Prostate-Specific Antigen (PSA), Total and Free, Serum
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
The percentage of measured prostate-specific antigen (PSA) existing in the free form (free:total PSA ratio) is useful in assessing the risk of prostate cancer in patients with borderline or moderately increased total PSA (4.0-10.0 ng/mL) and has been used to help select men who should have follow-up prostate biopsy.
Most prostate cancers are slow growing, so the utility of prostate cancer screening is marginal in most men with a life expectancy of <10 years.
Electrochemiluminescent Immunoassay (ECLIA)
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
PSA Total and Free, S
PSA (Prostate-Specific Antigen)
PSA Free/Total Ratio
PSA Total and Free
PSA (Prostate-Specific Antigen)
PSA Free/Total Ratio
PSA Total and Free
Specimen Type Describes the specimen type needed for testing
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
Preferred: Red top
Acceptable: Serum gel
Submission Container/Tube: Plastic vial
Specimen Volume: 1 mL
Collection Instructions: Spin down within 3 hours of draw and separate serum from cells.
1. Free PSA can only be added on within 12 hours of performing total PSA. Specimen must have been shipped frozen.
2. Include patient’s age.
Specimen Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
Mild OK; Gross reject
Mild OK; Gross OK
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Prostate-specific antigen (PSA) is a glycoprotein that is produced by the prostate gland, the lining of the urethra, and the bulbourethral gland. Normally, very little PSA is secreted in the blood. Increases in glandular size and tissue damage caused by benign prostatic hypertrophy, prostatitis, or prostate cancer may increase circulating PSA levels.
PSA exists in serum in multiple forms: complexed to alpha-1-anti-chymotrypsin (PSA-ACT complex), unbound (free PSA), and enveloped by alpha-2-macroglobulin (not detected by immunoassays).
Higher total PSA levels and lower percentages of free PSA are associated with higher risks of prostate cancer.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
PSA Upper Limit (ng/mL)
< or =2.0
< or =2.5
< or =3.5
< or =4.5
< or =6.5
> or =80
< or =7.2
Females: not applicable
Males: When total PSA is in the range of 4.0-10.0 ng/mL, a free:total PSA ratio < or =0.10 indicates 49% to 65% risk of prostate cancer depending on age; a free:total PSA ratio >0.25 indicates a 9% to 16% risk of prostate cancer, depending on age.
Females: not applicable
When total prostate-specific antigen (PSA) concentration is <2.0 ng/mL, the probability of prostate cancer in asymptomatic men is low, further testing and free PSA may provide little additional information. When total PSA concentration is >10.0 ng/mL, the probability of cancer is high and prostate biopsy is generally recommended.
The total PSA range of 4.0 to 10.0 ng/mL has been described as a diagnostic "gray zone," in which the free:total PSA ratio helps to determine the relative risk of prostate cancer (see table below). Therefore, some urologists recommend using the free:total ratio to help select which men should undergo biopsy. However even a negative result of prostate biopsy does not rule-out prostate cancer. Up to 20% of men with negative biopsy results have subsequently been found to have cancer.
Based on free:total PSA ratio: the percent probability of finding prostate cancer on a needle biopsy by age in years:
Free:total PSA ratio
> or =70 years
< or =0.10
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Normal results do not eliminate the possibility of prostate cancer.
Values obtained with different assay methods or kits may be different and cannot be used interchangeably.
Tumor markers are not specific for malignancy. Test results cannot be interpreted as absolute evidence for the presence or absence of malignant disease.
Specimens drawn from patients undergoing prostate manipulation, especially needle biopsy and transurethral resection, may show erroneously high prostate-specific antigen (PSA) results. Care should be taken that specimens are drawn before these procedures are performed.
Prostate cancer patients receiving treatment with antiandrogens and luteinizing hormone-releasing factor agonists may exhibit markedly decreased levels of PSA. Also, men treated for benign prostatic hyperplasia with inhibitors of 5-alpha-reductase (finasteride) may demonstrate a significant reduction in PSA levels compared to values before treatment. Care should be taken in interpreting values for these individuals.
