Prediabetes cases are on the rise in the United States. At least 84 million adults have it, but most aren’t aware of their condition, writes Deborah Levenson in the September issue of Clinical Laboratory News. Screening patients might encourage them to make better lifestyle choices or take medications to ward off diabetes. The problem is there’s no consensus on how to define prediabetes. The World Health Organization (WHO), American Diabetes Association (ADA) and International Expert Committee (IEC) all have different criteria and thresholds for this condition, based on fasting glucose concentration (FG) and 2-hour glucose (2HG) testing and HbA1c results.

“The varying definitions cause confusion for patients and physicians and have different sensitivities, specificities, and morbidity and mortality hazard ratios. They also identify different groups of people,” Levenson writes, citing various studies to illustrate this point.

This discordance makes it especially difficult to figure out who’s eligible for prevention programs, Elizabeth Selvin, PhD, MPH, professor of epidemiology and medicine at Johns Hopkins Bloomberg School of Public Health and School of Medicine in Baltimore tells CLN.

“Further, the three methods of measuring glucose control for diagnosis capture different aspects of glucose homeostasis, so an individual deemed to have prediabetes by one method might not be by another,” Levenson writes.

One study of Selvin’s that compared outcomes risk for prediabetes among 10,000 black and white Americans over a decade’s time, reported very different results under HbA1c-based and glucose-based definitions. “HbA1c-related definitions resulted in lower prevalence estimates than WHO and ADA cutoffs for FG and 2HG. Meanwhile, ADA FG and WHO 2HG-based definitions of prediabetes were more sensitive for long-term outcomes,” Levenson summarizes.

Depending on the prediabetes criteria, a patient may be at higher risk for certain comorbidities such as chronic kidney or cardiovascular disease, or more likely to be black, female, and obese.

Labs and clinicians looking for the best prediabetes tests aren’t going to find easy answers, Eleanor Barry, MBBS, MRCP, MRCGP, a general practitioner and National Institute for Health Research in Practice fellow at the University of Oxford’s Nuffield Department of Primary Care Health Sciences in the United Kingdom, tells CLN. “Each test is associated with a different pathological process which leads to diabetes and cardiovascular disease,” she explains.

Perhaps the answer is to use both glucose and HbA1c testing in at-risk patients, experts suggest. Selvin advises that labs explain the respective strengths and weaknesses of prediabetes to clinicians: that anemias can interfere with HbA1c, or that FG has a high degree of preanalytic variability.

WHO’s plans to update diabetes guidelines and review treatment interventions will hopefully provide some needed guidance on prediabetes care, Selvin believes.

Pick up September’s CLN to gain additional insights on the variations among prediabetes definitions and testing methods.