PSA, free and free PSA (T376) [Back]
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| RISK ASSESSMENT VALUE: |
Free PSA in combination with Total PSA are utilized to calculate % Free PSA (fPSA). If the total PSA value lies in the 4-10 range, the % fPSA has a modest value in improving specificity. Those with benign disease have a wide range of fPSA values but those with prostate cancer cluster under 25% fPSA. Therefore, using a cut-off of under 25% fPSA allows one to pick up 95% of cancer and avoid 20% of benign disease. This may eliminate the need for adverse action in up to 20% of elevations in this range. Most of the cancer missed above 25% occurs in older individuals where the mortality ratio is small further improving its value. fPSA has less value in differentiating risk with total PSA below 4 or above 10 ng/ml
See total PSA and complexed PSA for additional discussion
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| NORMAL RESULTS: |
In the range of 4-10 ng/ml for total PSA, values for free PSA (fPSA) above 25% have a low risk for prostate cancer of mortality concern.
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| ABNORMAL RESULTS: |
Free PSA values < 25% are of little additional help in differentiating prostate cancer from benign disease relative to total PSA.
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| ADDITIONAL TESTS: |
None.
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| SAMPLE NEEDED: |
Separated serum from red or mottle stoppered tube.
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| SAMPLE STABILITY: |
PSA is stable when refrigerated for 48 hours, indefinitely when frozen. Avoid repeated freezing and thawing
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| METHOD & INSTRUMENT: |
Calculated from total and complex PSA values.
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| PURPOSE: |
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| PROFILE INCLUDES: |
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| RISK RANGE & UNITS: |
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