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Company
Immunology & Autoimmune
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Currently under review
Pending specialist review and validation.
This test measures how quickly a small opening in a special membrane closes when your blood flows through it in a laboratory device called a platelet function analyzer. The cartridge used contains collagen and epinephrine, which stimulate platelets to stick and form a plug. The result reflects the performance of platelets and von Willebrand factor in the first step of stopping bleeding, known as primary hemostasis.
It is performed on citrated whole blood and provides a rapid, global screen of platelet-related function. Because it is an in vitro method, it avoids a skin incision and offers a standardized way to assess how platelets respond to activation under controlled flow.
Your clinician may order this test if you have easy bruising, frequent nosebleeds, heavy menstrual bleeding, or unexpected bleeding during or after procedures. It helps screen for problems with platelet function or von Willebrand factor, and it can show the impact of medications that impair platelets, such as aspirin or some anti-inflammatory drugs.
The result can guide decisions about perioperative planning, the need for additional specialized testing, or changes to medications. It is a screening tool, so it is interpreted together with your history, a physical exam, a blood count, and, when indicated, further platelet or von Willebrand evaluations.
A longer closure time generally suggests that platelets are not forming an effective plug under test conditions, which can occur with von Willebrand disease, inherited or acquired platelet function disorders, or the effect of certain medications. Shorter times are typically not concerning. Because many factors can influence the result, a single abnormal value may be repeated, ideally when you are off interfering medicines and when you are well hydrated.
If your result is outside the expected range, your clinician may review your medication list, repeat testing, and consider more specific studies, such as von Willebrand factor assays or platelet aggregation testing. The result is one piece of the overall picture and is best interpreted alongside your symptoms, blood counts, and planned procedures.
Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.
Medicines like aspirin and many anti-inflammatory drugs reduce platelet function and commonly prolong the epinephrine cartridge result. Tell your clinician about all prescription and over-the-counter medicines.
Low platelet count or low red blood cell concentration can prolong the result by altering flow and platelet interactions. A complete blood count is usually considered when interpreting the test.
Improper tube fill, delays to testing, temperature extremes, or vigorous shaking can affect platelet behavior and change the closure time. Proper collection and prompt analysis help ensure reliable results.
Lower von Willebrand factor, whether inherited or due to stress, illness, or blood type differences, can influence the result. Additional assays may be needed to confirm the cause.
Selective serotonin reuptake inhibitors, some antibiotics, herbal supplements, and alcohol can affect platelet function. Provide a full list of supplements and substances you use.
Fever, recent exercise, or acute phase reactions can transiently change platelet reactivity, sometimes normalizing or prolonging results. Retesting when you are well may be appropriate.
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