ARUP's Laboratory Test Directory

Prostate Specific Antigen, Free Percentage (Includes Free PSA and Total PSA) : 0080206

Mnemonic: PSA FP

Ordering Recommendation: Do not use for initial prostate cancer screening; preferred test is total prostate specific antigen (PSA) (0070121) in conjunction with digital rectal exam (DRE). May be useful in distinguishing benign conditions from cancer in patients with mildly elevated total PSA and negative DRE.
Methodology: Quantitative Electrochemiluminescent Immunoassay
Performed: Sun-Sat
Reported: Within 24 hours
Specimen Required: Collect: Serum separator tube or plasma separator tube. Also acceptable: Plain red, green (sodium or lithium heparin), lavender (EDTA), or pink (K2EDTA).

Specimen Preparation: Allow specimen to clot completely at room temperature. Separate serum or plasma from cells ASAP or within 2 hours of collection. Transfer 1 mL serum or plasma to an ARUP Standard Transport Tube. (Min: 0.5 mL)

Storage/Transport Temperature: Frozen.

Unacceptable Conditions: Grossly hemolyzed specimens. Vaginal washings.

Stability (collection to initiation of testing): After separation from cells: Ambient: 8 hours; Refrigerated: 48 hours; Frozen: 3 months
Reference Interval:
By report
Results include: PSA-Free, PSA, PSA-Percent Free
Interpretive Data: The Roche PSA electrochemiluminescent immunoassay is used. Results obtained with different assay methods or kits cannot be used interchangeably. The Roche PSA method is approved for use as an aid in the detection of prostate cancer when used in conjunction with a digital rectal exam in men age 50 and older. The Roche Modular E170 PSA method is also indicated for the serial measurement of PSA to aid in the prognosis and management of prostate cancer patients.  Elevated PSA concentrations can only suggest the presence of prostate cancer until biopsy is performed. PSA concentrations can also be elevated in benign prostatic hyperplasia or inflammatory conditions of the prostate. PSA is generally not elevated in healthy men or men with non-prostatic carcinoma.
                                                                                   
ARUP uses the Roche Free PSA electrochemiluminescent immunoassay method in conjunction with the Roche PSA electrochemiluminescent immunoassay method to determine the free PSA percentage. The free PSA percentage is an aid in distinguishing prostate cancer from benign prostatic conditions in men age 50 and older with a total PSA between 3 and 10 ng/mL and negative digital rectal examination findings. Prostatic biopsy is required for the diagnosis of cancer. (Refer to: JAMA 1998; 279: 1542-1547)                                                                                                             
                                                                                           
 
In patients with total PSA concentrations of 4-10 ng/mL, the probability of finding prostate cancer on needle biopsy by age in years is:
% Free PSA 50-59 years 60-69 years 70 years and older
0-10% 49% 58% 65%
11-18% 27% 34% 41%
19-25% 18% 24% 30%
> 25 % 9% 12% 16%
Other factors may help determine the actual risk of prostate cancer in individual patients.

Note: The free percentage is calculated using the total and free PSA results.
CPT Code(s): 84153; 84154
Cross References: Free Prostate Specific Antigen (Prostate Specific Antigen, Free Percentage (Includes Free PSA & Total PSA) , PSA, Free (Prostate Specific Antigen, Free Percentage (Includes Free PSA & Total PSA))