What Is an Aspirin Test?

An aspirin test is a diagnostic test to determine if a patient has aspirin resistance, meaning that the antiplatelet effects normally seen with aspirin are not present in that patient, or occur at a low level. This can be important for determining if a patient will benefit from aspirin therapy or, in the case of a patient already receiving therapy, to see if it is having a positive result. A doctor may recommend this test to get a complete picture of the patient's health, as patients on aspirin therapy who are not responding can be at an increased risk of health problems, and the only way to catch this early is with an aspirin test.

In the aspirin test, a doctor or nurse takes a sample of blood or urine from the patient. Some tests act quickly and allow the doctor to perform the test in the office, with results in a matter of minutes. Others may require sending a sample to the lab. The test determines whether aspirin has antiplatelet effects in the patient, and will also measure the strength of the reaction.

Doctors may prescribe aspirin therapy to reduce the risk of heart attack and stroke in patients for whom these may be concerns. In many people, aspirin reduces platelet formation, limiting blood clotting and increasing cardiovascular health. This can also come with some drawbacks, including an increased risk of internal bleeding and a greater chance of severe bleeding, even after minor cuts and scrapes. Platelets cannot respond as quickly to injuries in patients on aspirin therapy, and it is important to be aware of this risk before starting.

In some patients, a phenomenon known as aspirin resistance can occur. They may take the medication, but it will not have the same effects. Platelet counts will remain normal and their blood can still be prone to clotting and causing heart attacks and strokes. The purpose of the aspirin test is to check for this. If the patient doesn't respond well to aspirin, long-term therapy with the drug would not be productive and certainly will not have benefits for the patient. It can also put the patient at risk, as he may mistakenly believe that he is lowering his risks, when he is actually still at risk of potentially serious complications.

Doctors may also run tests to check for allergies if they believe patients are allergic to aspirin. In this type of aspirin test, the goal is to measure reactivity to see if patients should not take aspirin at all to avoid the risk of severe allergic reactions.