Transplant estimated function : a simple index to evaluate β-cell secretion after islet transplantation

OBJECTIVE: The beta-score is a highly regarded approach to the assessment of transplant functionality. Our aim was to develop an index of β-cell function that hinges on the pillars of the β-score (daily insulin requirement and A1C), has a straightforward physiological interpretation, and does not require the execution of an insulin stimulation test. RESEARCH DESIGN AND METHODS: The new index is denoted transplant estimated function (TEF) and is obtained from the daily insulin requirement and A1C. TEF estimates the amount of insulin secreted daily and can be normalized to the number of transplanted islets, thus permitting evaluation of the cost-effectiveness of the transplant. TEF was compared with the area under the curve of C-peptide [AUC(C-pep)] concentration over 24 h, as well as the acute insulin response to intravenous glucose (AIR(glu)) and to arginine (AIR(arg)). The association between TEF and beta-score was also investigated. RESULTS: The correlation of TEF with 24-h AUC(C-pep) was r = 0.73 (P < 0.005), whereas that for β-score versus 24-h AUC(C-pep) was r = 0.33 (NS). The correlation of TEF with AIR(glu) was r = 0.59 (P < 0.001) and close to that for β-score versus AIR(glu) (r = 0.65, P < 0.001). The correlation of TEF with AIR(arg) was r = 0.33 (P < 0.005) and was similar to that for beta-score versus AIR(arg) (r = 0.34, P < 0.005). TEF and β-score were correlated well (r = 0.69, P < 0.0001) and showed similar time profiles. CONCLUSIONS: TEF estimates daily insulin secretion, it is simpler than the β-score, and its performance against reference indexes of β-cell secretion is in line with that exhibited by β-score. TEF can be normalized to the number of transplanted islets and thereby provides a benchmarking tool to evaluate the cost-effectiveness of the transplant.