Complexed PSA in routine diagnosis

Prostatic tumor tissue produces a more complex form of PSA (cPSA) than free PSA (fPSA). For the early detection of prostate cancer, cPSA is supposed to be more sensitive than the ratio of fPSA and tPSA. The aim of the study was to evaluate the diagnostic value of cPSA in the early detection of malignant prostatic tumor.

We evaluated the new cPSA test comparing it with the already routinely used fPSA and tPSA test. The study comprised a total of 100 patients with different urological symptoms attending the Division of Urology, University of Frankfurt, Germany. Biopsy and histological examination were performed in all cases. The histological report was compared with the laboratory results obtained by immunological and electrochemiluminescence methods.

Forty-one had a benign tumor of the prostatic gland and 59 had a malignant process diagnosed by histological examination. The cut-off level for cPSA was at 2.3 ng/ml. Within a range of 2.0-4.0 ng/ml tPSA and a cut-off of 2.3 ng/ml for cPSA we found a tumor sensitivity of the test in 92%, proved by the histological report. cPSA allows the detection of a malignant process at an earlier stage than tPSA and even within a "normal-range" of tPSA between 2.0-4.0 ng/ml. A concentration of tPSA between 4.1 and 10 ng/ml represents a grey zone. With measurement of cPSA we achieved, in 71% of our cases, a more specific result than in obtaining the PSA ratio. We did not observe any adverse result in the concentration of cPSA concerning manipulation of the prostatic gland as seen before in the measurement of fPSA. cPSA is much more stable regarding transportation and storage. There is no loss of concentration level observed up to -20 degrees C, whereas fPSA shows a loss of 10%.

We conclude that the new tumor marker cPSA is more specific in the concentration range of tPSA from 2.0-4.0 ng/ml, as well as in the grey zone between 4.0-10 ng/ml.