Impaired glucose regulation in adults in Jamaica: who should have the oral glucose tolerance test?

OBJECTIVE To compare the 1999 World Health Organization (WHO) fasting plasma glucose (FPG) criteria and the WHO 2-hour post-challenge glucose (2hPG) criteria during an oral glucose tolerance test (OGTT) in identifying adults in Jamaica with hyperglycemia. As the OGTT is not commonly used in clinical practice, factors associated with the failure of the FPG criteria to detect persons with impaired 2hPG were investigated. METHODS A random sample of 2 096 adults, 25-74 years old, living in the town of Spanish Town, Jamaica, was evaluated for diabetes. After excluding 215 individuals for reasons such as missing data, the remaining 1 881 persons were composed of 187 who were previously known to have diabetes and 1 694 who were screened for diabetes with both FPG and 2hPG. RESULTS The FPG criteria detected 83 cases of diabetes, compared to 72 by the 2hPG criteria. The kappa statistic comparing the two criteria was 0.31 (95% confidence interval: 0.28-0.34), indicating fair agreement. There were 261 cases of impaired glucose tolerance (IGT) and 92 cases of impaired fasting glucose (IFG). In those 92 with IFG, an OGTT would identify 34 cases of IGT and 14 cases of diabetes. Of those classified as normoglycemic by FPG criteria, 14% of them had IGT or diabetes by 2hPG criteria. The factors predicting the likelihood of non-detection of impaired glucose tolerance or diabetes by FPG were age, body mass index, central obesity, systolic blood pressure, and female sex. By receiver operating characteristic curve analysis, an FPG of 5.1 mmol/L would predict a 2hPG >/= 7.8 mmol/L. CONCLUSIONS A few individuals classified as normal on FPG will have IGT or diabetes, and an OGTT will be needed to identify them. The yield of IGT detected by screening in Jamaica can be improved by lowering the threshold for IFG or by using clinical information to identify high-risk individuals.