free prostate Specific antigen/prostate specific antigen total in serum/plasma

^[1]^[2]

Indications

when serum PSA is > 4 ug/L (> 6 ug/L if > 65 years of age) & < 10 ug/L, serum free PSA/total PSA is useful for asessing risk of prostate cancer
if %free PSA is < 25%, then refer patient to urology for prostate biopsy, otherwise risk is low^[2]
with a total PSA 4-10 ng/mL, 95% of men with prostate cancer have free PSA < 25%, 20% of men with BPH have free PSA < 25%^[2]

↑ Loinc
↑ ^2.0 ^2.1 ^2.2 Catalona WJ, Partin AW, Slawin KM et al Use of the percentage of free prostate-specific antigen to enhance differentiation of prostate cancer from benign prostatic disease: a prospective multicenter clinical trial. JAMA. 1998 May 20;279(19):1542-7. PMID: https://www.ncbi.nlm.nih.gov/pubmed/9605898