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Serum free prostate‐specific antigen in the diagnosis of prostate cancer

1997; Wiley; Volume: 80; Issue: 2 Linguagem: Inglês

10.1046/j.1464-410x.1997.00230.x

1365-2176

Hing Y. Leung, Leslie C. Lai, Jackie Day, Jennifer R. Thomson, David E. Neal, Freddie C. Hamdy,

Urologic and reproductive health conditions

Objective To determine the value of the ratio of free prostate‐specific antigen (fPSA) to total PSA (tPSA) in the diagnosis of benign prostatic hyperplasia (BPH) and prostate cancer in a cohort of patients undergoing prostatic transrectal ultrasonography (TRUS). Patients and methods The study comprised 153 patients (99 with BPH and 54 with prostate cancer) undergoing diagnostic TRUS of the prostate. Patients with a tPSA of >30 ng/mL were excluded from analysis. Free PSA was assayed using an immunoassay specific for unbound PSA (CanAg Diagnostics, Sweden). Total PSA was measured using the HybriTech Tandem‐R PSA immunoradiometric assay in routine clinical use and this estimate was validated using the CanAg tPSA assay. Results The measurements of tPSA from both assay systems correlated closely. The f/tPSA ratios in patients with prostate cancer were significantly lower than in those with BPH (median values 0.152 and 0.2, respectively, P <0.01). In patients with prostate cancer, the median f/t PSA levels apparently declined with increasing tPSA levels but in those with BPH, the levels of tPSA were not significantly associated with the f/tPSA ratio; the ratios did not vary significantly with age in either group. A f/tPSA ratio at a threshold of 0.16 had positive and negative predictive values of 44% and 74%, respectively; the corresponding values for a tPSA of >4 ng/mL were 30% and 52%. Conclusion The f/tPSA ratio differs significantly between patients with BPH and cancer but because there is a considerable overlap of f/tPSA ratios between the groups, f/tPSA values alone were not sufficiently specific to be used as a single diagnostic test.