Impact on glycated haemoglobin of a biological response‐based measure of medication adherence. Issue 9 (20th May 2015)

• Record Type: Journal Article
• Authors: Nichols, G. A.; Rosales, A. G.; Kimes, T. M.; Tunceli, K.; Kurtyka, K.; Mavros, P.; Steiner, J. F.
• Is Part Of: Diabetes, obesity & metabolism. Volume 17:Issue 9(2015:Sep.)
• Page Start: 843
• Page End: 848
• Publication Date: 2015-05-20
• Subjects: Diabetes -- Periodicals; Obesity -- Periodicals; Metabolism -- Disorders -- Periodicals; Clinical pharmacology -- Periodicals; 616.462
• DOI: 10.1111/dom.12476
• Languages: English
• ISSNs: 1462-8902

Abstract

<abstract abstract-type="main" id="dom12476-abs-0001"> <title> <x xml:space="preserve">Abstract</x> </title> <sec id="dom12476-sec-0009" sec-type="section"> <title>Aims</title> <p>The aim of this study was to examine the relationship between a specific glycated haemoglobin (HbA1c) measurement and a pharmaceutical dispensings‐based measure of adherence calculated over the 90 days before each HbA1c measure among patients who have newly initiated metformin therapy.</p> </sec> <sec id="dom12476-sec-0010" sec-type="section"> <title>Methods</title> <p>We identified 3109 people with type 2 diabetes who initiated metformin as their first‐ever antihyperglycaemic drug, analysing all 9918 HbA1c measurements that were taken over the next 2 years. We used an adaptation of the 'proportion of days covered' method for assessing medication adherence that corresponded to an ∼90‐day interval preceding an HbA1c measurement, terming the adaptation the 'biological response‐based proportion of days covered' (BRB‐PDC). To account for multiple observations per patient, we analysed the association between HbA1c and BRB‐PDC within the generalized estimating equation framework. Analyses were stratified by HbA1c level before metformin initiation using a threshold of 8% (64 mmol/mol).</p> </sec> <sec id="dom12476-sec-0011" sec-type="section"> <title>Results</title> <p>After multivariable adjustment using 0% adherence as the reference category, BRB‐PDC in the range 50–79% was associated with HbA1c values lower by −0.113 [95% confidence interval (CI) −0.202, −0.025] among patients with pre‐metformin HbA1c <italic><</italic>8%, and by −0.247 (95% CI −0.390, −0.104) among those with HbA1c ≥8% at metformin initiation. Full adherence (≥80%) was associated with HbA1c values lower by −0.175% (95% CI −0.257, −0.093) and by −0.453% (95% CI −0.586, −0.320).</p> </sec> <sec id="dom12476-sec-0012" sec-type="section"> <title>Conclusions</title> <p>Using this novel short‐interval approach that more closely associates adherence with the expected biological response, the association between better adherence and HbA1c levels was considerably stronger than has been previously reported; however, the strength of the impact was dependent upon the HbA1c level before initiating metformin.</p> </sec> </abstract>