Prostate-specific antigen is an immunological term used when examining the prostate gland and is the most sensitive tumor marker for prostate cancer. It is a good guide for the screening, diagnosis, staging and treatment of prostate cancer. 1. Definition: Prostate-specific antigen, PSA for short, is produced by endoplasmic vesicles and is present in the prostate epithelial cells. The normal prostate tissue contains PSA. 2, abnormal results: the normal condition of the test results <4ng/L, the presence of total PSA and free PSA in the serum. elevated PSA can be caused by urinary tract obstruction, prostatitis, prostate hyperplasia and prostate cancer, if the value continues to rise, and after ruling out the possibility of benign disease, then the possibility of prostate cancer should be considered. 3.Checking precautions: control your diet and don't drink excessively before blood sampling. It is not necessary to take blood on an empty stomach, keep a relaxed mood and avoid overexertion. Avoid sexual life for 3-7 days before the test. If there are operations or examinations such as rectal examinations, catheterization, cystoscopy, etc., it may also affect the value of PSA. After the test, apply pressure at the site of blood draw for 3 minutes. If you show signs of dizziness, rest flat on your back and drink some plain water. If there is local bruising, you can apply a wet compress with hot towels a day later. For total prostate-specific antigen, it is a clinically important immunological test that is systematically treated according to the test results.