Key messages 

1. In NHSScotland, total prostate specific antigen (PSA) levels are measured as a first line test for men presenting in primary care with symptoms suggestive of prostate cancer.
2. Total PSA levels in whole blood or serum are more stable over time than free PSA levels.
3. Variation in total PSA levels in samples remained below 5% change from baseline for approximately 3 days at room temperature. Changes in free PSA levels exceeded 5% within about 24 hours, even at refrigerated temperatures. A 5% change from baseline is viewed as a clinically important change that affects the accuracy of the test result.
4. Refrigerating blood or serum samples for PSA testing slows down the changes in total and free PSA levels before testing.
5. Storing serum on the clot or allowing blood to coagulate leads to larger and faster changes in total and free PSA levels.
6. A requirement to test total PSA levels within 24 hours has potential implications for NHS Boards serving people living in remote, rural and island communities in Scotland.

Referred by

Clinical Lead for Cancer Performance and Earlier Diagnosis – Centre for Sustainable Delivery