and PCa patients (determined by biopsy) with PSA levels from <1 to >100 ng/ml were tested. No f‐PSA was detected in serum specimens from normal females (N = 50). Low levels (0–0.3 ng/ml) were detected in specimens from healthy males (N = 60). In specimens from PCa and BPH patients, the f‐PSA to total PSA ratio (f/t) was found to range from 1% to higher than 60%. While maintaining an 80% sensitivity for cancer, the f/t ratio improved specificity to approximately 80%, as compared to 55% for total PSA alone. The receiver operating characteristics (ROC) curve analysis of the f/t ratio displayed a greater area under the plot (0.84) compared to total PSA alone (0.745). The results demonstrate that the f/t ratio significantly increases specificity for PCa detection compared to total PSA alone, showing the potential clinical value of the f‐PSA immunoassay. © 1996 Wiley‐Liss, Inc.

Using the free-to-total prostate-specific antigen ratio to detect prostate cancer in men with nonspecific elevations of prostate-specific antigen levels

“…91 Seventeen of the 21 studies presented data on investigator-selected cut points. [73][74][75][76][77][78][79][80][81]83,84,[86][87][88][89][90] Table 1 shows the number of studies meeting the methodologic criteria used to evaluate validity and generalizability. Thirteen studies used needle biopsy as the single reference standard, but none of them used long-term clinical follow-up to define true negative test results.…”

The value of γ‐seminoprotein in combination with prostate specific antigen in detecting prostate cancer

“…The improved diagnostic efficacy of the γ‐Sm/PSA ratio has been comprehensively demonstrated by an increased area under the ROC curve, where the entire spectrum of sensitivity and specificity pairs is graphed and compared with that of total PSA. A ROC curve analysis of the PSA F/T ratio has been report‐ ed to yield a greater area under the curve than total PSA alone, 19 although it has been suggested that free PSA values do not provide additional diagnostic benefit compared with total PSA in screening populations 20 . In the present study, the area under the ROC curve of PSA was 0.54 in this PSA range, sug‐ gesting that differentiation between BPH and prostate cancer using the PSA values is not significantly better than by chance (AUC = 0.5).…”

Prostate Specific Antigen

“…The amount of radioactivity bound to the bead is proportional to the amount of analyte present in the test sample, which is determined from a calibrated curve by using a linear or cubic spline equation to interpolate between calibrators. The current Tandem-R free PSA assay should not be confused with earlier research prototypes previously reported by Wang et al [19]. The research prototype was a sequential assay using streptavidin-coated microplates, biotinylated anti-free PSA (PSB999), and europium-labeled anti-PSA (PSM773).…”