This study examined the clinical relevance of the determination of alpha 
1-antichymotrypsin complexed PSA (ACT-PSA) in addition to total PSA antigen 
(t-PSA).
PATIENTS AND METHODS: Both total PSA- and ACT-PSA-values of frozen sera obtained 
pretherapeutically from 93 patients with carcinoma (PC) and 132 patients with 
benign hyperplasia of the prostate (BPH) were analyzed by means of PSA 
sandwich-ELISA (Dianova GmbH) and ACT-PSA sandwich-ELISA (Dianova GmbH).
RESULTS: At 95% specificity (true negative test results), a cutoff value of 18.9 
[micrograms/L] was obtained for total PSA (7 patients with BPH [5%] were above 
this value). For this cutoff value we calculated a sensitivity (true positive 
test results) of 41%. Using the same criteria for the ratio Q = ACT-PSA: t-PSA 
(percentage of ACT-PSA) a cutoff of 6.0 was found again at a specificity of 95%. 
In a second step only patients with total PSA values below the cutoff level of 
18.9 [micrograms/L]) were considered. Out of these patients 119 of 125 with BPH 
and 3 of 54 with PC were below the above mentioned ratio (Q = 6.0). Considering 
both steps (total PSA and Q) 42 patients with PC were detected correctly and 15 
patients with BPH would have been biopsied unnecessarily.
CONCLUSION: 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 PC, when an intermediate or low value (< or = 95% 
specificity) is observed. The determination of Q = ACT-PSA: t-PSA is not to be 
recommended because it might not be helpful for the clinicians decision to 
perform biopsy.