Prostate-specific antigen

Prostate specific antigen, abbreviated PSA, is marker that is quite specific for the prostate.

General

• Quantity in the serum used to screen for prostate cancer.
• PSA immunostain useful for classifying a carcinoma as prostate carcinoma.

Serum PSA

• Normal - typically <= 4.0 ng/mL.
  • Sensitivity: 82% (whites), 90% (blacks).
  • Specificity: 52% (whites), 38% (blacks).).
• Increases with age.

Prostate specific antigen density

• Abbreviated PSAD.

Better predictor than (unadjusted) serum PSA for:

• Gleason score upgrading on prostatectomy.
• Benign prostate gland versus prostate cancer.

A forumla for PSAD

Benson et al.:

$PASD={\frac {serumPSA}{volume}}$

Where:

$volume={\frac {\pi }{6}}H\times W\times L$.

H, W, L are the height, width and length.

An alternate estimation of the volume is:

$volume={\frac {1}{2}}D1\times D2\times D3$.

D1, D2, D3 are the major axes.

Note:

• The volume of an ellipsoid is:

${\frac {4}{3}}\pi D1\times D1\times D3$.

See also

• Prostate cancer.