REVIEW – March 2006

Adherence: estimation and determinants


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Adherence may be defined as the extent to which the patient’s behaviour coincides with medical advice. Adherence is usually calculated as the number of pills taken divided by the number of pills that should be taken during the treatment period. Often 80% of the dose is considered sufficient to be regarded as adherent. Although proportions give an opportunity to compare patients’ behaviours, the actual difference between high  and low adherence depends on the drug dose-response relationship. Adherence is a complex phenomenon determined by socioeconomic, health team, health care, condition, therapy and patient related factors. A set of measurements is used to assess adherence. Current methods for improving adherence are counselling, reminders, family therapy and other forms of additional supervision or attention.