Adherence: The Furnace Filter Analogy

FEBRUARY 01, 2007
Jeannette Yeznach Wick, RPh, MBA, FASCP

If you ask furnace repairmen to describe the greatest frustration of the trade, you will hear a familiar story. Even though the repairmen remind people and offer ways for them to remember, most people fail to clean or replace their furnace filters monthly. If people do remember, they may not do the job correctly or well. That problem sounds similar to a problem that health care providers face every day: medication and treatment adherence. Consider these facts:

More than 29% of adults have hypertension (HTN)1,2 and are at increased risk for adverse outcomes. Although effective treatment reduces risk,3,4 most patients with HTN have poorly controlled blood pressure,5,6 and up to 70% of patients are nonadherent with prescription medication.1,7-9

Among diabetics treated with sulfonylureas, adherence is estimated to be as low as 10% to 50%.10

Among HIV-infected people, high-level adherence (in the range of 90% to 95% of doses taken correctly) is necessary to prevent viral resistance and to improve immunologic, virologic, and clinical outcomes. Regardless, adherence often is reported to be less than 70%.11

Most pharmacists know some of the factors that increase the risk of nonadherence:

  • Increasing numbers of drugs and doses
  • Difficult administration routes or timing
  • Silent or symptomless diseases
  • Cost of medications
  • Intolerable side effects

In the past, health care clinicians have used patient self-report, clinician impression, pill counts, pharmacologic tracers, and electronic measurement devices to assess adherence. Examination of pharmacy claims data is a recent method that allows access to aggregate data on medication dosing and refill patterns. The new buzzword is medication possession ratio (MPR),12,13 which now is used frequently as an adherence measure.10,12-25 (see sidebar).

Poor medication adherence is different from poor furnace filter maintenance in that furnace repairmen do not have aggregated statistics about nonadherence as pharmacists do. Ultimately, statistics do not create change in and of themselves, and direct-care clinicians have to intervene. Medication adherence and furnace filter maintenance are similar in that access and cost can be barriers, and cultural beliefs or misinformation also may be important.

Hypertensive patients, for example, often indicate that they become nonadherent because they believe that they are cured (46%), or they perceive that their prescribing clinician directed them to stop (25%).26 Patients may forget to take medications, misunderstand when or how to take them, take extra doses to treat stubborn symptoms, or consciously decide to stop taking medications.27 Clinicians may be ignorant of these problems and may interpret unidentified nonadherence as poor drug effectiveness.

Communication technique is key to improving adherence, especially communication that employs a patient-centered approach that allows patients to participate in shared decision making.28-31 Unfortunately, physicians rarely engage patients in decision making: often they just inform patients of the need for medication.30 They also are unlikely to question patients about medication-taking behaviors.32

Changing Behavior

Clinicians cannot expect to change patient behaviors without first knowing current medication-taking behaviors. Asking questions is the cornerstone of the approach, and most communication experts recommend using direct and information-intensive approaches to assessing adherence.33 Despite decades of education directed at health care providers to improve communication, providers frequently use inappropriate structure, temporality, content, and style when asking patients about adherence.34

The structure of a question either promotes or inhibits the amount and kind of information sharing from patients. Patients will respond to closed-ended questions with a simple yes or no, rarely venturing any additional information. Declarative questions (eg, "You take your medication, right?") also squelch patients' propensity to volunteer extensive information. Patients are not being intentionally dishonest; instead they engage in the human tendency to be agreeable. (My last furnace repairperson used to say, "You change your filter monthly, right?" Of course, I agreed.)

Switching to a subtly interrogative, open-ended question approach that uses question strings allows collaboration and also permits patients to verbalize concerns and beliefs. Pharmacists can say, "Tell me how you take this prescription," and then help the patient see how to improve. The result should improve adherence.34

Providers also need to simplify their communication. Asking about medications by pharmaceutical or trade names can confuse some patients. Describing tablet or capsule color and size can prompt better responses, especially for patients with low health literacy.35,36 Confrontational communication styles will tend to make patients defensive and will erode potential provider-patient therapeutic alliances (eg, "Didn't I tell you to take it in the morning on an empty stomach?").37,38 Providers who insist on communication that transfers information to the patient rather than exchanges information collaboratively miss an opportunity to improve adherence.39-41

In addition to communication barriers, patients' beliefs about medication also may contribute to problems with communicating about medication taking.42 Demographics such as age, gender, race, intelligence, level of education, marital status, and social status generally do not contribute to or affect adherence. Elders' adherence problems usually are related more closely to the medication regimen's characteristics than to age itself. Limited access to health care, financial problems, and lack of social support can undermine adherence.43

End Note

My furnace repairperson cajoled me into being more adherent to my furnace maintenance schedule. He pointed out barriers (poor location, dirty job); factors that increased my risk of poor outcome (multiple animals in the house); and the inevitable outcome if I failed to adhere (costly furnace repairs). He taught me ways to remember (put a note in with my bills payable, ask for help from family members). Then, he stuck out his hand to shake and said, "Promise you'll do better." We established an informal "contract," and my adherence is better.

