Abstract
INTRODUCTION: Transfusion-dependent beta-thalassemia (TDT) leads to iron overload, contributing to glucose intolerance through insulin resistance and pancreatic beta-cell dysfunction. The reliability of HbA1c in diagnosing diabetes mellitus in TDT is questionable due to altered red blood cell dynamics. Fructosamine, reflecting short-term glycaemia, offers a potential alternative. This study assesses the utility of HbA1c and fructosamine in evaluating glucose tolerance in adult TDT patients. METHODS: In this cross-sectional study, 61 adult TDT patients were recruited from a tertiary care centre in North India. Glucose tolerance was assessed using fasting plasma glucose (FPG) and a 2-hour oral glucose tolerance test (2Hr-OGTT) as gold standards. HbA1c and serum fructosamine levels were measured. Sensitivity, specificity, and diagnostic accuracy of these two tests and their correlation with FPG and 2Hr-OGTT were analysed. RESULTS: Among the 61 patients of TDT (median age: 27 years), 63.9% had normal glucose tolerance (NGT), while 36.1% exhibited glucose intolerance (24.6% prediabetes, 11.5% diabetes). HbA1c and fructosamine were significantly elevated in glucose-intolerant patients compared to those with NGT. HbA1c significantly correlated with FPG (rho = 0.42, P < 0.001) and 2Hr-OGTT (rho = 0.319, P = 0.012), whereas fructosamine did not show any correlation with either FPG or 2Hr-OGTT. Using standard cut-offs, HbA1c demonstrated higher sensitivity (86%) but lower specificity (31%) compared to fructosamine (46% sensitivity, 74% specificity). CONCLUSION: While both markers were elevated in glucose-intolerant TDT patients, their diagnostic reliability remains limited. FPG and 2Hr-OGTT remain the gold standard for diagnosing glucose intolerance in TDT.