Fasting plasma glucose and glycosylated hemoglobin in the screening for diabetes mellitus after renal transplantation.

BACKGROUND: Fasting plasma glucose (fPG) is recommended to identify new-onset posttransplant diabetes mellitus (PTDM), but an oral glucose tolerance test (OGTT) has higher diagnostic sensitivity. We aimed to assess the accuracy of fPG and glycosylated hemoglobin (HbA1c) for the selection of patients who should undergo a diagnostic OGTT 10 weeks after renal transplantation.

METHODS: A total of 1571 renal transplant recipients without prior diabetes underwent an OGTT 10 weeks after transplantation. Receiver operating characteristic analyses were used to identify optimal thresholds to incite further diagnostic tests. A sensitivity level of 80% was chosen for screening purpose.

RESULTS: We diagnosed PTDM in 213 (14%) patients of whom 109 (51%) were identified by 2-hr plasma glucose more than or equal to 11.1 mmol/L alone, 35 (17%) by fPG alone, and 69 (32%) by both criteria. Receiver operating characteristic analysis revealed an area under the curve of 0.761 (95% confidence interval 0.714-0.809) for fPG and 0.817 (95% confidence interval 0.758-0.876) for HbA1c. Performing an OGTT on patients with an fPG more than or equal to 5.3 mmol/L or HbA1c more than or equal to 5.8% predicted diabetes with 81% and 83% sensitivity, requiring 49% and 41% of the patients to be tested, respectively. The combined criterion fPG more than or equal to 5.0 mmol/L and HbA1c more than or equal to 5.7%, provided a similar sensitivity (79%) from testing only 29% of the population.

CONCLUSION: We conclude that patients with an fPG between 5.3 and 6.9 mmol/L or HbA1c more than or equal to 5.8%, alternatively an fPG more than or equal to 5.0 mmol/L combined with HbA1c more than or equal to 5.7% in the early posttransplant period should undergo an OGTT for diagnostic verification of PTDM.