Try a similar approach when you counsel patients about improving adherence, but realize that the patients with whom you can expect to see the best return on investment are those that are mildly to moderately nonadherent. Do not expect to change patients who are completely nonadherent into adherence stars. Nevertheless, do not let a counseling opportunity pass you by. It may very well be the one that may promote some positive change.

Ms. Wick is a senior clinical research pharmacist at the National Cancer Institute, National Institutes of Health, Bethesda, Md. The views expressed are those of the author and not those of any government agency.


1. Hajjar I, Kotchen TA. Trends in prevalence, awareness, treatment, and control of hypertension in the United States, 1988-2000. JAMA. 2003;290:199-206.

2. Chobanian A, Bakris GL, Black HR, et al. Seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. Hypertension. 2003;42:1206-1252.

3. Amery A, Birkenhager W, Brixko P, et al. Mortality and morbidity results from the European Working Party on High Blood Pressure in the Elderly trial. Lancet. 1985;1:1349-1354.

4. Prevention of stroke by antihypertensive drug treatment in older persons with isolated systolic hypertension: final results of the Systolic Hypertension in the Elderly Program (SHEP). JAMA. 1991;265:3255-3264.

5. Jamerson K, DeQuattro V. The impact of ethnicity on response to antihypertensive therapy. Am J Med. 1996;101:22S-32S.

6. Winickoff R, Murphy PK. The persistent problem of poor blood pressure control. Arch Intern Med. 1987;147:1393-1396.

7. Management of patient compliance in the treatment of hypertension: report of the NHLBI Working Group. Hypertension. 1982;4:415-423.

8. Sackett DL, Snow JC. The magnitude of compliance and noncompliance. In: Haynes RB, Taylor DW, Sackett DL, eds. Compliance in Health Care. Baltimore, MD: Johns Hopkins University Press; 1979:11-22.

9. Clark LT. Improving compliance and increasing control of hypertension: needs of special hypertensive populations. Am Heart J. 1991;121(suppl):664.

10. Sclar DA, Robison LM, Skaer TL, Dickson WM, Kozma CM, Reeder CE. Sulfonylurea pharmacotherapy regimen adherence in a Medicaid population: influence of age, gender, and race. Diabetes Educ. 1999;25:531-538.

11. Mugavero M, Ostermann J, Whetten K, et al. Barriers to antiretroviral adherence: the importance of depression, abuse, and other traumatic events. AIDS Patient Care STDS. 2006;20:418-428.

12. Sclar DA, Chin A, Skaer TL, Okamoto MP, Nakahiro RK, Gill MA. Effect of health education in promoting prescription refill compliance among patients with hypertension. Clin Ther. 1991;13:489-495.

13. Sclar DA, Skaer TL, Chin A, Okamoto MP, Gill MA. Utility of a transdermal delivery system for antihypertensive therapy: Pt 2. Am J Med. 1991;91:57S-60S.

14. Skaer TL, Sclar DA, Markowski DJ, Won JK. Effect of value-added utilities on prescription refill compliance and Medicaid health care expenditures?a study of patients with non-insulin-dependent diabetes mellitus. J Clin Pharm Ther. 1993;18:295-299.

15. Skaer TL, Sclar DA, Markowski DJ, Won JK. Effect of value-added utilities on prescription refill compliance and health care expenditures for hypertension. J Hum Hypertens. 1993;7:515-518.

16. Skaer TL, Sclar DA, Markowski DJ, Won JK. Utility of a sustained-release formulation for antihypertensive therapy. J Hum Hypertens. 1993;7:519-522.

17. Sclar DA, Robison LM, Skaer TL, et al. Antidepressant pharmacotherapy: economic evaluation of fluoxetine, paroxetine, and sertraline in a health maintenance organization. J Int Med Res. 1995;23:395-412.

18. Okano GJ, Rascati KL, Wilson JP, Remund DD, Grabenstein JD, Brixner DI. Patterns of antihypertensive use among patients in the US Department of Defense database initially prescribed an angiotensin-converting enzyme inhibitor or calcium channel blocker. Clin Ther. 1997;19:1433-1445.

19. Steiner JF, Prochazka AV. The assessment of refill compliance using pharmacy records: methods, validity, and applications. J Clin Epidemiol. 1997;50:105-116.

