Fasting Plasma Glucose in the Screening for Type 2 Diabetes in Morbidly Obese Subjects

Abstract

Higher mortality rates among morbidly obese (BMI of > or =40 or > or =35 kg/m2 with weight-related comorbidities) subjects are mainly explained by comorbidities such as type 2 diabetes. As bariatric surgery ameliorates diabetes, obese diabetic subjects will receive great benefits from bariatric surgery. Screening for diabetes prior to surgical referral is therefore crucial. We studied 1,253 consecutively recruited (2005-2008) morbidly obese subjects (67% women). Among subjects without known diabetes, 70% (670/961) performed an oral glucose tolerance test (OGTT). Screen-detected diabetes was defined as fasting plasma glucose (fPG) > or =7.0 mmol/l and/or 2-h glucose concentration (2hPG) > or = 11.1 mmol/l. Within the study population, 31% had diabetes, of which 8% were screen-detected. Eighty percent of those with screen-detected diabetes were diagnosed by fPG. In subjects with nondiabetic fPG concentrations, elevating the fPG cutoff value from 5.2 mmol/l to the World Health Organization's (WHO's) recommended value of 6.1 mmol/l reduced the percentage of the population needing an OGTT considerably (78-23%), but only slightly reduced the sensitivity of fPG in detecting a diabetic 2hPG concentration (100-77%). Only 7% of the patients with fPG between 6.1 and 6.9 mmol/l had a diabetic 2hPG concentration. Following the WHO's recommendations, we found that 95% of all subjects with unknown diabetes were identified. Fasting glucose identified four out of five morbidly obese subjects with unknown diabetes. A supplemental OGTT in selected persons identified the majority of the remaining diabetic cases.