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Around one third to one half of patients do not take their medicines as directed, yet this is not usually considered to be a medical error. Should this be the case? This article explores whether it should, and argues that there are benefits in applying the literature on errors to non-compliance.
Non-compliance is a substantial and, as yet, intractable issue; any new insights into it are to be welcomed. Estimates have remained constant over the years, that 30-50% of patients on chronic medication do not take their medicines as directed. 1, 2 We do not know the full consequences of non-compliance on the population as a whole. The economic studies have been limited, but all of them suggest substantial consequences. In 1985 Smith estimated cardiovascular non-compliance alone resulted in 125 000 deaths in the USA annually and a further $1.5bn in lost earnings from hospitalisations. 3 Another study suggested non-compliance to just 10 drugs cost the USA between $396 and $792 million each year, 4 and the overall cost to the USA of all non-compliance is estimated at $100bn annually. 5
The mutual exclusion of non-compliance and errors is fairly comprehensive. I failed to find any mention of non-compliance in a quick skim of my books on error, so I searched Medline over the last quarter century. Using the terms "patient compliance OR medication errors" there were 24 702 references; searching for "patient compliance AND medication errors" and restricting the search to "English" and "journal article" reduced the number to just 50. Most of these were studies in which the authors simply regarded non-compliance as an error but did not address it with reference to any literature on errors. An exception was the American Society of Hospital Pharmacists which did include non-compliance in its guidelines on preventing medication errors in hospitals. 6 Considering the development of the literature on the causes of errors, the growing application of human error theory in medicine, and national initiatives to reduce errors in the UK and USA, it seems a good time to reassess whether the overlap should be so small.
NON-COMPLIANCE
To understand the reasons for the separation of these two literatures, we need first to understand the definitions and causes of non-compliance. Compliance is usually defined...