Implementation of a Health Plan Program for Switching From Analogue to Human Insulin and Glycemic Control Among Medicare Beneficiaries With Type 2 Diabetes

Abstract

Importance: Prices for newer analogue insulin products have increased. Lower-cost human insulin may be effective for many patients with type 2 diabetes.

Objective: To evaluate the association between implementation of a health plan-based intervention of switching patients from analogue to human insulin and glycemic control.

Design, setting, and participants: A retrospective cohort study using population-level interrupted times series analysis of members participating in a Medicare Advantage and prescription drug plan operating in 4 US states. Participants were prescribed insulin between January 1, 2014, and December 31, 2016 (median follow-up, 729 days). The intervention began in February 2015 and was expanded to the entire health plan system by June 2015.

Exposures: Implementation of a health plan program to switch patients from analogue to human insulin.

Main outcomes and measures: The primary outcome was the change in mean hemoglobin A1c (HbA1c) levels estimated over three 12-month periods: preintervention (baseline) in 2014, intervention in 2015, and postintervention in 2016. Secondary outcomes included rates of serious hypoglycemia or hyperglycemia using ICD-9-CM and ICD-10-CM diagnostic codes.

Results: Over 3 years, 14 635 members (mean [SD] age: 72.5 [9.8] years; 51% women; 93% with type 2 diabetes) filled 221 866 insulin prescriptions. The mean HbA1c was 8.46% (95% CI, 8.40%-8.52%) at baseline and decreased at a rate of -0.02% (95% CI, -0.03% to -0.01%; P <.001) per month before the intervention. There was an association between the start of the intervention and an overall HbA1c level increase of 0.14% (95% CI, 0.05%-0.23%; P = .003) and slope change of 0.02% (95% CI, 0.01%-0.03%; P < .001). After the completion of the intervention, there were no significant differences in changes in the level (0.08% [95% CI, -0.01% to 0.17%]) or slope (<0.001% [95% CI, -0.008% to 0.010%]) of mean HbA1c compared with the intervention period (P = .09 and P = 0.81, respectively). For serious hypoglycemic events, there was no significant association between the start of the intervention and a level (2.66/1000 person-years [95% CI, -3.82 to 9.13]; P = .41) or slope change (-0.66/1000 person-years [95% CI, -1.59 to 0.27]; P = .16). The level (1.64/1000 person-years [95% CI, -4.83 to 8.11]; P = .61) and slope (-0.23/1000 person-years [95% CI, -1.17 to 0.70]; P = .61) changes in the postintervention period were not significantly different compared with the intervention period. The baseline rate of serious hyperglycemia was 22.33 per 1000 person-years (95% CI, 12.70-31.97). For the rate of serious hyperglycemic events, there was no significant association between the start of the intervention and a level (4.23/1000 person-years [95% CI, -8.62 to 17.08]; P = .51) or slope (-0.51/1000 person-years [95% CI, -2.37 to 1.34]; P = .58) change.

Conclusions and relevance: Among Medicare beneficiaries with type 2 diabetes, implementation of a health plan program that involved switching patients from analogue to human insulin was associated with a small increase in population-level HbA1c.

Figure 1.. Participant Flow Diagram for a Study Examining the Effects of an Intervention Aimed at Switching Medicare Beneficiaries With Type 2 Diabetes From Analogue to Human Insulin

Figure 2.. Mean Hemoglobin A_1c (HbA_1c) of Insulin Users Before, During, and After an Insulin Conversion Intervention

The shaded area represents the intervention period of January 1, 2015, through December 31, 2015. The shading around the data points indicate 95% CIs. Changes in the mean level (circles) and slope (solid lines) of HbA_1c were estimated using interrupted time series models (segmented regression analysis) with cut points at the start of 2015 and 2016. Because HbA_1c may lag up to 3 months, study participants only contributed HbA_1c data if they had an insulin dispensed either in the same month of the laboratory result or within 3 months before.

Figure 3.. Rate of Serious Hypoglycemic and Hyperglycemic Events Among Insulin Users Before, During, and After an Insulin Conversion Intervention.

The shaded area represents the intervention period of January 1, 2015, through December 31, 2015. Changes in the mean level (circles) and slope (solid lines) of serious hypoglycemic events (A) and hyperglycemic events (B) were estimated using interrupted time series models (segmented regression analysis) with cut points at the start of 2015 and 2016. Study participants contributed hypoglycemic or hyperglycemic events only if they had been dispensed insulin during the same month as their clinical event. Participants could contribute more than 1 event.

Figure 4.. Proportion of Analogue vs Human Insulin Products Dispensed by Calendar Month and Year Among Insulin Users and Total Monthly Expenditures for Insulin Products Dispensed in a Medicare Advantage Plan

The insulin switching intervention was implemented throughout the health system by 2015.

Figure 5:. Kaplan-Meier Survival Curves for Reaching the Medicare Part D Coverage Gap Comparing Insulin Users in 2014, 2015, and 2016

Reaching the coverage gap indicates that a Medicare beneficiary has surpassed the annual initial coverage threshold, and, from that point on, is responsible for substantially larger out-of-pocket expenses for outpatient prescriptions covered by their Medicare Part D plan. The hazard ratio comparing 2016 and 2014 is 0.45 (95% CI, 0.43-0.48; P < .001 using a robust sandwich estimator). Median (interquartile range) length of follow-up was 7 (5-10) months in 2014, 6 (4-10) months in 2015, and 11 (7-12) months in 2016.