The newest aspirin dispute: What can we learnin orthopedics?

Issue: June 2006

Douglas W. Jackson [photo] --- Douglas W. Jackson, Chief Medical Editor

It is always easier to take a look at how an issue plays out in other specialties in order to gain some insight into how related aspects might apply to us in orthopedics. That leads us to another controversy questioning the effectiveness of aspirin — one of the most common over-the-counter medications — in reducing the recurrence of heart attacks and strokes in the general population.

The basic concept in the controversy: “aspirin resistance” (aspirin failing to achieve its anti-clotting effects in certain individuals), and the topic has been discussed increasingly over the past four years. It calls into question the uniform use of ASA in specific high-risk populations.

Deciding without the facts

If aspirin resistance does exist, then “resistant” patients who receive aspirin therapy may not benefit from its desired anti-clotting effects. From the few articles I have read on this topic and from listening to different experts, it appears such resistance occurs in somewhere between 0% to as high as 30% of the general population.

There is a need for some definitive work in this controversial area that answers the following questions:

Does aspirin resistance exist?
If so, what is the incidence and how do you best identify these individuals?
Does the current proposed urine test (marker) help identify resistant patients?
What is the treatment for aspirin resistant patients (do they need higher doses of aspirin, other oral medications or both)?

It continues to amaze me how many people prophylactically take a baby aspirin — 81 mg/day — feeling it will help reduce their chances or the consequences of having a heart attack or stroke.

This use is based on the American Heart Association recommending the low doses for those who have had heart attacks or strokes, where it has been shown to reduce repeat episodes, and for certain other high-risk individuals. The potential for aspirin therapy to decrease the negative clotting effects, while also being inexpensive and easy to use, makes it very appealing to physicians and patients.

Questions of financial motives

As the issue of “aspirin resistance” has been debated in cardiology, internal medicine and neurology, several points of discussion have emerged that have relevance to our field. It is worth noting that experts on both sides of the “aspirin resistance” controversy either support or refute the specific studies that have been published and presented. Individuals also have raised questions related to the influence of the drug company funding of these studies and comparisons. Drug companies often fund studies in order to acquire data that will support the introduction of a more expensive or an alternative drug to aspirin. Those on opposing sides of the controversy often question the financial incentives and funding of the various investigators and experts in the field. Their questions often relate to consulting fees and other direct and indirect benefits to the investigators. It is now often difficult to find an expert who has in-depth knowledge of the specific science and can educate other physicians, and whose findings are not also challenged by critics on the basis of motivation and incentives.

This issue of legitimacy is one major divide. A second major divide in this whole discussion involves treating physicians’ incentives. Some physicians are ordering a controversial urine test to identify aspirin resistance in all of their patients under consideration for aspirin therapy. Yet many feel the current urine marker does not identify these resistant patients, while others, a group that often includes the treating physician, feel strongly it is the right one. There have been some criticisms that physicians using this test extensively may benefit financially from ordering this laboratory test.

The art of medicine

There is a strong desire to have reliable markers that would identify patients resistant to a specific drug and allow physicians to individualize treatment. We all want to give our patients the best treatments, but the science is often not strong enough to show that what we recommend is unequivocally effective. In this aspirin controversy, some say there is no aspirin resistance and the urine test is not valid. For now it gets down to believers and nonbelievers — a far cry from anything approaching evidence-based medicine — and whenever this situation occurs in medicine, incentives and motivations come into question.

The Pharma lightning rod

Such criticism intensifies when drug companies bring alternative treatments and tests to the marketplace, particularly when a new drug costs more. It is even a greater challenge when we lack the natural history of the underlying risk-to-benefit treatment ratios.

Dr. Paul Lotke shares his insight into the studies that we need in orthopedics to further clarify regarding the controversies of prophylactic use of anti-coagulation agents and treatments (see page 38).

Now we are left with one more issue (aspirin-resistance) to consider in orthopedics without clear-cut answers. This controversy probably does not impact your patient treatment recommendations right now, but it may in the future as more evidence comes to light.

We will have to critique each new study from many different angles and, hopefully, we can base decisions on the facts, and not approach them as believers or non-believers in the validity of the motivations for the studies.