Association between the secretory unit of islet transplant objects index and satisfaction with insulin therapy among insulin-dependent islet recipients

Introduction: When patients do not become insulin independent after islet cell transplantation (ICT), another aim is to eliminate severe hypoglycemia. Previously we reported that a secretory unit of islet transplant objects (SUITO) index score >10 was associated with a reduction of severe hypoglycemia. In this study, we assessed patients' satisfaction with their insulin therapy based on the SUITO index. Methods: The study involved 11 islet recipients with type 1 diabetes who underwent ICT but still used insulin. From those patients, 41 Insulin Therapy Satisfaction Questionnaires (ITSQ) were collected. The SUITO index (fasting C-peptide [ng/mL] × 1500/blood glucose [mg/dL] - 63) was calculated at the same outpatient visits that the survey was administered. ITSQ scores were summarized using subscales and compared among 3 groups: the pre-ICT group, the low-SUITO group (SUITO index score <10 post-ICT), and the high-SUITO group (SUITO index score <10). Higher survey scores indicated better satisfaction. Results: Significant trend relationships across the 3 groups were observed in the ITSQ total score (P =.02 with Jonckheere-Terpstra test) and subscale scores of glycemic control (P <.001), hypoglycemic control (P =.01), and inconvenience of regimen (P =.004). The pairwise comparisons between the 3 groups found significant differences: high SUITO versus both pre-ICT and low SUITO for the total ITSQ score (P =.03 and.005, respectively) and glycemic control score (P =.008 and.001, respectively), and high SUITO versus low SUITO for hypoglycemic control score (P =.04) and inconvenience of regimen score (P =.008). Conclusion: Islet recipients with a SUITO index <10 experienced higher satisfaction with insulin injection therapy compared with the pre-ICT group, even though they were insulin dependent. A SUITO index <10 is a reasonable benchmark for successful ICT.