Opportunistic Screening for Prediabetes and Early Diabetes in Primary Care

People who might have prediabetes or unrecognized diabetes will be screened for these problems at an outpatient visit. For screening, they will take a sugary drink containing 50 grams of glucose, and have a blood sample one hour later. The blood sample will be tested for glucose and A1c (a measure of blood glucose over the previous two months). They will also fill out questionnaires that ask about their health history and how they would feel about exercising and trying to lose weight if they are found to have prediabetes or diabetes. At a subsequent visit, they will have an oral glucose tolerance test (OGTT) - a blood sample, then a sugary drink containing 75 grams of glucose, and a repeat blood sample 2 hours later. We will evaluate the costs of finding out if people have prediabetes or diabetes. For people who are found to have these problems, we will also evaluate how well their doctors treat these problems.

RELEVANCE TO VETERANS' HEALTH: Lack of a good strategy to identify prediabetes - probably \~10 years prior to the development of diabetes that is recognized clinically - may be the greatest present impediment to diabetes care. We are developing a new way to screen for prediabetes, and it should constitute a major opportunity to improve the health of \~4 million veterans; early recognition of glucose intolerance would permit institution of preventive strategies which are efficacious, convenient, and cost-effective - improving the health of individual veterans, reducing diabetes-related health care resource use and costs for the VA, and helping to spare VA funds for management of other disorders. BACKGROUND: Prediabetes is a major public health problem which confers risk of diabetes and cardiovascular disease (CVD), but veterans with prediabetes are not detected, and cannot receive interventions to reduce their risks; CVD events, health resource use, and cost all rise before diabetes is diagnosed. Diabetes can be prevented or delayed by lifestyle change or medication, but since we do not identify prediabetes, glucose intolerance progresses for 5-10 years, and many patients have early diabetes complications and increased CVD risk when they are finally recognized. We are developing a new screening test for prediabetes, a "glucose challenge test" (GCT): patients have a 50g oral glucose challenge at any time of day, regardless of meal status, with a single 1 hr sample. If the GCT exceeds a cutoff, they have a 75g oral glucose tolerance test after an overnight fast, with 0 and 2 hr samples (OGTT). Our GCRC-based Preliminary Data show ROC AUC 0.83 (70% specificity, 82% sensitivity) and $51 per case identified; the GCT should constitute an effective, convenient, inexpensive, cost-effective screen for prediabetes - a critical indicator of individual, VA health care system, and societal risk. OBJECTIVES: To translate our findings into improved health for VA patients, the GCT will need to be implemented in VA primary care settings - where practitioners often do not screen for prediabetes, or manage diabetes optimally. Such barriers must be overcome in order to conduct definitive studies aimed to show that use of the GCT to detect prediabetes (and previously unrecognized diabetes) in primary care leads to improved outcomes. Thus, VA policies for system-wide implementation of GCT screening must be preceded by logical next steps: validation and demonstration of likely cost-effectiveness. METHODS: AIM #1. Validation: (A) To establish feasibility, we will interact with VA primary care providers to solve logistical problems, and determine optimal screening strategies. (B) To assess test performance, we will (a) perform GCTs and measure A1c in \~1,800 patients, (b) evaluate OGTTs in all subjects, and (c) compare sensitivity, specificity, and ROC curves from GCT vs. A1c or "predictive model" screening in primary care to those in our GCRC studies. Availability of this dataset will also permit (d) subsequent management of diabetes/prediabetes to be evaluated relative to standardized guidelines. AIM #2. Costs: To evaluate impact, we will (a) capture the costs of diagnostic tests, staff effort, and patient time; (b) express cost per case identified from both VA health system and societal perspectives; and (c) compare GCT vs. alternative strategies with a wide range of assumptions about false-(+)/false-(-) costs to reflect downstream cost implications of test imperfections. Engagement with this process will also provide (d) for those study patients with prediabetes who go on to develop diabetes, an opportunity to explore VA resource use and costs before and after the diagnosis of diabetes. This will provide preliminary data for subsequent proposals to compare resource use and costs vs. those of other VA patients who are newly diagnosed with diabetes in settings where there is no screening for prediabetes.