20. Hurley JS, Frost EJ, Trinkaus KM, Buatti MC, Emmett KE. Relationship of compliance with hormone replacement therapy to short-term healthcare utilization in a managed care population. Am J Manag Care. 1998;4:1691-1698.

21. Blanford L, Dans PE, Ober JD, Wheelock C. Analyzing variations in medication compliance related to individual drug, drug class, and prescribing physician. J Manag Care Pharm. 1999;5:47-51.

22. Roe CM, Motheral BR, Teitelbaum F, Rich MW. Angiotensin-converting enzyme inhibitor compliance and dosing among patients with heart failure. Am Heart J. 1999;138:818-825.

23. Lawrence M, Guay DRP, Benson SR, Anderson MJ. Immediate-release oxybutynin versus tolterodine in detrusor overactivity: a population analysis. Pharmacotherapy. 2000;20:470-475.

24. Xuan J, Duong PT, Russo PA, Lacey MJ, Wong B. The economic burden of congestive heart failure in a managed care population. Am J Manag Care. 2000;6:693-700.

25. Sikka R, Xia F, Aubert RE. Estimating medication persistency using administrative claims data. Am J Manag Care. 2005;11:449-457.

26. Gallup G Jr, Cotugno HE. Preferences and practices of Americans and their physicians in antihypertensive therapy. Am J Med. 1986;81:20-24.

27. Horne R, Clatworthy J, Polmear A, Weinman J. Do hypertensive patients' beliefs about their illness and treatment influence medication adherence and quality of life? J Hum Hypertension. 2001;15(suppl 1):S65-S68.

28. Theunissen NC, de Ridder DT, Bensing JM, Rutten GE. Manipulation of patient-provider interaction: discussing illness representations or action plans concerning adherence. Patient Educ Couns. 2003;51:247-258.

29. Ogedegbe G, Harrison M, Robbins L, Mancuso CA, Allegrant JP. Barriers and facilitators of medication adherence in hypertensive African Americans: a qualitative study. Ethn Dis. 2004;14:3-12.

30. Stevenson FA, Barry C, Britten N, Barber N, Bradley CP. Doctor-patient communication about drugs: the evidence for shared decision making. Soc Sci Med. 2000;50:829-840.

31. Ockene JK, Kristeller J, Goldberg R, et al. Increasing the efficacy of physician-delivered smoking interventions: a randomized clinical trial. J Gen Intern Med. 1991;6:1-8.

32. Kjellgren KI, Svensson S, Ahlner J, Saljo R. Antihypertensive medication in clinical encounters. Int J Cardiol. 1998;64:161-169.

33. Steele DJ, Jackson TC, Gutmann MC. Have you been taking your pills? The adherence-monitoring sequence in the medical interview. J Fam Pract. 1990;30:294-299.

34. Bokhour BG, Berlowitz DR, Long JA, Kressin NR. How do providers assess antihypertensive medication adherence in medical encounters? J Gen Intern Med. 2006;21:577-583.

35. Baker DW, Parker RM, Williams MV, et al. The health care experience of patients with low literacy. Arch Fam Med. 1996;5:329-334.

36. Kalichman SC, Ramachandran B, Catz S. Adherence to combination antiretroviral therapies in HIV patients of low health literacy. J Gen Intern Med. 1999;14:267-273.

37. Mead M, Bower P. Patient-centredness: a conceptual framework and review of the empirical literature. Soc Sci Med. 2000;51:1087-1110.

38. Kjellgren KI, Ahlner J, Saljo R. Taking antihypertensive medication?controlling or co-operating with patients? Int J Cardiol. 1995;47:257-268.

39. Braddock CH 3rd, Edwards KA, Hasenberg NM, Laidley TL, Levinson W. Informed decision making in outpatient practice: time to get back to basics. JAMA. 1999;282:2313-2320.

40. Frankel RM, Terry S. Getting the most out of the clinical encounter: the four habits model. Permanente J. 1999;3(3):1-8.

41. Lee R, Garvin T. Moving from information transfer to information exchange in health and health care. Soc Sci Med. 2003;56:449-464.

42. Ong LM, de Haes JC, Hoos AM, Lammes FB. Doctor-patient communication: a review of the literature. Soc Sci Med. 1995;40:903-918.

43. American Pharmacists Association. Medication Compliance-Adherence-Persistence (CAP) Digest. Washington, DC: APhA and Pfizer Pharmaceuticals; 2003.


CDC: Improved HIV Care Needed for African Americans

Although the annual HIV diagnosis rate between 2010 and 2014 decreased for black individuals by 16.2%, blacks remain disproportionately affected by HIV/AIDS.


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