[Diagnostic and prognostic value of serum prostate specific antigen in prostate carcinoma].
The upper normal limit of serum prostate specific antigen (PSA) of 4 ng/ml is positively evaluated since it discriminates a large percentage of patients having prostate cancer. The PSA limit of 2.5 ng/ml may be used accordingly for patients younger than 50 years of age. The PSA range of 3.3-4 ng/ml may indicate a percentage of patients positive for prostate carcinoma. The PSA above 10 ng/ml indicates that patients have prostate carcinoma by more than 50 %, which is more than double as compared to patients having PSA limits between 4.1-10 ng/ml. It is important to repeat doubtful PSA tests after 3-4 months. If within a year an increase in PSA of more than 2 ng/ml is detected, a high risk of death from prostate cancer is expected. The time for doubling PSA values within a year is described as "velocity index". As for free PSA, this test is not often applied in many nuclear medicine centers. According to the Mayo Clinic, USA, instructions, when total PSA is 2-3.9 ng/ml and free PSA above 18% of these values, the possibility of prostate cancer is less than 10%. On the contrary, for the above total PSA values, if free PSA is less than 10% of these values, the possibility of prostate cancer increases to more than 30%. It is suggested that PSA values be expressed per g of prostate tissue in order to relate to prostate volume. However, one should have in mind that prostate carcinomas have less PSA per g than hyperthophic glands and their volume is usually larger. There are cases where treatment of prostate hypertrophy with finasteride or treatment of prostate cancer with anticancer drugs, may induce a false low PSA. More information about the practical importance of PSA values is expected after 2 or 3 years when a study by the National Cancer Institute of USA on 74,000 men will be completed.
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