Platform
Company
Electrolytes
Review status
Currently under review
Pending specialist review and validation.
This test evaluates how your platelets clump together in response to ristocetin, a reagent that engages the bond between a protein in your blood called von Willebrand factor and a receptor on the platelet surface. The laboratory uses optical aggregometry, a method that measures changes in light passing through platelet-rich plasma as platelets clump.
It helps assess the function of the platelet glycoprotein Ib receptor and the interaction with von Willebrand factor. Doctors use it alongside other platelet function and von Willebrand factor tests to investigate easy bruising, nosebleeds, heavy periods, or bleeding after procedures.
Results can point toward specific conditions that affect platelet function or von Willebrand factor, such as certain subtypes of von Willebrand disease, platelet-type von Willebrand disease, or Bernard–Soulier syndrome. Identifying the right cause matters because treatments differ and some therapies can worsen bleeding in particular disorders.
Your clinician may order this test if you have mucocutaneous bleeding symptoms, an abnormal screening platelet function result, a family history suggesting an inherited platelet disorder, or to help plan surgery or dental work. It is typically interpreted together with von Willebrand factor antigen and activity, platelet counts, and other specialized studies.
A typical response suggests the interaction between von Willebrand factor and the platelet receptor is working as expected. A reduced or absent response can suggest a problem with that interaction or with the platelet receptor itself, while an exaggerated response can point toward certain von Willebrand factor variants. Your care team will consider your symptoms, blood counts, and companion von Willebrand factor tests to decide what the pattern means for you.
If results are unexpected or borderline, your clinician may repeat testing under controlled conditions or add follow-up studies such as von Willebrand factor multimer analysis, genetic testing, or additional platelet function assays. Do not start or stop any medicines on your own; discuss next steps and any bleeding precautions with your clinician.
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.
Aspirin, NSAIDs, clopidogrel and related antiplatelet drugs, many antidepressants such as SSRIs, and some herbal supplements like fish oil or ginkgo can blunt or alter platelet responses. Tell your care team about all medicines and supplements before testing.
Platelet function is time sensitive. The blood must be processed promptly to prepare platelet-rich plasma and tested under controlled conditions. Delays, temperature extremes, vibration, or a clotted sample can give misleading results.
Acute illness, inflammation, vigorous exercise, and emotional stress can change von Willebrand factor levels and platelet behavior. These conditions may temporarily alter results, so your clinician may recommend testing when you are well.
Recent alcohol intake, large doses of caffeine, and some foods or supplements can influence platelet reactivity. Follow any pretest instructions from the laboratory regarding fasting and avoidance of certain substances.
Very low platelet counts, giant platelets, or anemia can affect optical measurements and aggregation curves. Your blood count and smear are reviewed to ensure the test is interpretable.
Recent transfusion of platelets or plasma and pregnancy can change von Willebrand factor levels and the test pattern. Let your clinician and the lab know about recent transfusions and whether you are pregnant.
References