FREE PSA - A USEFUL MARKER IN THE DIFFERENTIAL-DIAGNOSIS OF BENIGN HYPERPLASIA AND CANCER OF THE PROSTATE

This study examined the clinical relevance of the determination of fre e PSA (f-PSA) in addition to total PSA antigen (t-PSA). Patients and M ethods: Both total PSA- and free PSA-values of frozen sera obtained pr etherapeutically from 80 patients with carcinoma (PC) and 171 patients with benign hyperplasia of the prostate (BPH) were analyzed by means of PSA IR-MA and FREE IRMA (IMMUNO CORP/IBL). Results: At 95% specific ity (true negative test results), a cutoff value of 16.8 [mu g/L] was obtained for total PSA (9 patients with BPH [5%] were above this value ). For this cutoff value we calculated a sensitivity (true positive te st results) of 41%. Using the same criteria for the ratio Q = f-PSA:t- PSA a cutoff of 0.083 was found again at a specificity of 95%. In a se cond step only patients with total PSA values below the cutoff level o f 16.8 (mu g/L) were considered. Out of these patients 11 of 160 with BPH (missing values = 1) and 13 of 33 with PC (missing values = 2) wer e below the above mentioned ratio (Q = 0.083). Considering both steps (total PSA and Q) 46 patients with PC were detected correctly and 20 p atients with BPH would have been biopsied unnecessarily (positive biop sy rate: 70%). Conclusion: High total PSA levels are a very good indic ator for the presence of prostate cancer. There is still concern to im prove the differentiation of the diagnosis between BPH and PC, when an intermediate or low value (less than or equal to 95% specificity) is observed. The determination of Q is only useful in this range and migh t be helpful for the clinicians decision to apply or avoid biopsy.