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The American Journal of Managed Care November 2014
The Correlation of Family Physician Work With Submitted Codes and Fees
Richard Young, MD, and Tiffany L. Overton, MPH
Population Targeting and Durability of Multimorbidity Collaborative Care Management
Elizabeth H.B. Lin, MD, MPH; Michael Von Korff, ScD; Do Peterson, MS; Evette J. Ludman, PhD; Paul Ciechanowski, MD, MPH; and Wayne Katon, MD
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Alfred B. Engelberg, JD
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Variation in Hospital Inpatient Prices Across Small Geographic Areas
Jared Lane K. Maeda, PhD, MPH; Rachel Mosher Henke, PhD; William D. Marder, PhD; Zeynal Karaca, PhD; Bernard S. Friedman, PhD; and Herbert S. Wong, PhD
Medical Cost Burdens Among Nonelderly Adults With Asthma
Emily Carrier, MD, and Peter Cunningham, PhD
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William H. Shrank, MD, MSHS; Andrew Sussman, MD; and Troyen A. Brennan, MD, JD
Care Coordination Measures of a Family Medicine Residency as a Model for Hospital Readmission Reduction
Wayne A. Mathews, MS, PA-C
Medication Adherence and Readmission After Myocardial Infarction in the Medicare Population
Yuting Zhang, PhD; Cameron M. Kaplan, PhD; Seo Hyon Baik, PhD; Chung-Chou H. Chang, PhD; and Judith R. Lave, PhD
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Switching from Multiple Daily Injections to CSII Pump Therapy: Insulin Expenditures in Type 2 Diabetes
Guy David, PhD; Max Gill, MBA, Candace Gunnarsson, EdD; Jeff Shafiroff, PhD; and Steven Edelman, MD
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Kali S. Thomas, PhD; Momotazur Rahman, PhD; Vincent Mor, PhD; and Orna Intrator, PhD

Switching from Multiple Daily Injections to CSII Pump Therapy: Insulin Expenditures in Type 2 Diabetes

Guy David, PhD; Max Gill, MBA, Candace Gunnarsson, EdD; Jeff Shafiroff, PhD; and Steven Edelman, MD
The effect of switching from multiple daily insulin injections to an insulin pump on insulin and other diabetic drug expenditures in type 2 diabetes.
ABSTRACT
Objectives
To identify variations in expenditures and utilization of insulin and other antidiabetes medications by comparing patients with type 2 diabetes mellitus using continuous subcutaneous insulin infusion (CSII) pump therapy versus multiple daily injection (MDI) therapy.

Study Design
Truven Health Analytics MarketScan Commercial Claims and Encounters Database and Medicare Supplemental Database for 2006 to 2010 were used in a difference-in-differences approach that took advantage of variation in the timing of the switch from MDI therapy to CSII pump therapy.

Methods
Continuous users of MDI therapy throughout the study period were compared with those who switched to the CSII pump therapy during this period. Specifications included: coefficient estimates from cross-sectional ordinary least squares (OLS) regressions with: 1) no additional controls, 2) controls for patient demographics and comorbidities, and 3) patient fixed effects. Propensity score matching at baseline mitigated concerns regarding patient selection bias.

Results
While insulin expenditures rose during the study period, switching to CSII pump therapy led to sizable reductions in insulin expenditures. This reduction in insulin expenditures due to switching varied between $657 (standard error [SE] $126; P <.01) and $1011 (SE $250.60; P <.01) per year.

Conclusions
This study demonstrated a significant reduction in insulin expenditures among MDI patients who switched to CSII pump therapy at various times throughout the study period.

Am J Manag Care. 2014;20(11):e490-e497
The primary objective of this study was to identify the impact of switching from multiple daily injections (MDIs) to continuous subcutaneous insulin infusion (CSII) pump therapy on insulin and other antidiabetic medication expenditures in individuals with type 2 diabetes mellitus.
  • This study demonstrated a significant reduction in insulin expenditures among MDI patients who switched to CSII pump therapy throughout the study period.
  • While insulin expenditures rose during the study period (as shown in Figure 1), switching to CSII pump therapy led to sizable reductions in insulin expenditures.
  • This reduction in insulin expenditures due to switching varied between $657 (SE $126; P <.01) and $1011 (SE $250.60; P <.01) per year.
As the prevalence of diabetes rises in the United States, managing the costs associated with treating the disease and its complications is a vexing issue for government and commercial payers. According to 2011 data from the CDC, 25.8 million Americans have diabetes, representing 8.3% of the population. The total cost of diagnosed diabetes reached $174 billion in the United States in 2007: $116 billion was direct medical expenditures, and $58 billion was indirect costs tied to disability, work loss, and premature mortality.1

