[Different determination methods make interpretation of prostate-specific antigen more difficult]

The availability of numerous different assays for the determination of prostate-specific antigen (PSA) hs created substantial problems in the interpretation of PSA concentrations. Presently more than 40 assays are commercially promoted within the German market. The majority of the recently released assays claim the commonly used reference range (< 4 ng/ml) although this has no always been verified. Some companies entirely avoid the specification of reference ranges, others derive the data from very small cohorts. Reference ranges established with sera of young males or even with an unknown proportion of female sera are not valid in assessing the specificity of PSA assays to detect prostate cancer among male individuals between 50 and 80 years of age. Some companies recommend not to apply their assay for diagnostic purposes limit its use to the follow-up of patients previously diagnosed but to as having prostate cancer. This warning usually remains just as unknown to the urologist as the name of the assay used. Since PSA concentrations may vary in identical samples by a factor of 2, depending on the assay used, the clinician interpreting the results needs to be aware of the method applied and must have detailed information about the assay-specific reference range. Without this information, PSA loses its valuable diagnostic and prognostic features. Apart from avoidable worries on the patient's part, evidence of prostate cancer may be missed or unnecessary biopsies may be performed.