1994 Volume 85 Issue 10 Pages 1494-1501
The TOSOH II PA (AIA-PACK PA in the U. S. A.) monoclonal immunoenzyme assay was used and the clinical usefulness of prostate specific antigen (PSA) was evaluated in 39 men with prostatic cancer and 32 men with benign prostatic hyperplasia (BPH) confirmed pathologically. We evaluated the lower limit of detection in this assay by the mean PSA level plue 3 standard deviations in 5 separate experiments with a zero control sera as well as the mean PSA level minus 3 standard deviations in 5 separate experiments with serial dilutions of a known concentration of PSA. PSA concentrations of 0 to 0.25ng/ml could not be distinguished from the zero control. Therefore, we set the lower limit of detection for the assay as 0.25ng/ml. At our laboratory, the normal standard value was determined by the mean PSA level plus 3 standard deviations in 79 healthy men as 2.3ng/ml. Of patients that underwent radical cystoprostatectomy for bladder cancer, all had PSA levels less than 0.25ng/ml, while only 6% had PAP levels less than 0.11ng/ml, the lower limit of detection in the TOSOH II PAP assay. We compared TOSOH II PA with Markit PA, a commonly used assay in Japan. Although there was a close linear correlation (r=0.90) between the TOSOH II PA and Markit PA, the difference of slope in the linear regression lines was great, it was thought due to anti-PSA antibodies in each assay recognizing different epitopes of PSA in the blood. In all of 39 patients with prostatic cancer, serum PSA levels were more than 2.3ng/ml, the normal upper limit in TOSOH II PA. However, only 25% of 32 patients with BPH had PSA values below 2.3ng/ml. The mean serum PSA values in patients at each stage of prostatic cancer were higher than those in patients with BPH (p<0.01). In all of 5 patients with localized prostatic cancer, the serum PSA levels were more than 2.3ng/ml, while in one patient the serum PAP was higher than 1.6ng/ml, the normal upper limit in TOSOH II PAP.
We conclude that serum PSA values in TOSOH II PA are more sensitive in detecting localized prostatic cancer than serum PAP values and its sensitivity, specificity and efficacy to differentiate prostatic cancer from BPH are satisfactory. Further clinical studies with a larger series will be required to clarify the role of PSA in TOSOH II PA as a tumor marker in prostatic cancer.