The clinical value of the Enzymun-Test for total and free PSA--a multicentre evaluation

This study examined the clinical relevance of the determination of free PSA (f-PSA) in addition to total PSA (t-PSA) in 6 study groups.

Both total PSA- and free PSA-values of sera samples obtained pretherapeutically from 455 patients with carcinoma (PCA) and 680 patients with benign hyperplasia of the prostate (BPH) were analyzed by means of Enzymun-Test PSA and Enzymun-Test Free PSA (Boehringer Mannheim GmbH, Germany).

At 95% specificity (true negative test results), a cutoff value of 13.6 [micrograms/L] was obtained for total PSA (34 patients with BPH [5%] were above this value). For this cutoff value we calculated a sensitivity (true positive test results) of 44%. Using the same criteria for the ratio Q = f-PSA:t-PSA a cutoff of 0.13 was found again at a specificity of 95%. In a second step only patients with total PSA values below the cutoff level of 13.6 [micrograms/L]) were considered. Out of these patients 26 of 646 with BPH and 108 of 257 with PCA were below the above mentioned ratio (Q = 0.13). Considering both steps (total PSA and Q) 306 patients with PCA were detected correctly and 60 patients with BPH would have been biopsied unnecessarily.

High total PSA levels are a very good indicator for the presence of prostate cancer. There is still concern to improve the differentiation of the diagnosis between BPH and PCA, when an intermediate or low value (< or = 95% specificity) is observed. The determination of the ratio is only useful in this range. It is more powerful at discriminating between PCA and BPH than t-PSA alone and may contribute to a reduction in unnecessary invasive techniques.