Validity of glycated haemoglobin to diagnose new onset diabetes after transplantation

Abstract

Diagnosing new onset diabetes after transplantation (NODAT) by glycated haemoglobin (HbA1c) has not been validated against the gold-standard oral glucose tolerance test (OGTT). We analysed the predictive and optimum value of HbA1c to diagnose NODAT amongst nondiabetic renal transplant recipients. Assessment of glucose metabolism (OGTT and HbA1c) was prospectively undertaken at 3 and 12months post-transplantation in 71 nondiabetic renal transplant recipients. Receiver operator characteristic (ROC) curve analyses were performed to determine accuracy, sensitivity, specificity and area under curve (c-statistic). Incidence of NODAT at 3 and 12months post-transplantation was 14.3% and 9.5% respectively. At 3months, optimum HbA1c cut-off value for predicting NODAT based on fasting glucose was 7.35 [AUC 1.00 (sensitivity 100.0%, specificity 100.0%, P=0.004)] and for postprandial glucose-defined NODAT was 6.20 [AUC 0.98 (sensitivity 100.0%, specificity 88.9%, P<0.001)]. At 12months, optimum HbA1c cut-off value for both fasting- and postprandial glucose-defined NODAT was 6.45 [AUC 0.92 (sensitivity 100.0%, specificity 87.5%, P=0.048) and AUC 0.84 (sensitivity 75.0%, specificity 89.5%, P=0.026) respectively]. Concordance between diagnosis of NODAT (OGTT+, HbA1c+) and nondiagnosis of NODAT (OGTT-, HbA1c-) was 88.9% and 98.7% respectively. To conclude, HbA1c (≥6.5%) can be utilized to diagnose NODAT beyond 3months post-transplantation but the OGTT remains the gold-standard tool.