As 90% to 95% of diagnosed cases of diabetes are type 2 diabetes mellitus (T2DM), stakeholders are seeking solutions to its increasing incidence.2 Complementing pharmacologic and traditional insulin treatments is the continuous subcutaneous insulin infusion (CSII) device, commonly known as the insulin pump. CSII pump therapy is an option for the T2DM population, but it has largely been the domain of the type 1 diabetes mellitus (T1DM) population.3-5 In a 2008 article, Pickup et al noted that limited work has been conducted on the use of CSII pump therapy in patients with T2DM and that more clinical studies are needed.6 More recently, a 2010 consensus statement from the American Association of Clinical Endocrinologists made a similar observation.7 Research by Reznik and Cohen stated that use of the CSII pump is a fairly recent therapy for T2DM as compared with T1DM, and few countries allow for reimbursement in patients with T2DM.8

The relatively small use of CSII pump therapy among patients with T2DM may reflect the fact that the effectiveness of the pump, compared with multiple daily injections (MDIs) of insulin, has not been well established for this population. 9 Few randomized clinical trials or systematic reviews have been conducted comparing the clinical efficacy of the 2 treatments in this population, and results are inconclusive.10 While some studies have found CSII pump therapy superior to MDI therapy in terms of reducing glycated hemoglobin11 and providing better metabolic control,12 others have reported no statistically significant differences between the two.13-15

One obstacle to greater CSII pump therapy in patients with T2DM is the challenging set of Medicare guidelines for reimbursement. Specifically, Medicare beneficiaries must demonstrate substantial evidence of insulin deficiency, such as a documented fasting C-peptide level ≤110% (or ≤200% if renal insufficiency is present) at the lower limit of normalof the laboratory’s measurement method with a concurrent fasting blood glucose ≤225 mg/ dL, 6 months of MDI therapy, and other clinical factors.16,17 An estimated 26.9% of the Medicare population has diagnosed or undiagnosed T2DM1; yet, possibly due to reimbursement restrictions, insulin pump usage in this T2DM cohort remains limited.

As payers continually seek to contain costs related to the growing T2DM population, finding ways to reduce spending could be meaningful. One way may be by lowering the insulin deficiency requirement. Only a few studies have examined this possibility. However. In a study of 56 insulin-naïve T2DM patients, Edelman et al found that for those who switched to CSII pump therapy, after 16 weeks, the mean and SD total daily insulin dose was 95 + 59 U and there was significant improvement in glycemic control.18 Wolff-McDonagh et al performed an evaluation of insulin use in 15 adults with poorly controlled T2DM.19 Before CSII pump therapy initiation, patients had been using MDI therapy for at least 1 year with or without oral glucose-lowering and/or sensitizing agents. Once CSII pump therapy use began, a significant reduction in basal insulin use was found at 1 year. Over a hypothetical, projected 4-year period, subjects requiring more than 150 units daily realized a savings of $12,274 in insulin and CSII pump therapy costs compared with MDI therapy However, subjects in the moderate and low-use insulin group had an increase in costs.

The primary objective of this study was to identify the impact of switching from MDI therapy to CSII pump therapy on insulin and other antidiabetes medication expenditures in individuals with T2DM. As this study assesses changes in expenditures linked to utilization of insulin and other antidiabetes medications, any differences among the cohorts could have reimbursement implications for payers.

METHODS

Data Source

This study analyzed data from the US MarketScan Commercial Claims and Encounters Database and Medicare Supplemental Database from Truven Health Analytics (New York, New York).20 The MarketScan databases are constructed of de-identified patient-level records from 170 million unique patients, collected since 1995 from health plans, employers, and state Medicaid agencies. In particular, they include data from 300 contributing employers and 25 contributing health plans, and have been used in a variety of diabetes-related studies.21-23

A protocol describing the study objectives, criteria for patient selection, data elements of interest, and statistical methods were submitted to the New England Institutional Review Board (NEIRB) and were deemed exempt from review (NEIRB #12-348).

