Can one or two simple questions predict poor medication adherence?

Poor adherence to evidence-based medications is a major problem in conventional clinical practise. Better prognostic tools are needed to identify those with the highest likelihood of being non-adherent. The objective of this study is to determine if a 2-item patient activation status (PAS) measure identifies Medicare beneficiaries at risk of poor adherence to drugs typically recommended in treating type 2 diabetes.

PAS and medication adherence were assessed for respondents to the 2009 Medicare Current Beneficiary Survey and then compared using bivariate and multivariate tests. Participants' PAS was classified as "active," "high effort," "complacent," or "passive" based on how confident they were in identifying needed medical care and whether they brought medication lists to their doctors' visits. Adherence with oral antidiabetic drugs, angiotensin-converting enzyme-inhibitors/angiotensin receptor blockers, and statins was assessed using proportion of days covered (PDC).

A total of 940 Medicare beneficiaries with diabetes enrolled in Part D plans in 2009. The overall effect of PAS on medication adherence was small (3% lower PDC for complacent/passive vs active/high effort beneficiaries, P < 0.10). However, interactions of complacent/passive PAS with other characteristics associated with poor adherence identified certain subgroups as especially prone to problematic adherence: age < 65 (PDC -11%, P < 0.05), non-Hispanic black (PDC -13%, P < 0.05), and morbidly obese (-9%, P < 0.10).

A single question relating to taking medication lists to doctor visits may help identify patient subgroups prone to poor adherence in conventional practise, but larger samples are necessary to validate and extend these findings.