REVIEW ARTICLE

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UNDERSTANDING PATIENT MANAGEMENT: THE NEED FOR MEDICATION ADHERENCE AND PERSISTENCE

MEASUREMENT OF MEDICATION ADHERENCE

There are various ways to measure medication adherence.¹⁴ They can vary from self-reporting to electronic monitoring. Broadly the methods can be classified into 3 categories.

1. subjective egg patient interview
2. direct ( e.g. analysis of drug levels)
3. indirect ( e.g. pill counting, prescription refills, electronic monitoring of medication use)

Each of these methods has their own advantages and disadvantages

Subjective measurement

An example of this subjective evaluation is by using the Morisky Mediation Taking Behaviour Scale.¹⁵ It consists of 4 items and is simple and practical to use. Questions include “Do you ever forget to take your medicine?”; “Are you careless at times about taking your medicine?”  When used for example in hypertension management, the blood pressure is less likely to be controlled if answers are in the affirmative “yes”

Self-reporting is often inaccurate because of difficulties of recall, attempts to please the health care provider or a combination of these reasons. Furthermore doctors tend to overestimate medication adherence in their patients as patients tend to want to please their doctors and answers what the doctors want to hear.¹⁶ Studies have shown poor correlation between the doctor’s estimate and objective pill counts. Doctors’ judgement has low sensitivity (<40%) but good specificity (90%),^17,18 in other words good at detecting good adherence but not good at detecting poor or partial adherence.  

Direct measurement

Measuring drugs levels in blood or urine can be a good method of determining poor or good adherence. It is of particular use in patients on anti-epileptic medications like phenytoin or Valproic acid. However such tests are expensive and burdensome to health care providers. Furthermore it s open to manipulation by patients where patients dutifully take the medication when the tests are about to be done giving a false impression of good adherence.  

Directly observing the patient take the medication is probably the most accurate method. This has been used successfully for short-term treatment like tuberculosis (DOTS) but is expensive and impractical for routine use in particular for conditions like diabetes mellitus and hypertension where long term drug treatment is needed.

Indirect methods

Most of the indirect methods like diaries, pill count, prescription refills (medication collected but not ingested) and even electronic monitoring (pills taken out but again not ingested)^{19, 20} are subject to patient distortion. The advantages of these methods are that they are inexpensive and are practical and generally easy to perform.

IDENTIFYING POOR ADHERENCE

Race, sex and socio-economic status do not seem be consistently associated with poor adherence.²¹ However there are some predictors of poor adherence Box 1. The presence of these predictors should alert us to the possibility of poor adherence.

The simplest, albeit inaccurate, way of detecting poor adherence in a busy clinical setting is to ask the patient non-judgementally. Phrased as “I know it must be difficult to take all your medications regularly. How often do you miss them?” makes the patient feel more comfortable in telling the truth and helps identify poor adherence. Patients who admit to miss taking medication are probably candid.

Medication adherence is dynamic and is not constant over time. Most deviations are omissions and delays in timing of doses. Partial adherence occurs where medication taking improves about 5 days before and 5 days after a scheduled clinic visit but thereafter declines. This phenomena has been refereed to as “white coat–adherence”^22,23 Recognition of the dynamic nature of adherence is important when considering ways to improve poor medication taking. 

Asking for adverse effects of medication is important as presence of side-effects is likely to make the patient not take the medication. Furthermore, asking whether they know why taking the medication and the benefits of taking their medication may expose poor adherence.

Box 1. Predictors of poor adherence

Adapted with permission Ref 14.