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Narrative Review: Aspirin Resistance and Its Clinical Implications

Simon Sanderson, DPH; Jon Emery, PhD; Trevor Baglin, MD; and Ann-Louise Kinmonth, MD
[+] Article, Author, and Disclosure Information

From University of Cambridge, Addenbrooke's Hospital, and Institute of Public Health, Cambridge, United Kingdom; and University of Western Australia, Claremont, Western Australia, Australia.

Potential Financial Conflicts of Interest: None disclosed.

Requests for Single Reprints: Simon Sanderson, DPH, University of Cambridge, Strangeways Research Laboratory, Wort's Causeway, Cambridge CB1 8RN, United Kingdom; e-mail, simon.sanderson@srl.cam.ac.uk.

Current Author Addresses: Dr. Sanderson: University of Cambridge, Strangeways Research Laboratory, Wort's Causeway, Cambridge CB1 8RN, United Kingdom.

Dr. Emery: University of Western Australia, 328 Stirling Highway, Claremont, Western Australia 6010, Australia.

Dr. Baglin: Clinical Haematology, Addenbrooke's National Health Service Trust, Addenbrooke's Hospital, Hills Road, Cambridge CB2 2QQ, United Kingdom.

Dr. Kinmonth: Department of Public Health and Primary Care, Institute of Public Health, Robinson Way, Cambridge CB2 2QQ, United Kingdom.

Ann Intern Med. 2005;142(5):370-380. doi:10.7326/0003-4819-142-5-200503010-00012
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Aspirin is currently the most cost-effective drug for the secondary prevention of cardiovascular disease, but treatment failures are relatively common. Several factors have been linked to these recurrent vascular events in patients prescribed aspirin, including smoking, drug interactions, nonadherence, comorbid conditions, and aspirin resistance. The term aspirin resistance has been used to describe not only an absence of the expected pharmacologic effects of aspirin on platelets but also poor clinical outcomes, such as recurrent vascular events, in patients treated with aspirin. Aspirin resistance is perhaps more precisely understood as the phenomenon of measurable, persisting platelet activation that occurs in patients prescribed a therapeutic dose of aspirin and may underlie an unknown proportion of aspirin treatment failures. Key challenges for future research are to standardize a definition of aspirin resistance and to compare whether different measures of platelet activation, either alone or in combination, independently predict cardiovascular events. These challenges must be met before researchers conduct studies to assess the clinical utility of testing on patient outcomes and cost-effective prescribing.


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Testing for Aspirin Resistance
Posted on March 21, 2005
Robert E Hoyt
Uniformed Services University of the Health Sciences
Conflict of Interest: None Declared

In the review by Sanderson et al on aspirin resistance they state that testing urine thromboxane B2 levels is both simple and inexpensive but they don't recommend routine biochemical testing.

It should be pointed out that the test is not inexpensive according to several reference laboratories. For example, the cost to perform the test by Quest Diagnostics (www.questdiagnostics.com) is $375. Cost should be added to the several limitations of this test of aspirin resistance.

Robert Hoyt MD Assistant Professor of Medicine and Family Practice Uniformed Services University of the Health Sciences

Simon Sanderson, Jon Emery, Trevor Baglin, and Ann-Louise Kinmonth Narrative Review: Aspirin Resistance and Its Clinical Implications Ann Intern Med 2005; 142: 370-380

Conflict of Interest:

None declared

Aspirin Resistance and Its Clinical Implications
Posted on April 11, 2005
Wai-Hong Chen
Department of Medicine, Queen Mary Hospital, The University of Hong Kong, Hong Kong, China
Conflict of Interest: None Declared

To the editor:

I read with interest the review entitled "Narrative Review: Aspirin Resistance and Its Clinical Implications" by Sanderson et al in the March 2005 issue of Annals of Internal Medicine. While I agree with the authors that it is important to understand and compare different measures of platelet activation in defining this term, I was surprised by the fact that one newer assay, VerifyNow Aspirin (Accumetrics, San Diego) was lumped in Table 2 with an older test the PFA-100, incorrectly described, and ignored in the body of the review.

Our group and others have been involved in clinical trials and published (1-3) on this instrument. We demonstrated that this system correlated to clinical outcomes (3), which is important to show for these laboratory measures of platelet function. In addition, there is an excellent comparative review of the strengths and weaknesses of this and various methods by Michelson in a recent issue of Circulation (4).

References 1. Wang JC, Aucoin-Barry D, Manuelian D, Monbouquette R, Reisman M, Gray W, Block PC, Block EH, Ladenheim M, Simon DI. Incidence of aspirin nonresponsiveness using the Ultegra Rapid Platelet Function Assay-ASA. Am J Cardiol. 2003;92:1492-4. 2. Coleman JL, Wang JC, Simon DI. Determination of Individual Response to Aspirin Therapy Using the Accumetrics Ultegra RPFA-ASA System. Point of Care 2004;3:77"“82. 3. Chen WH, Lee PY, Ng W, Tse HF, Lau CP. Aspirin resistance is associated with a high incidence of myonecrosis after non-urgent percutaneous coronary intervention despite clopidogrel pretreatment. J Am Coll Cardiol. 2004;43:1122-6. 4. Michaelson AD. Platelet function testing in cardiovascular diseases. Circulation 2004 Nov 9;110(19):e489-93.

Conflict of Interest:

None declared

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