Islet Transplantation Versus Standard of Care for Type 1 Diabetes Complicated by Severe Hypoglycemia From the Collaborative Islet Transplant Registry and the T1D Exchange Registry

OBJECTIVE Islet transplantation was recently approved by the U.S. Food and Drug Administration for adults with type 1 diabetes complicated by recurrent severe hypoglycemia events (SHEs). We sought to understand the long-term benefit for glycemic control and risk of immunosuppression to kidney function associated with islet transplantation compared with ongoing standard of care. RESEARCH DESIGN AND METHODS We performed a case-control analysis of prospectively collected data from patients in the Collaborative Islet Transplant Registry (CITR) with at least one SHE in the year (2000–2014) before transplantation (case subjects) and compared them with data from patients in the T1D Exchange (T1DX) Registry with at least one SHE in the year (2010–2012) before enrollment (control subjects), with both cohorts observed over 5 years. SHEs were restricted to those resulting in seizure or loss of consciousness. RESULTS Case subjects from CITR (n = 71) compared with control subjects from T1DX (n =213) more often achieved the primary outcome of HbA_1c <7.0% and absence of an SHE (71–80% vs. 21–33% over 5 years; P < 0.001) and the outcome of HbA_1c #6.5% and absence of an SHE (60–75% vs. 10–20%; P < 0.001) while requiring significantly less insulin (majority in CITR were insulin independent). Kidney function, measured by estimated glomerular filtration rate, declined from baseline to a greater extent in CITR than in T1DX (28.8 to 220 vs. 21.3 to 26.5 mL. min²¹. 1.73 m²² over 5 years; P < 0.001). CONCLUSIONS Islet transplantation for adults with type 1 diabetes complicated by SHEs results in near-normal glycemic control in the absence of SHEs more often than observed with standard of care, but at the cost of greater reduction in kidney function.