Clinical use of fructosamine in islet transplantation.

Many islet transplant recipients have medical conditions that could interfere with the accuracy of HbA1c measurements (e.g., anemia/dapsone use). Fructosamine is less prone to have clinical interferences and reflects glucose control in a shorter period of time than HbA1c. This study aimed to validate fructosamine use in islet transplant subjects and to evaluate its effectiveness as a predictor for islet graft dysfunction. Thirty-three islet transplant recipients who had concomitant fructosamine and HbA1c data available were retrospectively analyzed. HbA1c, fructosamine, mean capillary blood glucose, and islet graft function (fasting C-peptide/glucose ratio) were assessed. There was a significant and positive association between fructosamine and HbA1c (p < 0.0001). Both variables were also positively associated with mean overall and fasting capillary glucose. Neither fructosamine nor HbA1c was shown by ROC analysis to significantly discriminate between periods with and without subsequent graft dysfunction. HbA1c >6% was predictive of this outcome 1 month in advance (OR 2.95, p = 0.003). However, although significantly associated with graft dysfunction, use of this cutoff as a predictor of dysfunction has poor sensitivity (50%) and specificity (77.6%). Fructosamine above the normal range (>270 mumol/L Quest Diagnostics) was also predictive of ensuing dysfunction (OR 2.47, p = 0.03); however, it had similarly poor sensitivity (62%) and specificity (64%). Fructosamine can be used as an alternative to HbA1c for glycemic assessment in islet transplant recipients in situations with HbA1c assay interference. Neither HbA1c nor fructosamine are good predictors of islet graft dysfunction.