Its principal physiological function is to manufacture the fluid that nurtures spermatozoa. What happens to one of its principle prostate-specific proteins in serum upon ejaculation might seem a sensible first step in sorting out the use of a serum test. Given that PSA is often measured, that thousands of papers are published on PSA each year, and millions of tests done, one might think that the effects of basic physiological changes would be well sorted out. When an assay is just a guess To answer the question about the effect on PSA of ejaculation, it is necessary to enter the arcane world of immunoassays and their properties.
Any assay is designed to measure something within certain concentration limits.
Many of the articles examine populations with very low PSA levels. But where prostate cancer is just a suspicion a serum PSA might well be part of the diagnostic regimen in a man who is sexually active. Knowing whether and how ejaculation affects serum PSA will be important. That will affect the interpretation and usefulness of the test. Many articles look only at young men, and at times early after ejaculation.