The value of screening inpatients with creatine kinase testing.

with inhibitors such as a1-protease inhibitor and protein C (4, 11, 12 ). A changed glycation of the PSA forms occurs in the presence of prostate carcinoma and could be the reason for the change of the complex formation of PSA with various proteinase inhibitors (13 ). Thus, these minor PSA complexes produce such concentrations in PCa patients that the above mentioned gap appears. Other possible explanations for these discrepancies between BPH and PCa patients include the calibration of the assays, different recognition of multiple forms of f-PSA or t-PSA in the two groups of patients, and the lack of equimolarity of the tests. However, we believe these rather technical artifacts are ruled out as far as possible by the analytical data described above. To our knowledge of the literature, this phenomenon was not clearly pointed out until now (3–5, 14 ). One reason might be that, because of the analytical problems of overestimation mentioned above, the measurement of ACT-PSA concentrations could not be performed reliably in the past (6 ). When an improved assay for ACT-PSA was used, t-PSA values were frequently greater than the sum of f-PSA plus ACT-PSA, similar to our study (6 ). However, no additional conclusions were given by these authors. In conclusion, we believe that our results contradict the high expectations concerning the determination of ACTPSA or the ratio of ACT-PSA to t-PSA to improve the differentiation between PCa and BPH (15 ). The f-PSA/tPSA ratio, and not the ACT-PSA/t-PSA ratio, allowed the best discrimination between BPH and PCa patients. These data correspond to the findings described previously by Björk et al. (14 ). Other studies also showed that ACT-PSA concentration alone did not improve the specificity for PCa diagnostics over t-PSA (16 ). Therefore, a recently described PSA immunoassay that detects all complexed PSA forms, such as ACT-PSA, as well as the minor forms except PSA complexed to a2-macroglobulin may eliminate the problem of minor PSA forms as found in our study (17 ).