Platelet Aggregation Test

General Information

A 'normal control' must be collected from a willing, consenting donor as soon as possible after collection of patient samples. All requests for Platelet Aggregation testing must be accompanied by a patient questionnaire (click Here). Please complete all information fully 

Samples that meet the following criteria will not be processed:

• Haemolysed, clotted, underfilled or overfilled samples.
• Samples >4 hours old from the time of collection.
• Samples from patients who have taken aspirin/aspirin-containing medicines/NSAIDs. Re-collection of samples should occur 10-14 days after cessation of drugs that interfere with normal platelet function.
• Samples from patients who have just received platelet transfusions (1-2 days) prior to test request.
• Samples which fail the minimum data set

Assay Limitations:

• If the patient is taking any drugs, these may give falsely reduced results (not just aspirin). Some dietary products have also been implicated. This is the reason that all patients are asked the pre-analytical questionnaire. If the patient has taken any of the drugs listed in the first four rows, reschedule the test. With the items in the rows below the test can still go ahead, but this data can be used on the report should any anomalies in the aggregation occur.
• When checking the PRP make sure the RBC is <0.5 x 10¹²/L and the WBC is <0.5 x 10⁹/L.
• Cryoglobulins may cause transmission changes similar to spontaneous aggregation. Warming PRP and PPP should remove this risk.
• Aggregation should be performed within three hours of the blood being taken. Always cap the tubes in any case.
• Patients who have ingested aspirin containing drugs are normally excluded from platelet function tests for 10 - 11 days after aspirin ingestion. Aspirin interferes with thromboxane A2 (TxA2) production from prostaglandins in platelets. TxA2 is a potent physiological activator of platelets.
• Poor venepuncture i.e. activated blood samples. This can manifest as a haemolysed sample, spontaneous aggregation or over reactive response to low concentration agonists. Sample should be rejected and retaken.