Allergy, Asthma and Immunology: Accuracy of the days’ supply and the number of refills allowed recorded in Québec prescription claims databases for inhaled corticosteroids

BMJ Open

2014;4:e005903 doi:10.1136/bmjopen-2014-005903

Epidemiology

Lucie Blais1,2,3,

Anne Vilain1,

Fatima-Zohra Kettani1,2,

Amélie Forget1,2,

Geneviève Lalonde1,

Marie-France Beauchesne1,3,4,5,

Francine M Ducharme6,7,

Catherine Lemière1,2

+¹Faculté de Pharmacie, Université de Montréal, Montréal, Québec, Canada
²Hôpital du Sacré-Cœur de Montréal, Montréal, Québec, Canada
³Endowment Pharmaceutical Chair AstraZeneca in Respiratory Health, Montréal, Québec, Canada
⁴Pharmacy Department, Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, Québec, Canada
⁵Centre de Recherche Clinique Étienne-Le Bel, Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, Québec, Canada
⁶Clinical Research and Knowledge Transfer Unit on Childhood Asthma, Research Centre, CHU Sainte-Justine, Montréal, Canada
⁷Department of Pediatrics, University of Montréal, Montréal, Québec, Canada.
Correspondence to Dr Lucie Blais; lucie.blais@umontreal.ca

Objectives and hypotheses Adherence to inhaled corticosteroids (ICS) is a major issue in asthma. This study aimed to estimate the accuracy of the days’ supply and number of refills allowed, variables recorded in Québec claims databases and used to estimate adherence, and to develop correction factors, if required. We hypothesised that the accuracy of the days’ supply for ICS would be low whereas the accuracy of the number of refills allowed would be high.

Setting 40 community pharmacies in Québec (Canada) and a medication registry.

Participants We collected data for 1108 ICS original prescriptions stored in the 40 pharmacies (sample 1), and we obtained a second sample of 2676 ICS prescriptions selected from reMed, a medication registry (sample 2).

Primary and secondary outcomes We estimated the concordance of the days’ supply and number of refills between Québec claims databases and the original prescription from sample 1. We developed a correction factor for the days’ supply in sample 1 and validated it in sample 2. Analyses were stratified by age: 0–11 and 12–64 years.

Results In sample 1, the concordance for the days’ supply was 39.6% (95% CI 37.6% to 41.6%) in those aged 0–11 years and 56% (54.9% to 57.2%) in those aged 12–64 years. The concordance increased to 59.4% (58.2% to 60.5%) in those aged 0–11 years and 74.2% (73.5% to 74.9%) in those aged 12–64 years after applying the correction factors in sample 2. The concordance for the refills allowed was 92.1% (91% to 93.1%) in those aged 0–11 years and 93.1% (92.5% to 93.7%) in those aged 12–64 years in sample 1.

Conclusions The accuracy of the days’ supply was moderate among those aged 0–11 years and substantial among those aged 12–64 years after applying the correction factors. The accuracy of the number of refills was almost perfect in both groups.

This validation study used a representative large population-based sample of inhaled corticosteroid (ICS) prescriptions covering patients up to 65 years of age.
Correction factors for the days’ supply of ICS, used in the assessment of medication adherence, were developed and validated in an independent second large sample.
This study is the first one to evaluate the accuracy of the number of refills allowed, also used in adherence calculation.
Patients aged >65 years were not considered since the prescription drug database used for this study does not include them.
The clinical indication for the ICS prescriptions was unknown.