The full name of PSA is prostate-specific antigen, which is a proteolytic enzyme produced mainly by prostate epithelial cells and is normally secreted into prostatic fluid or semen in the active free form (f-PSA), while PSA in serum exists mainly in the bound form, usually the sum of f-PSA and bound PSA, i.e. total PSA (t-PSA), represents total serum PSA. levels. Serum PSA measurement is highly accurate, stable, reproducible, and non-invasive, and is useful for early diagnosis of prostate cancer, monitoring treatment response and determining prognosis. It can also be used for the screening of prostate cancer in high-risk groups (men over 50 years old). PSA is a prostate-specific antigen, but not a specific antigen for prostate cancer, and both normal and BPH prostate epithelium can secrete PSA. The normal range of PSA is 0-4ng/ml, but as the prostate itself increases in size with age, the serum PSA will rise accordingly. Clinically, it is often necessary to adjust the normal PSA value according to the patient’s age. The reference values (Tandcm-R method) are 40-49 years old: 0-2.5ng/ml; 50-59 years old: 0-3.5ng/ml; 60-69 years old: 0-4.5ng/ml; 70-79 years old: 0-6.5ng/ml. Statistical data found that the false positive rate of PSA test is as high as 30%. In other words, 1/3 of men with abnormal PSA test findings do not have prostate cancer at all. This is because serum PSA can also be elevated in the following situations: prostatitis, urinary retention, intense rectal examinations, prostate trauma, prostate biopsy, and this elevation can last up to 6 weeks. Sexual activity can also raise PSA levels, mainly because the contractile activity of the prostate during orgasm will cause a large amount of synthesized PSA to enter the bloodstream. Therefore, the patient should not have sex for at least two days prior to the PSA test. In addition, continuous use of 5α-reductase inhibitors (e.g., Prolotherapy) for more than 6 months can reduce serum PSA levels by about 50%. The above factors should be excluded when determining the clinical significance of serum PSA. If the serum PSA is elevated except for the above mentioned reasons, PSA at 4-10ng/ml needs to be combined with PSA and other indicators of prostate imaging to determine whether to follow up and observe or to perform prostate puncture biopsy; if PSA ≥10ng/ml, then prostate puncture biopsy is necessary. Therefore, a comprehensive and detailed analysis of the PSA results is needed to exclude the influence of other factors on the test results in order to make an accurate and comprehensive diagnosis.