Serum Levels
PSA is normally present in the blood at very low levels. The reference range of less than 4 ng/mL for the first commercial PSA test, the Hybritech Tandem-R PSA test released in February 1986, was based on a study that found 99% of 472 apparently healthy men had a total PSA level below 4 ng/mL—the upper limit of normal is much less than 4 ng/mL.
Increased levels of PSA may suggest the presence of prostate cancer. However, prostate cancer can also be present in the complete absence of an elevated PSA level, in which case the test result would be a false negative.
Obesity has been reported to reduce serum PSA levels. Delayed early detection may partially explain worse outcomes in obese men with early prostate cancer. After treatment, higher BMI also correlates to higher risk of recurrence.
PSA levels can be also increased by prostatitis, irritation, benign prostatic hyperplasia (BPH), and recent ejaculation, producing a false positive result. Digital rectal examination (DRE) has been shown in several studies to produce an increase in PSA. However, the effect is clinically insignificant, since DRE causes the most substantial increases in patients with PSA levels already elevated over 4.0 ng/mL.
The "normal" reference ranges for prostate-specific antigen increase with age, as do the usual ranges in cancer:
| Age | <50 | 50 - 59 | 60 - 69 | >70 | (years) | ||||
|---|---|---|---|---|---|---|---|---|---|
| Cancer | No cancer | Cancer | No cancer | Cancer | No cancer | Cancer | No cancer | ||
| 5th percentile | 0.4 | 0.3 | 1.2 | 0.3 | 1.7 | 0.3 | 2.3 | 0.4 | (ng/mL) |
| 95th percentile | 163.0 | 2.5 | 372.5 | 4.7 | 253.2 | 8.3 | 613.2 | 17.8 | |
Read more about this topic: Prostate-specific Antigen
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