What does the Prostatic Acid Phosphatase test measure?

Why is Prostatic Acid Phosphatase measured?

PAP was the first widely used tumour marker for prostate cancer and remains valuable in specific contexts despite being largely supplanted by PSA for screening and early detection. It retains clinical utility in advanced disease, particularly metastatic castration-resistant prostate cancer, where rising PAP can indicate progression when PSA is suppressed by androgen-deprivation therapy. PAP is also a forensic marker in sexual-assault investigations and occasionally rises with prostatic manipulation or benign prostatic disease.

Reference ranges

Standard reference

Approximately 0–3.5 ng/mL, assay-specific.

Functional medicine optimal

There is no 'optimal' level for a tumour marker; lower is generally better, with trending more informative than isolated values. Very low or undetectable PAP is typical in healthy men.

Units

ng/mL, µg/L

Reference ranges vary by laboratory and assay platform. Interpret in context of the issuing laboratory's stated range.