Study Population

Patient-level data were extracted from the 2 MarketScan databases, covering the period between January 2006 and December 2010. There were 3,825,352 patients with commercial insurance and 1,215,141 patients with Medicare who were identified by an algorithm as T1DM or T2DM patients. To be included in the analysis, T2DM patients had to be continuously enrolled in a health plan and have prescription drug coverage for the entire sample period.

For each year, patients were classified as either MDI therapy (n = 6372) or CSII pump therapy (n = 181) patients. MDI patients were those having a record of 2 or more rapid- or short-acting insulin prescriptions as well as 2 or more long-acting insulin prescriptions in each year. CSII pump therapy patients were identified as having the following Healthcare Common Procedure Coding System codes: E0784 (durable pump) or A9274 (disposable pump), along with CSII pump therapy supplies A4230, A4232, and A4231. Patients with continuous insulin pump use for the entire time period were excluded (n = 1455). In this analysis, expenditures include insulin and antidiabetic medications only; insulin supplies are not included in expenditures.

Once the mode of treatment was identified, patients were divided into cohorts based on their mode of insulin use. Of particular interest were patients classified as users of MDI therapy for all 5 sample years (continuous MDI patients) as well as patients classified as users of MDI in 2006 who switched to CSII pump therapy by 2010 (switchers). The switchers group included 4 switching patterns based on the year in which the switch occurred. The final sample contained 4490 commercially insured and 2063 Medicare patients classified as T2DM patients with continuous health plan and prescription coverage for all 5 years. Of these 6553 patients, 6372 were continuous MDI patients and 181 were switchers. No switchers were available among Medicare patients since the Medicare coverage policy effectively restricts pump access for T2DM patients.

Statistical Analysis

To study the impact of switching from MDI to CSII pump therapy on insulin expenditures and other antidiabetes medications expenditures, the following regression model specification was used: 

   ∆EXPit= β1 + β2 × Switchi + β3 × Yeart + β4

       × [Switchi × Pumpit] + g × Xit + eit

This specification, frequently used in economics and health services research, compares T2DM patients in the year following the switch with both themselves prior to the switch and with patients who stayed on MDIs in that year (the control group). Since patients switched in different years, the control group consisted of patients who never switched (continuous MDI patients) and patients who switched in subsequent years (switchers).

The dependent variable, EXPit, corresponds to 2 distinct dependent variables: the change in annual insulin-related expenditures and the change in annual expenditures for other antidiabetes medications. Switchi is an indicator variable equal to 1 for patients in the switchers category and 0 for nonswitchers. This indicator is designed to capture differences between continuous MDI patients and switchers even in periods when both groups are on MDIs. Since the effect of switching is identified from its timing, it is crucial tocontrol for overall trends affecting all patients in the sample. Yeart captures such longitudinal effects. [Switchi × Pumpit] is an interaction-based time indicator for patient i (equal to 1 in the year post switching and 0 in pre-switching periods). This indicator is designed to capture differences between the pre and post periods for each individual switcher. This interaction of timing and treatment captures the effect of switching from MDI therapy to CSII pump therapy on patient drug expenditures. A negative and significant b4 would imply a reduction in drug expenditures associated with switching from MDI therapy to CSII pump therapy.

Propensity score matching was used to select a subset of patients for analysis that would be as similar as possible to each other. Since not all 181 patients who switched are similar in terms of clinical covariates to those who did not switch, we were able to match 177 patients using propensity scores generated from a multivariable logistic regression with stepwise selection. Propensity scores from the same multivariable logistic regression without stepwise selection were used to match an additional 151 pairs. In this regression, all variables remained in the model regardless of their significance level.

RESULTS

Clinical and demographic characteristics of the study population at baseline are summarized for continuous MDI patients and switchers (Table 1). This comparison was performed for the entire sample (n = 6553) and the 2 matched samples, 151 pairs in Table 1 and 177 pairs in eAppendix Table A (available at www.ajmc.com). In the entire population, continuous MDI patients were more likely than switchers to be older (aged 56.2 vs 43.1 years), female (43% vs 41%), and have certain comorbidities, such as heart failure (7% vs 2%) and hypertension (38% vs 20%). Differences in comorbid conditions between Medicare patients and younger patients mostly disappeared in the matched samples. Antidiabetes medication expenditures for patients with T2DM between 2006 and 2010 were fairly flat, but the average patient experienced a 70% increase in insulin expenditures during the same period (Figure 1).

 
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