Screening for new-onset diabetes after kidney transplantation: limitations of fasting glucose and advantages of afternoon glucose and glycated hemoglobin.

The sensitivity of fasting plasma glucose (FPG) in screening for new-onset diabetes after transplantation (NODAT) has been questioned, particularly in the presence of moderate-dose prednisolone, where peak plasma glucose occurs 7 to 8 hr after administration. Oral glucose tolerance testing (OGTT) has been mooted as an alternative but is inconvenient for patients. We compared sensitivity of screening tests for NODAT at 6 weeks, 3 months, and 12 months after kidney transplantation in recipients receiving prednisolone, mycophenolate, and tacrolimus. At 6 weeks, NODAT (capillary blood glucose [CapBG] ≥11.1 mmol/L, FPG ≥7.0 mmol/L, 2-hr plasma glucose ≥11.1 mmol/L, or glycated hemoglobin [HbA1c] ≥6.5%) was detected in 46% with CapBG versus 12% with OGTT (P=0.013), 4% with HbA1c (P<0.001), and 0% with FPG (P<0.001; n=26). At 3 months, NODAT was present in 14% with HbA1c versus 20% with OGTT (P=0.600) and 2% with FPG (P=0.059; n=50), whereas, at 12 months, NODAT was found in 4% with HbA1c versus 6% with OGTT (P=1.00) and 2% with FPG (P=0.618; n=51). Combining 3- and 12-month data, OGTT recorded NODAT in 14% and impaired glucose tolerance in 28%, whereas HbA1c detected NODAT in 10% and impaired glucose tolerance (from ≥5.7 to <6.5%) in 51%. Employing HbA1c as a screening test and reserving OGTT for those with impaired glucose tolerance would detect NODAT with a sensitivity more than 94%, avoiding the need for OGTT in 49% of patients. This study confirms the inadequacy of FPG screening for NODAT in the first 6 weeks after transplantation, at which time 4 p.m. CapBG also outperformed OGTT. From 3 months, HbA1c had similar sensitivity to OGTT and represents a convenient alternative.