PSA Test: Prostate-Specific Antigen Numbers, Age Adjustments and What to Do Next

PSA is a protein made by prostate cells — both healthy and cancerous. It liquefies semen and is detectable in blood in tiny quantities. When the prostate enlarges (benign prostatic hyperplasia), inflames (prostatitis), or develops cancer, PSA release goes up. Because all three conditions raise PSA, an elevated result identifies "something is going on with the prostate" — not specifically cancer.

PSA is also raised by mechanical stimulation of the prostate (digital rectal examination, cycling, prolonged sitting, ejaculation) and by anything that inflames the urinary tract (recent UTI, catheterisation). These effects can double or triple the PSA transiently. A first-ever elevated PSA is always repeated 2–6 weeks later after avoiding these triggers.

When PSA sits above the age threshold, three "refiners" reduce false positives before any biopsy. Free-to-total PSA ratio: PSA circulates in bound and free forms — cancer cells tend to release more bound PSA, so a lower free ratio (< 0.15) raises cancer probability. PSA density (PSA divided by prostate volume on MRI): densities above 0.15 ng/mL/cc raise suspicion; below 0.10 usually favours benign hyperplasia. PSA velocity: a rise > 0.75 ng/mL per year (or 0.35 in younger men) matters more than a static borderline value.

The biggest change in the past decade is the routine use of multi-parametric MRI BEFORE biopsy. The PRECISION trial (2018) and follow-up MRI-first pathways show MRI can avoid up to 30% of biopsies while catching clinically significant cancers earlier. PI-RADS scoring on MRI (1–5) directs targeted biopsy only to areas that look suspicious.

PSA screening is genuinely nuanced. The European ERSPC trial (long-term follow-up) shows PSA screening reduces prostate-cancer mortality by roughly 20–30% over 16 years. The US PLCO trial did not show a benefit — likely because most of the control arm was also screened outside the trial. The trade-off is overdiagnosis: many detected cancers would never have caused harm in a man’s lifetime, but the label triggers treatment (surgery, radiation) with real side-effects (incontinence, erectile dysfunction).

Current guidelines (USPSTF, EAU, NICE) recommend a shared decision-making conversation for men aged 50–69 (or 45+ if family history or Black ethnicity). The conversation includes the modest mortality reduction, the risk of overdiagnosis, and the modern MRI-first pathway that mitigates unnecessary biopsy.