Friday, September 01, 2006

Measuring Adherence

There are a variety of different ways that we can evaluate compliance -

Use the Doctors' Judgment. However doctors are notoriously poor at determining whether or not their patients have used medications.

Trust Patient's Self-Reports. Researchers are divided as to whether or not they believe self-reports. When patient reports have been compared to some objective measure of medicine taking, studies have tended to show that patients are accurate when they claim that they have not taken their medication. However, for those who claim that they have used the medication as prescribed, these verbal reports are often not confirmed by objective records (Spector et al., 1986).

Use of Objective Measures. For example, you can count pills, check pharmacy records, or weigh medicine containers that are used to distribute liquid medications. Using these methods requires that you understand exactly how much medicine the doctor had prescribed. There are also a variety of different problems that can lead to inaccurate assessments. For example, medications are often shared by other members of the household, given to friends, or simply dumped out. This is more true for particular types of medications such as tranquilizers and sleeping pills.

Use of Biochemical Analysis. Some medicines can be followed by examining blood, urine, or other bodily excretions. Sometimes a pharmacist can put a "marker substance" in the medication. Riboflavin, for example, can be added to medication as a method of tracking its use. There are other biochemical by-products that can be studied. For example, smokers can be detected by studying carbon monoxide in their blood or exhaled breath. Smoking can also be followed using tests for metabolites for nicotine. One of these is called cotinine. Although biochemical measures of compliance are attractive for the sake of accuracy, there are also some problems. For example, these measures often produce misleading findings. For instance, thyocynide, which is often used to evaluate cigarette smoking, can also be affected by other aspects of the Ps diet. Cabbage, for instance, increases thyocynide concentrations.

(Cited in Kaplan et al, 1993)

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