A Comparative Study of Oral Glucose Tolerance Test and Glycated Haemoglobin in High Risk Patients for Diabetes Mellitus

Aims: To ascertain which is a better screening test to diagnose diabetes mellitus, OGTT or HbA1c. Method : 100 high risk patients for diabetes and 35 controls (none a known diabetic) were screened by OGTT and HbA1c. 1980 WHO criteria for diagnosing diabetes and HbA1c 3 7% (cation exchange chromatography) were followed to categorise patients as diabetics. Results : 17% of the patients were hound to be diabetic by OGTT criteria and 49% by HbA1c criteria. Sensitivity and specificity of OGTT and HbA1c (3 7%) were 24.5%, 90.2%, 89.5%, 56.6% respectively. Besides essential hypertension and obesity coronary artery disease and central obesity have been found to be significantly associated with diabetes. Conclusion : HbA1c is a more sensitive screening test than OGTT, but lacks specificity. OGTT is more specific. All high risk patient should be screened by HbA1c and if HbA1c is 3 7%, they should undergo an OGTT to confirm the diagnosis.