Chicken or Egg: poor adherence to DMDs is associated with treatment failure

Epub ahead of print
Ivanova et al. Impact of medication adherence to disease-modifying drugs on severe relapse, and direct and indirect costs among employees with multiple sclerosis in the US. J Med Econ. 2012 Mar 1.  

Objective: To compare rates of severe relapse and total direct and indirect costs over a 2-year period between US-based employees with MS who were adherent and non-adherent to disease-modifying drugs (DMDs). 

Methods: Employees with ≥1 MS diagnosis and ≥1 DMD pharmacy claim between 1/1/2002-12/31/2007 were identified from a large US administrative claims database. MS’ers had continuous coverage ≥6 months before (baseline) and ≥24 months after (study period) their index date (first DMD claim). Adherence was measured using medication possession ratio (MPR) over the study period. Patients with MPR ≥80% were considered adherent (n = 448) and those with MPR <80% as non-adherent (n = 200). 
“Medication Possession Ratio (MPR) = is the proportion of time you are taking your medication over the defined period; i.e. a ration of 50% means you are missing half of your injections.”
Analyses were used to compare rates of severe relapse (inpatient or Emergency Department visit with MS diagnosis) and costs in 2007 dollars between DMD adherent and non-adherent MS’ers. Direct costs were calculated as reimbursements to providers for medical services and prescription drugs excluding DMDs. Indirect costs included disability and medically-related absenteeism costs. 
Results: DMD adherent MS’ers were on average older (43.5 vs 41.8 years, p = 0.015) and more likely to be male (38.6% vs 26.0%, p = 0.002) compared with non-adherent MS’ers. 
“Interesting, I always thought woman were more likely to take their medication. Another misconception buried.”
Adherent MS’ers had lower rates of depression, higher rates of previous DMD use, and higher baseline MS-related costs. After adjusting for differences in baseline characteristics, DMD adherent MS’ers had a lower rate of severe relapse (12.4% vs 19.9%, p = 0.013) and lower total (direct and indirect) costs ($14,095 vs $16,638, p = 0.048) over the 2-year study period. 
Conclusions: In this study, DMD adherence was associated with a significantly lower rate of severe relapse and lower total costs over 2 years. Causality cannot be inferred because adherence and outcomes were measured over the same period. The study was subject to limitations associated with use of claims data and the absence of clinical measures.
“Chicken or Egg? Were the DMD responders more likely to be adherent than the non-responders? If you were having a lot of breakthrough relapse on an injectable DMD would you be more likely to miss injections or stop than if you were having no relapses?”

“Whatever the reason the message from this study is clear; you need to take your DMDs as prescribed to reap the maximal benefits. Non-adherence or in old speak, non-compliance, is a no-no. This is not a unique problem that is limited to the field of MS, but occurs in almost every speciality in medicine. Non-adherence is bad for the person with the disease and it costs money.”

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