β-Score

Abstract

OBJECTIVE—Success after islet transplantation can be defined in terms of insulin independence, C-peptide secretion, or glycemic control. These measures are interdependent and all need to be considered in evaluating β-cell function after islet transplantation. For the current study, a composite β-score was developed that provides an integrated measure of β-cell function success after islet transplantation.

RESEARCH DESIGN AND METHODS—The proposed scoring system gave 2 points each for normal fasting glucose, HbA_1c, stimulated C-peptide, and absence of insulin or oral hypoglycemic agent use. No points were awarded if the fasting glucose was in the diabetic range, the HbA_1c was >6.9%, C-peptide secretion was absent on stimulation, or daily insulin use was in excess of 0.24 units/kg. One point was given for intermediate values. The score ranged from 0 to 8 and was correlated with the glucose value 90 min after a standard mixed meal challenge (n = 218) in 57 subjects before and after islet transplantation. The score was also used to follow subjects for up to 5 years after islet transplantation.

RESULTS—The β-score correlated well with the plasma glucose level 90 min after a mixed meal challenge (r = −0.849, P < 0.001). On follow-up, the β-score rose after the first transplant and was maintained up to 5 years, demonstrating continuing function of the transplanted β-cells.

CONCLUSIONS—The β-score provides a simple clinical scoring system that encompasses glycemic control, diabetes therapy, and endogenous insulin secretion that correlates well with physiological measures of β-cell function. On this basis, it is suitable as an overall measure of β-cell transplant function. The β-score gives an integrated measure of β-cell function as a continuum that may be more useful than simply assessing the presence or absence of insulin independence.