Dear JAMA,
In reply In our article1, we reported significant CGM-related changes in telephone and outpatient visits for our entire study cohort. However, as Chu noted, there was a subgroup difference. While the change in outpatient visits was significant for patients with type 1 diabetes, it was not significant for patients with type 2 diabetes. Note that far fewer patients with type 2 diabetes initiated CGM (n=344), as compared to type 1 diabetes initiators (n=3,462). This set a higher bar for reaching statistical significance in the type 2 diabetes population, making the statistically significant improvement in HbA1c and reduction in hypoglycemia in this small subgroup notable.
Chu also noted some covariates (e.g., being Hispanic or neighborhood deprivation) remained imbalanced (standardized difference|≥0.1|) despite overlap weighting. The weighting approach effectively balanced most but not all covariates. We addressed remaining covariate imbalances by statistical adjustment in the difference-in-differences models.
We also reported underuse of real-time CGM in some minorities, those with limited English proficiency and those living in deprived neighborhoods. Chu implicates “strict requirements for medical insurance coverage of CGM” as the probable explanation for such underuse. We find that unlikely given our study population was fully insured and CGM eligibility requirements are clinically based and applied uniformly to all patients, regardless of race/ethnicity, language or social status.
Underuse of CGM in vulnerable populations has been noted in other populations and healthcare settings;2–5 it remains unclear whether this pattern is due to patient (e.g., lack of engagement), provider (e.g., unconscious bias) or system level (e.g., benefit generosity) factors. We agree that understanding the root causes of social inequities in CGM use requires further investigation and healthcare systems need to develop approaches to eliminating these disparities. While beyond the scope of our paper, we also agree that a better understanding of the cost-effectiveness of CGM on type 2 diabetes is warranted.
Contributor Information
Andrew J Karter, Kaiser Permanente Division of Research, Oakland, California.
Lisa K. Gilliam, Endocrinology and Internal Medicine, Kaiser Permanente, South San Francisco Medical Center, South San Francisco, CA 94080.
Richard Dlott, Endocrinology and Clinical Informatics, Kaiser Permanente, Diablo Service Area, Martinez, CA 94553.
References
- 1.Karter AJ, Parker MM, Moffet HH, Gilliam LK, Dlott R. Association of Real-time Continuous Glucose Monitoring With Glycemic Control and Acute Metabolic Events Among Patients With Insulin-Treated Diabetes. JAMA. 2021;325(22):2273–2284. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Addala A, Auzanneau M, Miller K, et al. A Decade of Disparities in Diabetes Technology Use and HbA1c in Pediatric Type 1 Diabetes: A Transatlantic Comparison. Diabetes Care. 2021;44(1):133–140. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3.Walker AF, Hood KK, Gurka MJ, et al. Barriers to Technology Use and Endocrinology Care for Underserved Communities With Type 1 Diabetes. Diabetes Care. 2021. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 4.Lai CW, Lipman TH, Willi SM, Hawkes CP. Racial and Ethnic Disparities in Rates of Continuous Glucose Monitor Initiation and Continued Use in Children With Type 1 Diabetes. Diabetes Care. 2021;44(1):255–257. [DOI] [PubMed] [Google Scholar]
- 5.Foster NC, Beck RW, Miller KM, et al. State of Type 1 Diabetes Management and Outcomes from the T1D Exchange in 2016–2018. Diabetes Technol Ther. 2019;21(2):66–72. [DOI] [PMC free article] [PubMed] [Google Scholar]