Do Diabetes Group Visits Do Diabetes Group Visits Lead to Lower Medical Care Lead to Lower Medical Care

Charges?Charges?Kathryn Marley Magruder, PhD, MPHKathryn Marley Magruder, PhD, MPH

VA Medical CenterVA Medical Center

Medical University of South CarolinaMedical University of South Carolina

Charleston, South CarolinaCharleston, South Carolina

Funded by:Funded by:

Robert Wood Johnson FoundationRobert Wood Johnson Foundation

Agency for Healthcare and QualityAgency for Healthcare and Quality

Dawn E. Clancy, MD, MSCRDawn E. Clancy, MD, MSCR

Clara E. Dismuke, PhDClara E. Dismuke, PhD

Kit N. Simpson, DrPHKit N. Simpson, DrPH

David Bradford, PhDDavid Bradford, PhD

BackgroundBackground

Efficient and effective care for patients Efficient and effective care for patients with type 2 diabetes (DM) consistent with with type 2 diabetes (DM) consistent with American Diabetes Association (ADA)American Diabetes Association (ADA)

Group Visits (GVs) improve efficiency and Group Visits (GVs) improve efficiency and throughput of patients by increasing throughput of patients by increasing access and decreasing backlogs of access and decreasing backlogs of patients awaiting appointments.patients awaiting appointments.

Previous managed care studies reveal Previous managed care studies reveal GVs less costly and at least as effective GVs less costly and at least as effective as usual care for quality; review of the as usual care for quality; review of the literature does not find they substantially literature does not find they substantially reduce costs for individuals with DM.reduce costs for individuals with DM.

RationaleRationale

Research on GVs remains in its Research on GVs remains in its infancy.infancy.

Over a dozen articles exist describing Over a dozen articles exist describing GVs but only 6 studies reported are GVs but only 6 studies reported are randomized controlled trials.randomized controlled trials.

None show notable cost results. None show notable cost results.

Study QuestionsStudy Questions

Do GVs for patients with type 2 Do GVs for patients with type 2 diabetes lower healthcare utilization diabetes lower healthcare utilization and outpatient (OP) charges?and outpatient (OP) charges?

Is the lack of statistically significant Is the lack of statistically significant findings in previous studies due to findings in previous studies due to endogeneity of the GV variable in endogeneity of the GV variable in cost models?cost models?

Design and SamplingDesign and Sampling

Randomized controlled clinical trialRandomized controlled clinical trial 506 uncontrolled type 2 diabetic patients 506 uncontrolled type 2 diabetic patients

with a HgbA1c > 8.0% invited to with a HgbA1c > 8.0% invited to participateparticipate

186 patients enrolled after signing IRB 186 patients enrolled after signing IRB approved consent documentsapproved consent documents

Patients randomly assigned to participate Patients randomly assigned to participate in group visits or traditional one-on-one in group visits or traditional one-on-one patient-physician visitspatient-physician visits

Data Collection and Data Collection and Key VariablesKey Variables Charges for OP, ED visits, and IP stays Charges for OP, ED visits, and IP stays

collected at study endcollected at study end Distance to provider (living within 10, Distance to provider (living within 10,

20, or 30 miles of the provider);20, or 30 miles of the provider); Charlson scores, ICD-9 based Charlson scores, ICD-9 based

measures of illness severitymeasures of illness severity;; Diagnosis codes; procedure codes.Diagnosis codes; procedure codes.

Statistical AnalysisStatistical Analysis

Mann-Whitney tests used for differences in mean Mann-Whitney tests used for differences in mean charges by service (OP visits, ED visits, and IP stays)charges by service (OP visits, ED visits, and IP stays)

Separate charge models used for OP visits and ED Separate charge models used for OP visits and ED visits (IP stays had too few nonzero observations to visits (IP stays had too few nonzero observations to estimate models reliably)estimate models reliably)

OP visit models include controls for payer, Charlson OP visit models include controls for payer, Charlson score, distance to provider, and a binary indicator of score, distance to provider, and a binary indicator of GV treatmentGV treatment

With charge models, distance to provider (within 10, With charge models, distance to provider (within 10, 20, or 30 miles) used as binary indicators (>30 miles 20, or 30 miles) used as binary indicators (>30 miles omitted as those more likely to use OP services from omitted as those more likely to use OP services from providers whose charges are not captured in our providers whose charges are not captured in our data)data)

