Clinical value of human glandular kallikrein 2 and free and total prostate-specific antigen in serum from a population of men with prostate-specific antigen levels 3.0 ng/mL or greater
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OBJECTIVES: To investigate the clinical value of human glandular kallikrein 2 (hK2) compared with free (f) and total (t) prostate-specific antigen (PSA) in the early detection of prostate cancer (PCa). METHODS: In PCa screening conducted in 1995 to 1996 in Goteborg, Sweden, 5853 of 9811 randomly selected men (aged 50 to 66 years; median 61) accepted PSA testing; those with tPSA levels of 3. 0 ng/mL or greater were offered digital rectal examination, transrectal ultrasound, and sextant biopsies. Serum from 604 of 611 biopsied men (18% with positive digital rectal examinations, tPSA range 3.0 to 220 ng/mL, 144 men with PCa) was analyzed for hK2 (research assay) and tPSA and fPSA (Prostatus). Sera were stored at -20 degrees C for a maximum of 2 weeks for tPSA and fPSA and 3 years for hK2. RESULTS: hK2 levels and hK2 x tPSA/fPSA values were significantly elevated in men with PCa. Receiver operating characteristic data revealed that the area under the curve for hK2 x tPSA/fPSA was significantly greater than that for tPSA and greater, but not significantly greater, than that for percent fPSA. Also, the cancer-detecting sensitivity was significantly improved (P <0.05) using hK2 x tPSA/fPSA compared with tPSA and percent fPSA at specificity levels of 75% to 90%. At 75% specificity, a sensitivity of 74% was obtained compared with 64% or 54% using percent fPSA or tPSA; at 90% specificity, the corresponding sensitivity level was 55%, 41%, and 36%, respectively. CONCLUSIONS: Discrimination of men with and without PCa in a randomly selected population was improved by measuring hK2 in addition to tPSA and fPSA.