Heat in the Arabian Gulf: An analytical review of the impact of ambient temperature on the oral glucose tolerance test

Abstract

Diabetes mellitus (DM) and gestational diabetes (GDM) are often diagnosed and their long-term progression monitored either by a fasting blood glucose test (FGT) or an oral blood glucose tolerance test (OGTT). These tests are well-standardized and are conveniently carried out via blood samples drawn from the patient's arm, which are later analyzed to measure blood glucose concentration. Pre-analytical guidelines for laboratory analysis of blood samples intended for the measurement of plasma glucose maintain that the two principal factors which contribute to poor reproducibility of the OGTT are (i) the variable effects of administration of a hyperosmolar glucose solution on gastric emptying, and (ii) the ambient temperature while the blood sample is being captured. Although viewing ambient temperature as a purely random effect may be acceptable for routine diagnostic tests carried out in “the West”, the substantially higher regular temperatures experienced throughout the year by many African, Asian and Middle-Eastern countries suggest that in some locations and circumstances, ambient temperature might be better regarded as a systematic influence on the OGTT. The principal purpose of this short literature review is to highlight the potentially significant influence of ambient temperature (during the blood-draw) on the results of OGTT blood glucose measurements. Physicians and healthworkers should be aware of this phenomenon which not only can affect the diagnoses for particular patients but is also capable of producing a significant impact on subsequent prevalence estimates for both diabetes and gestational diabetes. Further studies should be conducted throughout the Arabian Gulf to elucidate the magnitude of this effect on local populations by making use of well-characterized patients under standardized conditions where temperature and humidity can be strictly controlled.