to PSA Testing
The PSA test measures prostate-specific antigen, a protein produced by prostate cells, in the blood. It serves as a screening tool to monitor prostate health. While a small amount of PSA is normal, elevated levels can suggest a prostate issue, though not necessarily cancer.
Identifying the Correct Blood Collection Tube
For prostate-specific antigen (PSA) testing, the blood sample is commonly collected in a serum separator tube (SST), which typically has a gold or “tiger top” stopper. Alternatively, a plain red-top tube can also be used. These tubes are chosen because PSA analysis requires serum, the liquid part of blood after clotting and separation from blood cells.
Serum separator tubes contain a gel barrier and a clot activator. The clot activator accelerates the blood’s natural clotting process. Once clotted, the gel barrier forms a stable separation between cellular components and serum during centrifugation. Plain red-top tubes contain a clot activator or no additive, allowing blood to clot naturally for serum separation. Proper tube use is important to ensure sample integrity and prevent hemolysis, which can interfere with PSA results.
Ensuring Accurate PSA Results: Pre-Collection Considerations
Several factors can temporarily influence PSA levels, potentially leading to misleading results. Ejaculation can elevate PSA levels, so avoid it for at least 48 hours before the test. Vigorous exercise, especially cycling due to prostate pressure, can also increase PSA levels; avoid such activities for 48 hours before the test.
Prostate examinations, like a digital rectal exam (DRE), can cause a temporary rise in PSA, so the blood draw should occur before a DRE. Recent medical procedures involving the prostate or urinary system, such as a prostate biopsy within the last six weeks, or a urinary tract infection, can elevate PSA levels. Inform your healthcare provider about all medications, as some drugs, like 5-alpha-reductase inhibitors, can lower PSA levels and affect results.
Handling the Blood Sample After Collection
After blood collection, specific handling steps maintain sample quality. For serum tubes, blood clots completely at room temperature within 20 to 30 minutes. Centrifugation of serum and plasma gel tubes is suggested within two hours.
Centrifugation separates serum from cellular components. In serum separator tubes, the gel barrier creates a distinct layer between serum and blood cells, ensuring clean separation. Once separated, transfer the serum to a labeled plastic transport tube. To maintain PSA stability, refrigerate the sample if not tested immediately, and transport it promptly to the laboratory. Samples for longer storage (over 24 hours) should be frozen at -70 degrees Celsius to minimize degradation.