Comparison of fasting glucose and oral glucose tolerance tests in diagnosis of diabetes mellitus in liver cirrhosis

Background: Diabetes mellitus (DM) and glucose intolerance are commonly associated with liver cirrhosis and considered as important prognostic factors in liver cirrhosis. Objective: To determine the more sensisitive test for diagnosis of diabetes mellitus in liver cirrhosis. Methods: A total of 92 patients with liver cirrhosis were enrolled in a descriptive-analytic study. The levels of FBS and blood sugar two hours after ingestion of 75gr glucose (OGTT) were measured. FBS and 2-hPG concentrations were analysed for all subjects. Chi-square test and Fisher's exact test were used to analyse the data and p values <0.05 were considered as significant. Findings: A total of 92 cirrhotic cases with mean age of 54.1±14.1 years were enrolled in this study of which 51 cases were males (55.4%) and 41 females (44.6%). Using FBS measurement test, DM was diagnosed in 14 subjects (15.2%), impaired fasting glucose (IFG) in 16 subjects (17.4%), and normal fasting glucose in 62 subjects (67.4%). However, when OGTT was employed, DM found to be present in 36 subjects (39.1%), impaired glucose tolerance (IGT) in 26 subjects (28.3%), and normal glucose tolerance (NGT) in 30 subjects (32.6%). Comparison of FBS and OGTT (as gold standard test) showed that there was a significant difference between two tests (p<0.001). The sensitivity of FBS test to diagnose DM was 46.7% with a specificity of 96.7 %. The P.P.V and NPV were 96.7% and 46.7%, respectively. The FBS cut off was estimated at 83.50 mg/dl. Conclusion: The determination of FBS level seems to be insufficient in detecting DM in patients with liver cirrhosis. Thus, in addition to FBS measurement, the OGTT, as a routine test for cirrhosis, is recommended.