In patients receiving therapy with high biotin doses (ie, >5 mg/day), no sample should be taken until at least 8 hours after the last biotin administration.
In rare cases, interference due to extremely high titers of antibodies to ruthenium or streptavidin can occur.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Oesterling JE, Jacobsen SJ, Chute CG, et al: Serum prostate-specific antigen in a community-based population of healthy men. JAMA 1993 Aug 18;270:860-864
2. Catalona WJ, Smith DS, Wolfert RL, et al: Evaluation of percentage of free serum prostate-specific antigen to improve specificity of prostate cancer screening. JAMA 1995:274(15);214-1220
3. Jacobsen SJ, Bergstralh EJ, Guess HA, et al: Predictive properties of serum prostate-specific antigen testing in a community-based setting. Arch Intern Med 1996;156:2462-2468
4. Oesterling JE, Jacobsen SJ, Klee GG, et al: Free, complexed and total serum prostate specific antigen: the establishment of appropriate reference ranges for their concentrations and ratios. J Urol 1995;154:1090-1095
5. Dworschack RT, Thiel RP, Picolli SP: Clinical evaluation of the free/total PSA ratio generated with the Elecsys Total and Free PSA assays on the Elecsys 1010 and 2010 systems. Clin Chem 2001 Jun; 47 (6 Suppl S):A149. (Abstract)
Method Description Describes how the test is performed and provides a method-specific reference
Total prostate-specific antigen (PSA):
Instrument used is Roche Cobas 6000 e601. The Roche Elecsys Total PSA method is a sandwich electrochemiluminescent immunoassay that employs a biotinylated monoclonal PSA-specific antibody and a monoclonal PSA-specific antibody labeled with ruthenium complex. PSA in the specimen reacts with both the biotinylated monoclonal PSA-specific antibody (mouse) and the monoclonal PSA-specific antibody (mouse) labeled with a ruthenium, forming a sandwich complex. Streptavidin-coated microparticles are added and the mixture is aspirated into the measuring cell where the microparticles are magnetically captured onto the surface of the electrode. Unbound substances are then removed with ProCell. Application of voltage to the electrode induces the chemiluminescent emission, which is then measured against a calibration curve to determine the amount of PSA in the patient specimen. This method has been standardized against the Reference Standard/WHO 96/670.(Package insert: Roche total PSA reagent, 07-2010. Roche Diagnostic Corp., Indianapolis, IN)
Instrument used is Roche Cobas 6000 e601. The Roche Elecsys Free PSA method is a sandwich electrochemiluminescent immunoassay that employs a biotinylated monoclonal PSA-specific antibody and a monoclonal PSA-specific antibody labeled with ruthenium complex. Free PSA in the specimen reacts with both the biotinylated monoclonal PSA-specific antibody (mouse) and the monoclonal PSA-specific antibody (mouse) labeled with a ruthenium, forming a sandwich complex. Streptavidin-coated microparticles are added and the mixture is aspirated into the measuring cell where the microparticles are magnetically captured onto the surface of the electrode. Unbound substances are then removed with ProCell. Application of voltage to the electrode induces the chemiluminescent emission, which is then measured against a calibration curve to determine the amount of free PSA in the patient specimen. This method has been standardized against the Reference Standard/WHO 96/668.(Package insert: Roche free PSA reagent, (2012-2 V5). Roche Diagnostic Corp., Indianapolis, IN)
The free PSA concentration is divided by the total PSA to derive the free:total ratio. The PSA, total and free test provides a free PSA measurement on every specimen, however, because very high or low total PSA measurements are predictive in themselves, a ratio is provided only when the total PSA is in the range of 4.0 to 10.0 ng/mL.
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Monday through Friday; 5 a.m.-12 a.m., Saturday; 6 a.m.-6 p.m.
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location The location of the laboratory that performs the test
Test Classification Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer's instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR), Investigation Use Only (IUO) product, or a Research Use Only (RUO) product.
This test has been cleared or approved by the U.S. Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.
CPT Code Information Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
|Result ID||Reporting Name||LOINC Code|
|PSA_R||Free PSA/PSA Ratio||12841-3|