Diagnostic efficiency of biological markers in blood serum on prostate cancer: a comparison of four different markers and 12 different methods

Continuous monitoring of prostatic acid phosphatase using self-indicating substrates

BACKGROUND

The continuous measurement of acid phosphatase (EC 3.1.3.2) activity in serum represents an analytical task not yet sufficiently accomplished.

METHODS

Introducing two novel substrates-2-chloro-4-nitrophenyl phosphate (CNP-P), which was preferred, and 4-nitronaphthyl-1-phosphate (NN-P)-an alternative assay to measure enzymatic activity was developed and compared with a modification of Hillmann's method (azo coupling of released naphth-1-ol with a diazonium compound). Apart from different substrate concentrations of 2-chloro-4-nitrophenyl phosphate, 4 mmol/l, and naphthyl-1-phosphate (N-P), 8 mmol/l (with Fast Red TR, 5 mmol/l), respectively, following identical conditions were selected: Citrate, 50 mmol/l, pH 5.75; pentane-1,5-diol, 150 mmol/l; tartrate, 60 mmol/l; 37 degrees C.

RESULTS

Whereas intensity and stability of the azo dye unpredictably depend on the albumin concentration of the sample, the direct test with 2-chloro-4-nitrophenyl phosphate resisted sample interferences, showed no intrinsic hydrolysis by albumin, relied on stable reagents and proved superior in sensitivity, precision and ease of handling. In measuring prostatic phosphatase, the proposed procedure closely correlated with Hillmann's method. The preliminary 0.95-reference intervals for adults were 1.2-3.9 kU/l and 5.8-14.8 U/l for total activity, respectively.

CONCLUSIONS

The direct assay of the enzyme is suited as an economic, rapid and robust method for mechanized or manual use.

A comparative study on expression of prostatic inhibin peptide, prostate acid phosphatase and prostate specific antigen in androgen independent human and rat prostate carcinoma cell lines

Prostatic inhibin peptide (PIP), consisting of 94 amino-acid residues is synthesized and secreted by the prostate gland. Previous studies on immunohistochemical localization of PIP in primary prostatic tumor and their metastasis, have documented the value of this peptide as a tumor marker for diagnosis of prostate cancer (PCa). The present study was undertaken to compare the expression of PIP with that of prostate specific antigen (PSA) and prostatic acid phosphatase (PAP) in androgen independent human PCa cell lines (PC-3, DU-145 and TSU-Prl) by immunoperoxidase technique. The results of the study indicated that the staining for PIP was more intense than that of PSA and PAP. The PSA staining was either weakly positive (PC-3) or totally absent (TSU-Prl and DU-145) while PAP staining was intense in PC-3 and moderate in the other two human cell lines. The intense staining observed for PIP in all of the androgen independent cell lines suggests that the synthesis and secretion of PIP is not primarily dependent on androgens. Furthermore, expression of these markers in Dunning rat cultured adenocarcinoma cell lines and tumors were studied. Positive staining for all three human tumor associated antigens (PIP, PSA and PAP) cross-reacting with the Dunning rat PCa cell lines and the tumors, suggest the suitability of this model for preclinical screening of various therapeutic agents.

CA-50 serum level in patients with prostate cancer

CA-50 antigen is considered to be a generalized carcinoma-associated antigen. CA-50 serum levels were measured by solid phase radioimmunoassay using a specific monoclonal antibody. Sera of 49 patients with prostatic cancer of different clinical stages, 43 patients suffering from BPH, and 28 healthy males were tested. Positive test results were observed in 57.1% of patients with prostate cancer values ranging from 42.9% in stage A to 66.7% in stage D. Increased CA-50 levels were found in 11.6% of patients with BPH.

Comparative study of the clinical usefulness of prostate specific antigen and prostatic acid phosphatase in prostatic disease

The clinical usefulness of prostate specific antigen (PSA) and prostatic acid phosphatase (PAP) activity measurements has been compared in 45 patients with benign prostatic hyperplasia (BPH) and 132 patients with prostatic carcinoma (PC), 21 of whom had metastatic disease (MPC) and 111 of whom had intracapsular cancer. No BPH patient had increased PAP but 47% had increased PSA. Of the PC patients only 27% had increased PAP and 70% increased PSA. All of the MPC patients had increased PSA but only 62% had increased PAP. Increased PAP was found only in MPC but increased PSA was also found in BPH. In identifying PC, the predictive value of an increased PSA concentration is 83% and an increased PAP activity is 100%. On the other hand, the predictive value of a normal PSA concentration is 51% and of a normal PAP activity only 34%. As the PAP test is much less efficient than the PSA test, it should be discontinued.

A comparative study on the diagnostic value of prostatic acid phosphatase (PAP) and prostatic specific antigen (PSA) in patients with carcinoma of the prostate gland

Serum prostatic-specific antigen (PSA) and prostatic acid phosphatase (PAP) were determined simultaneously in 241 patients presented to the Urology Department. The patients consisted of 140 prostatic carcinoma patients (34 newly diagnosed and 106 previously treated) and 101 patients with benign prostatic hypertrophy (BPH). Prostatic acid phosphatase was measured by two different methods, an enzymatic method (PAP-EA, Boehringer) with tartrate inhibition and an immunoenzymetric assay (PAP-IEMA, Hybritech). The concentration of prostatic specific antigen in serum was measured using a recently introduced immunoradiometric assay (PSA-IRMA, Hybritech). Receiver operating characteristic curves were constructed to compare the diagnostic value of the different tests at different cutoff values. The diagnostic efficiencies of the PAP-EA and the PAP-IEMA appeared to be similar. A better diagnostic efficiency for PSA compared to PAP was found independent of the cutoff value. The upper-normal limit of 2.7 micrograms/l for PSA, as suggested by the manufacturer and mentioned in the literature introduces too many false-positive results. We therefore selected 10 micrograms/l as the upper-normal limit for PSA (sensitivity 57%, specificity 88%). Combined sensitivity found for PAP + PSA was 37% with a specificity of 97%. A literature survey is included to allow better comparison with data published elsewhere.