PSA density

The PSA density (PSAD), is a calculation performed at diagnosis and is the serum prostate specific antigen (PSA) level (ng/mL) divided by the volume of the prostate gland (mL), resulting in a value with the units, ng/mL^2 1. Prostate volume is calculated from TRUS measurements ^2,3. 

Alternatively, PSA density may be calculated using MRI measurements of prostate volumes or less commonly, using postsurgical histopathological measurements of prostate volumes ^3,4.

PSA density has been used as a prognostication tool in helping decide between an active surveillance or an invasive approach when managing prostate carcinoma ⁵. The cut-off used most commonly is 0.15 or 0.20 ng/mL². 

Practical points

Recent studies have shown that the most widely used thresholds have low detection rate, as threshold of 0.10 and 0.15 ng/mL² resulted in the detection of only 77 and 49% of clinically significant (Gleason score ≥ 7) prostate cancers ⁶. 

Another recent study proposed stratification based on prior biopsy history for patients with elevated PSA level (>4 ng/mL) ⁷: 

• no prior prostate biopsy: <0.10 ng/mL²
• prior negative biopsy: <0.15 ng/mL²

See also

• prostate specific antigen (PSA)
• PSA velocity
• free/total PSA ratio