Higher Pretransplantation Hemoglobin A1c Is Associated With Greater Risk of Posttransplant Diabetes Mellitus

INTRODUCTION: Posttransplantation diabetes mellitus (PTDM) is a common complication among kidney transplant recipients and is associated with a higher risk of cardiovascular events and poorer graft and patient survival. The association of pretransplantation hemoglobin A1c (HbA1c) with PTDM remains unclear. Identifying recipients at greatest risk for PTDM may help guide monitoring and treatment strategies to prevent or delay the onset of PTDM. METHODS: We analyzed data from 1499 nondiabetic primary kidney transplant recipients with available pretransplantation HbA1c values in the United States Renal Data System (USRDS) from 2005 to 2011. Recipients with pretransplantation diabetes diagnosis or HbA1c ≥ 6.5% were excluded. We assessed the association of pretransplantation HbA1c with PTDM using Cox proportional hazards models. Pretransplantation HbA1c level as a continuous variable was modeled using restricted cubic splines with knots at the 25th, 50th, and 75th percentiles. Based on results from this model, pretransplantation HbA1c was further modeled using a linear spline with a single knot at 5.4%. RESULTS: A total of 395 recipients (26.4%) developed PTDM over a median follow-up of 1.8 years. Pretransplantation HbA1c was not significantly associated with risk of PTDM below 5.4%, whereas each 1% higher HbA1c above 5.4% was associated with an adjusted hazard ratio of 1.84 (95% confidence interval = 1.28, 2.66; P for change in slope = 0.04). DISCUSSION: Higher pretransplantation HbA1c above 5.4% is independently associated with greater risk of PTDM among kidney transplant recipients. A continuous relationship between pretransplantation HbA1c and risk of PTDM suggests that increased risk starts at HbA1c levels well below current thresholds for prediabetes.