A multicenter clinical trial on the use of complexed prostate specific antigen in low prostate specific antigen concentrations

Purpose: The determination of complexed prostate specific antigen (cPSA) has been suggested to be promising for prostate cancer (PCa) diagnosis. In a multicenter trial we evaluate the diagnostic use of PSA forms in the low total PSA (tPSA) range. Materials and Methods: A total of 283 white men with and 417 without PCa and tPSA concentrations between 0 and 6 ng/ml were retrospectively analyzed. All 700 untreated subjects underwent a multisector needle biopsy of the prostate. The Elecsys analyser 1010 (Roche Diagnostics, Mannheim, Germany) was used for determination of tPSA and free PSA. Determination of cPSA and tPSA was performed using immunoassays of the Bayer Immuno 1 system (Bayer Diagnostics, Tarrytown, New York). Results: Receiver operating characteristics analyses for discrimination between cases with and without PCa were performed. The areas under the curves (AUC) for cPSA, tPSA and free-to-total PSA (f/tPSA) showed no significant differences in the tPSA ranges of 0 to 6 (700 cases), 0 to 4 (510) and 0.5 to 2.5 ng/ml (253). Within the tPSA range of 2.5 to 4 ng/ml (230 cases) the AUC for cPSA (0.61) was significantly larger than that for tPSA (Roche 0.51, Bayer 0.54) but did not differ from the AUC of f/tPSA (Roche). On the basis of the cutoffs for 95% specificity or sensitivity, no significant increase in corresponding sensitivity or specificity was found between tPSA with cPSA. Conclusions: In the tPSA range of less than 4 ng/ml no improvement in diagnostic accuracy was shown between cPSA with tPSA or the ratio of f/tPSA. The search for a useful marker in the low PSA range must continue.