THE RATIO OF FREE TO TOTAL PROSTATE-SPECIFIC ANTIGEN - AN ADVANTAGEOUS ADDITION 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 (t-PSA). Patients and Methods: Both total PSA-and free PSA-values of frozen sera obtained pretherapeu tically from 80 patients with carcinoma (PC) and 171 patients with ben ign hyperplasia of the prostate (BPH) were analysed by means of PSA IR MA and FREE PSA IRMA (IMMUNOCORP/IBL). Results: At 95% specificity (tr ue negative test results), a cut-off value of 16.8 [mu g/L] was obtain ed for total PSA (9 patients with BPH [5%] were above this value). For this cut-off value we calculated a sensitivity (true positive test re sults) of 41%. Using the same criteria for the ratio Q= f-PSA : t-PSA a cut-off of 0.083 was found again at a specificity of 95%. In a secon d step only patients with total PSA values below the cut-off level of 16.8 [mu g/L]) were considered. Of these patients 11 of 160 with BPH ( missing values=1) and 13 of 33 with PC (missing values=2) were below t he above mentioned ratio (Q=0.083). Considering both steps (total PSA and Q) 46 patients with PC were detected correctly and 20 patients wit h BPH would have been biopsied unnecessarily (positive biopsy rate: 70 %). Conclusion. High total PSA levels are a very good indicator for th e presence of prostate cancer. There is still concern to improve the d ifferentiation between the diagnosis between BPH and PC, when an inter mediate or low value (less than or equal to 95% specificity) is observ ed. The determination of Q is only useful in this range and might be h elpful for the clinician's decision to apply or avoid biopsy.