Study of the effect of prior calorie intake on results of random blood sugar measurement for screening of diabetes mellitus

Background: Random blood sugar (RBS) is a commonly performed screening test for type 2 diabetes in both programmatic as well as clinical settings. Previous calorie intake is known to affect the results of RBS. So, present study was conducted to assess the effect of previous calorie intake on sensitivity, specificity, positive and negative predictive values (NPV) and accuracy of RBS.Methods: A cross sectional study was done in 317 patients of 30 years or more using systematic random sampling in a general outpatient department of a district hospital. All the patients underwent RBS measurement. History of calorie intake in past 1-2 hours before undergoing RBS was taken. Screening test parameters of RBS was evaluated using oral glucose tolerance test as clinical reference.Results: This study found that calorie consumption of 200 kcal or more significantly affected the screening test result of RBS. When patient had consumed 200 kcal or more in last 1-2 hours, the sensitivity of RBS is 90.0%, specificity is 57.4%, positive predictive value (PPV) is 26.9% and NPV is 97.1%. Whereas, these parameters are 63.3%. 78.5%, 43.6% and 88.9% respectively when patient had consumed less than 200 kcal in last 1-2 hours before RBS.Conclusions: Sensitivity and NPV of RBS is higher if patient had consumed more than 200 kcal 1-2 hours prior to RBS whereas specificity and PPV is higher if patient had consumed less than 200 kcal. Taking history of quantity and time of last meal would be helpful to better interpret the screening test results of RBS.