Excellence of suito index for assessing clinical outcome of islet transplantation

Abstract

Background: Monitoring functional islet mass after transplantation is critical to follow patients. Previously we demonstrated that the average secretory unit of islet transplant objects (SUITO) index within 1 month was an excellent predictor of insulin-free status or reduction in insulin dose. In this study, we analyzed the usefulness of daily SUITO index to assess clinical outcomes.

Methods: Five patients underwent islet transplantation, including 3 who received 2 transplantations and 2 who received a single graft. All 5 patients achieved insulin-free status with 3 remaining insulin free at the time of evaluation. We analyzed the daily relative insulin dose and SUITO index. The daily relative insulin dose was calculated as the total daily insulin dose/average pretransplant insulin dose. The SUITO index was calculated as [fasting C-peptide (ng/mL)]/[fasting blood glucose (mg/mL) - 63] x 1,500. The data analyzed based on time after islet transplantation were categorized as within or after 1 month.

Results: Within 1 month after islet transplantation, there was no correlation between the daily relative insulin dose and the daily SUITO index (P = .068; R = -0.33). After 1 month, the daily relative insulin dose and the daily SUITO index were strongly correlated (P < .0001; R = -0.70). When the cutoff value of the SUITO index was decided at 26 for insulin-free status, the positive predictive value was 84.1% and negative predictive value 89.4%.

Conclusion: SUITO index was an excellent index to assess clinical outcomes beyond 1 month after islet transplantation.