FREE PSA (PROSTATE SPECIFIC ANTIGEN)
Why Is This Test Done?
Note:
1. Free PSA values regardless of levels should not be interpreted as absolute evidence for the presence or absence of disease. All values should be correlated with clinical findings and results of other investigations
2. False negative / positive results are observed in patients receiving mouse monoclonal antibodies for diagnosis or therapy
3. Free PSA levels may appear consistently elevated / depressed due to the interference by heterophilic antibodies & nonspecific protein binding
4. Immediate Free PSA testing following digital rectal examination, ejaculation, prostatic massage, ultrasonography and needle biopsy of prostate is not recommended as they falsely elevate levels
5. Hormone therapy affects Free PSA expression
Clinical Use · An aid in the early detection of Prostate cancer in males 50 years or older with Total PSA values between 4.0 and 10.0 ng/mL and nonsuspicious digital rectal examination. · An aid in discriminating between Prostate cancer and Benign Prostatic disease. Free PSA level is not used alone, but is mostly useful when expressed in a ratio with Total PSA. Hence PSA profile (Total + Free PSA) is the recommended test. Patients with benign conditions have a higher proportion of Free PSA compared with Prostate cancer
Interpretation
FREE PSA
0-0.5 ng/mL
FREE PSA
>0.5-2.5 ng/mL
FREE PSA
>2.5-5.0 ng/mL
FREE PSA
>5.0-10 ng/mL
FREE PSA
>10.0 ng/mL
Healthy males87.2%
12.8%
0%
0%
0%
BPH
51.9%
42.9%
4.2%
0.5%
0.5%
Stage A Prostate
Cancer
42.3%
11.5%
3.8%
3.8%
Stage B Prostate Cancer
23.9%
68.7%
7.5%
0%
0%
Preparation Instructions
Do not give sample within 7 days of Digital Rectal Examination (DRE) or Rectal Prostatic Ultrasonograp.
Preparation: No special preparation or fasting required, but avoid ejaculat