Evaluation of HbA1c and fasting plasma glucose for the diagnosis of post-transplant diabetes mellitus and prediabetes in renal transplant recipients
Background: Diabetes mellitus after renal transplantation (PTDM) is a frequent complication and if not timely diagnosed may result in life-threatening microvascular complications. Fasting plasma glucose (FPG) test is considered preliminary screening tool while oral glucose tolerance test (OGTT) is a ‘benchmark test’ for the screening of DM and prediabetes in PTDM. HbA1c test is also now being considered as a most convenient diagnostic tool for Type 2 diabetes mellitus and prediabetes. Therefore, current study was undertaken to evaluate HbA1c and FPG tests for the diagnosis of diabetes and prediabetes by taking OGTT as a gold standard.
Patients and methods: In this prospective study, total 40 renal transplant recipients were recruited from Jinnah and Mayo Hospitals Lahore from January to August 2012. The participants aged ≥18 years who underwent renal transplants more than 3 months ago with no prior history of diabetes mellitus were included. Blood samples were obtained for FPG, OGTT and HbA1c tests according to standard guidelines. Based on ADA thresholds of OGTT, patients were categorized into three groups: 1) DM; 2) prediabetes, and 3) normal plasma glucose levels.
Results: Hyperglycemia was seen in 22 (55%) patients including 6 (15%) with PTDM and 16 (40%) with prediabetes based on OGTT. High value of AUC of FPG (0.8469 p<0.001) vs. AUC of HbA1c (0.7257 p=0.0012) proved that it had relatively more diagnostic potential for early detection of prediabetes in RTR. Similarly, FPG had more AUC (0.8079, p<0.001) value vs. HbA1c AUC (0.7272, p=0.0005) value for screening of PTDM in RTR. Although, the specificity of both the tests were the same (25%). However, FPG was more sensitive (81.25%) as compared to HbA1c (51.52%).
Conclusions: FPG performs as a better screening tool for PTDM and prediabetes; and ADA proposed screening criteria of HbA1c is relatively less sensitive in RTR for local population. A combined use of both tests would be a more appropriate approach for the quick screening of PTDM and prediabetes in RTR.