Statistical Analysis Statistical Analysis (cont.)(cont.) Estimating the OP charge model using Estimating the OP charge model using

ordinary least squares (OLS), we ordinary least squares (OLS), we hypothesized when unobserved patient hypothesized when unobserved patient characteristics correlate with both the characteristics correlate with both the intervention (GVs) and the outcome intervention (GVs) and the outcome (healthcare costs), endogeneity can bias OLS (healthcare costs), endogeneity can bias OLS resultsresults

In many RCTs, treatment assignment, In many RCTs, treatment assignment, assessment, termination, and dosage are assessment, termination, and dosage are controlled for by the researcher (exogenous), controlled for by the researcher (exogenous), a necessary condition for statistical tests of a necessary condition for statistical tests of between-group differences in patient between-group differences in patient outcomes to be unbiased.outcomes to be unbiased.

Statistical Analysis Statistical Analysis (cont.)(cont.) Study patients, randomized to treatment Study patients, randomized to treatment

modality (GVs or usual care), largely modality (GVs or usual care), largely determined the intensity (dosage) of their determined the intensity (dosage) of their ownown treatment by choosing not to attend treatment by choosing not to attend all GVs or not staying for the entirety of all GVs or not staying for the entirety of any given GVany given GV

This choice, likely affected by the This choice, likely affected by the treatment arm to which the patient was treatment arm to which the patient was randomized, created endogeneity of the GV randomized, created endogeneity of the GV variable in the charge modelvariable in the charge model

Endogeneity can be controlled for by Endogeneity can be controlled for by estimating a treatment effect model based estimating a treatment effect model based on Heckman control functionon Heckman control function

Statistical Analysis Statistical Analysis (cont.)(cont.) Re-estimating the OP charge model using a Re-estimating the OP charge model using a

treatment effect model and simultaneously treatment effect model and simultaneously estimating likelihood of GV participation and OP estimating likelihood of GV participation and OP charges controlled for potential endogeneity. charges controlled for potential endogeneity.

Initial probit model found factors likely to affect Initial probit model found factors likely to affect GV participation to be included in the GV GV participation to be included in the GV participation likelihood equation in the treatment participation likelihood equation in the treatment effect model. effect model.

OLS for the OP charge model revealed the same OLS for the OP charge model revealed the same for the charge equation in the treatment effect for the charge equation in the treatment effect model using drive time as a continuous measure model using drive time as a continuous measure in the GV participation part of the model and in the GV participation part of the model and including payer, Charlson score, and binary including payer, Charlson score, and binary indicators for distance to provider in the OP indicators for distance to provider in the OP charge models.charge models.

ResultsResults Mann-Whitney test results show that GV Mann-Whitney test results show that GV

patients had 34.7% higher OP expenditures, patients had 34.7% higher OP expenditures, 49.1% lower ED expenditures, and 30.2% 49.1% lower ED expenditures, and 30.2% lower total expenditures compared with those lower total expenditures compared with those in control group (in control group (P P <.05 for all).<.05 for all).

Initial OLS with robust standard errors Initial OLS with robust standard errors estimates of the unadjusted OP charge model estimates of the unadjusted OP charge model revealed statistically significant effects of GV revealed statistically significant effects of GV treatment on OP care initially estimating that treatment on OP care initially estimating that GV treatment increased OP costs by GV treatment increased OP costs by $699.52/patient/year$699.52/patient/year

Results (cont.)Results (cont.) Though there was a statistically significant Though there was a statistically significant

and marginally positive effect on GVs in the and marginally positive effect on GVs in the OP cost model that did not correct for OP cost model that did not correct for endogeneity, the treatment effect model endogeneity, the treatment effect model showed a statistically significant marginally showed a statistically significant marginally negativenegative effect of GV treatment on OP effect of GV treatment on OP charges of $3065.47.charges of $3065.47.

To understand how GV treatment reduced OP To understand how GV treatment reduced OP charges, we estimated a treatment effect charges, we estimated a treatment effect model of specialty care visits and found that model of specialty care visits and found that GV treatment leads to a reduction of 4.15 GV treatment leads to a reduction of 4.15 specialty care visits/GV patient/year.specialty care visits/GV patient/year.

SummarySummary

In our study of GVs for In our study of GVs for inadequately insured patients with inadequately insured patients with type 2 DM, we demonstrate that, type 2 DM, we demonstrate that, after controlling for endogeneity of after controlling for endogeneity of the GV variable, GV treatment the GV variable, GV treatment statistically significantly lowers statistically significantly lowers outpatient charges by decreasing outpatient charges by decreasing specialty care visitsspecialty care visits