How to measure or mend adherence a big unknown
How to measure or mend adherence a big unknown
Data suggest only about two-thirds compliant
About 60% of AIDS patients on new combination therapies are taking 80% or more of their medications, says Terry Blaschke, MD, chief of the division of clinical pharmacology and professor of medicine and molecular pharmacology at Stanford University in Palo Alto, CA.
That’s Blaschke’s best guess, based on what researchers at Johns Hopkins University found when they looked at 202 AIDS patients, some taking the older antiretrovirals and some taking a combination therapy that included a protease inhibitor.1
Though most of the subjects at Johns Hopkins were African-American men, the results would have been much the same if the subjects had been white, well-educated, and middle-class, other experts on the subject say.
"Some of what we’d call the smartest and best-educated AIDS patients are having some real problems," says Judith Auerbach, PhD, behavioral and social sciences coordinator at the Office of AIDS Research of the National Institute of Health in Bethesda, MD. "Think about what happens, for example, when you travel, and you’re crossing time zones. It’s very hard to do these regimens exactly right. Besides, we don’t even know yet what exactly right’ means."
Contrary to what common sense suggests, compliance rates for all populations and all diseases sort into the same predictable patterns, with factors such as demographics and severity of disease notwithstanding, says Janice W. Wohltmann, vice president and general manager of APREX, a division of Apria Healthcare, a Menlo Park, CA, firm that markets an electronic compliance-monitoring system.
"You can take almost any [disease] and overlay the compliance curves for them," says Wohltmann. "There’s always a group which will be exquisitely compliant, and a group that, even if you hit them over the head with a baseball bat, won’t comply. The rest are somewhere in the middle."
More specifically, between 50% and 70% of all patients are "good" at taking their pills, says John Urquhart, MD, chief scientist at APREX. About a sixth are utterly precise, leading Urquhart to dub them the "Swiss trains" of adherence; and about a sixth are totally unreliable.
Studies of adherence from other fields suggest that the sheer complexity of the new AIDS therapy regimens will probably detract from adherence. One such study found compliance suffers as the number of times per day patients must take pills increases; that is, patients on a once-daily regimen did better than those assigned to a twice-daily regimen. Patients on a thrice-daily dose schedule fared worse; and adherence fell again with a four-times-daily schedule.
But health care providers may not know about the drop in compliance, the same study found, because the subjects’ truthfulness in self-reports of pill-taking fell right along with their adherence.2
Noncompliance plagues other kinds of patients
The high stakes involved in compliance don’t seem to make a difference in behavior, says Wohltmann. She offers examples from two other arenas tuberculosis, and kidney transplants where patients’ lives depend on complying with regimens.
With TB patients, as practically everyone now knows, some patients’ persistent noncompliance has led them to develop strains of TB that are virtually incurable. It’s the same story with renal transplant patients, Wohltmann says.
"Remember, many of these people have spent years on dialysis, and years on a waiting list," she says. "Finally, they get their transplant. Many of them feel well for the first time in their lives. And for many, there won’t be a second chance at getting another kidney." Despite all this, the leading cause of death among renal transplant patients is failure to adhere to anti-rejection medications, Wohltmann adds.
For now, studies of adherence specifically related to the new therapies for AIDS still make up a relatively young field, whose practitioners are scrambling to come up with some useful information.
When Auerbach helped colleagues at the NIH organize a conference last fall on the subject of adherence to the new AIDS therapies, the lack of hard data surprised her, she says. "A lot of folks who’ve been working in research developing the drugs, or who are working in clinical practice, really know very little about adherence," she says. "What we’re seeing now is that these people are partnering up with social scientists, who’ve been looking at adherence all along."
Since no one knows how "forgiving" of lapses new therapies that include protease inhibitors will be, researchers aren’t even sure about the basics. For example, no one knows for sure how to define "adequate" adherence, says Auerbach.
"The really big question here is, how much adherence is enough? How much of a fudge factor are we talking about? We simply don’t know yet," she says.
One thing is certain, she says: Adherence doesn’t spring from individual behavior alone. "It’s a function of the relationship between the provi der, the patient, and the health care system," she adds. "People make a mistake by assuming adherence is just a function of the individual, and that you can batter someone into being adherent."
References
1. Eldred L, Wu A, Chaisson RE, et al. Adherence to antiretroviral therapy in HIV disease. Presented at the Fourth Conference on Retroviruses and Opportunistic Infections. Washington, DC; 1997.
2. Cramer JA, Mattson RH, Prevey ML, et al. How often is medication taken as prescribed? JAMA 1989; 261:3273-3277.
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