The results of random plasma glucose (RPG) tests, which are commonly measured as part of routine outpatient laboratory testing, could help physicians identify individuals at high risk for type 2 diabetes for screening earlier than is done in current practice, according to research published online this week in the journal PLOS ONE.

“We found that RPG levels below the recommended diabetes diagnostic range, but higher than levels in patients who remained diabetes-free, were highly predictive of a future diabetes diagnosis,” says first author Mary Rhee, MD, associate professor of medicine at Emory University School of Medicine and a physician at the Atlanta Veterans Affairs Health Care System. “Using this test, which is available as part of routine blood tests ordered during or after physician visits, could signal the need for further testing and lead to earlier identification and treatment of diabetes and to preventive interventions before disease onset in those found to have prediabetes.”

A research team from Emory University and the Atlanta VA Health Care System led a retrospective study of data from 942,446 US veterans without diagnosed diabetes. The data came from the Veterans Administration Corporate Data Warehouse (CDW). The CDW contains data on all veterans receiving care in Veterans Health Administration facilities nationwide, including demographics, vital signs, laboratory tests, diagnoses, procedures, and prescriptions. If veterans were over age 65, their data were complemented with data from the Centers for Medicare and Medicaid Services (CMS) databases.

Study subjects had three or more RPG measurements available in the first year of the study, and each had at least one primary care visit each year during 5 years of follow-up. Over the 5 years, 94,599 participants were diagnosed with diabetes, while 847,847 were not. Baseline demographics in the diagnosed and non-diagnosed groups were similar, except the diagnosed patients had higher body mass index, higher RPG readings, and were more likely to be African-American. Patients with at least two RPG measurements of 115 mg/dL or higher within 12 months were highly likely to be diagnosed with diabetes within a few years. A glucose level of 130 mg/dL was even more predictive of diabetes.

The study’s authors included Lawrence Phillips, MD, professor of medicine at Emory University School of Medicine and a physician at the Atlanta VA Health Care System, and Peter Wilson, MD, Emory professor of medicine and a physician at the Atlanta VA Health Care System. The research team also included investigators at MAVERIC VA Boston Healthcare System, VA Eastern Colorado Healthcare System, University of Colorado School of Medicine, Brigham and Women’s Hospital, and Harvard Medical School and School of Public Health.

Type 2 diabetes is a significant public health problem and is the major cause of kidney failure, blindness, and nontraumatic leg amputations in US adults, as well as a leading cause of stroke and heart disease. However, according to the Centers for Disease Control and Prevention, more than seven million Americans with type 2 diabetes are undiagnosed, and the onset of the disease may occur as many as 9–12 years before clinical diagnosis.

According to the authors: “Although RPG levels ≥200 mg/dL (in combination with symptoms) are considered diagnostic, considerably lower levels appeared to confer substantial risk…accordingly, our findings indicate that strong consideration should be given to follow-up diagnostic testing in patients who, within 1 year, have two or more outpatient RPGs that are 115 mg/dL or higher, and especially RPGs that are 130 mg/dL or higher.”

According to the study’s authors, although systematic screening could permit earlier detection at the point when use of lifestyle changes and medications could delay disease progression and reduce diabetes-related complications, many healthcare systems have not yet implemented widespread screening. There has been little previous examination of RPG as a predictor of diabetes. A convenient, inexpensive, readily available way to identify those at high risk for undiagnosed prediabetes or diabetes—such as the RPG test—could help improve standard medical practice, say the authors.

The study was funded by the Veterans Affairs Health Care System.