Adherence to Insulin in Singaporean Pediatric Type 1 Diabetes Patients and Its Impact on Glycemic Control and Health-Care Utilization

Abstract

Objective: Optimizing glycemic control is challenging with insulin non-adherence. This study aimed to characterize the prevalence of non-adherence among Singaporean pediatric patients with type 1 diabetes mellitus (T1DM) and investigate its associated outcomes.
 Methods: Singaporean patients with T1DM aged ≤18 years old with ≥1 year of insulin prescription between 2012 and 2016 were included in this retrospective, single-center longitudinal study. Patients on insulin pumps were excluded from the study. Non-adherence was defined as medication possession ratio (MPR) <100%. Glycemic control was defined using mean hemoglobin A1c (HbA1c) within the study period. Health-care utilization was defined as the number of outpatients, inpatient, and emergency visits. The t-test, Chi-square test, logistic regression, and Poisson regression were used to analyze means, proportions, factors associated with non-adherence, and association of non-adherence and health-care utilization, respectively. Sensitivity analyses were performed for MPR thresholds of 80% and 95%.
 Results: A total of 206 patients were included in this study. Non-adherent patients were older, had a longer duration of diabetes since diagnosis and shorter duration of follow-up. Gender, race, financial class, and number of concurrent medications were comparable between groups. The prevalence of non-adherence was 34.0% (95% confidence interval [CI]: 27.9–40.7%). Non-adherent patients had a higher average HbA1c (non-adherent: 9.6% [2.1] vs. adherent: 8.6% [1.3], p<0.001). Non-adherence was not associated with health-care utilization. Patients with >5 years of diabetes were more likely to be non-adherent.
 Conclusion: Non-adherence defined as MPR <100% is associated with poorer glycemic control. Further interventions may focus on patients with >5 years of diabetes to improve their adherence to insulin therapy.

Refill Adherence Measures and Its Association with Economic, Clinical, and Humanistic Outcomes Among Pediatric Patients: A Systematic Review

“…The MPR and PDC were the most common RAMs reported (n = 19) [25][26][27][29][30][31][32][33]36,37,[39][40][41][42][43][44][45][46]55]. The RAMs used in eight other studies were equivalent to the proportion of days with medication supply, similar to MPR and PDC [21,22,34,[50][51][52][53][54].…”

“…The studies were conducted in 10 different countries, the majority (n = 33) of which were high-income countries, according to The World Bank definition [56]. These include the United States of America (n = 23) [21][22][23][24][25][26][27]29,[31][32][33][34][35]39,41,[47][48][49][50][51][52][53][54], United Kingdom (n = 3) [30,38,46], Israel (n = 2) [43,45], Taiwan (n = 1) [42], Korea (n = 1) [37], Australia (n = 1) [55], Netherlands (n = 1) [36], and Singapore (n = 1) [44]. Only two studies were conducted in upper-middle-income countries such as Brazil (n = 1) [28], and Malaysia (n = 1) [40].…”

“…Asthma (n = 9) was the most common disease state involved in the studies [24,25,28,30,31,[34][35][36]51], followed by human immunodeficiency virus (HIV) infection (n = 6) [21][22][23]47,49,50]. The sources of medication refill data were pharmacy records (n = 19) in approximately half of the studies, [21][22][23]28,33,35,37,40,44,[46][47][48][49][50][51][52][53][54][55], and administrative claims database (n = 16) in the remaining studies [24][25][26][27][29][30][31][32]34,36,38,39,[41][42][43]…”

“…The remaining 29 studies defined adequate adherence with a fixed threshold below which patients were regarded as non-adherent. This ratio ranged from 0.08 in asthma [25], to 1.00 in HIV and type 1 diabetes (T1DM) [44,50]. Of the 27 studies with a fixed threshold to define adequate adherence, five studies derived its threshold from the study cohorts' percentiles or data distributions [25,27,33,36,41], while 10 studies utilized thresholds from prior studies [22,31,37,39,40,43,45,49,50,53].…”

“…Of the 27 studies with a fixed threshold to define adequate adherence, five studies derived its threshold from the study cohorts' percentiles or data distributions [25,27,33,36,41], while 10 studies utilized thresholds from prior studies [22,31,37,39,40,43,45,49,50,53]. The source of threshold used for the remaining 12 studies were not specified [21,24,34,35,38,42,44,[46][47][48]52,54]. Table S3 summarizes the reported relationship between medication adherence and ECHO.…”