The objective of this study is to compare the risk of serious adverse events associated with the use of sodium-glucose cotransporter 2 (SGLT2) inhibitors in comparison with the use of dipeptidyl peptidase-4 (DPP-4) inhibitors among patients with type 2 diabetes. More specifically, the investigators will assess the risk of severe urinary tract infection (urosepsis), diabetic ketoacidosis (DKA) and lower extremity amputation.
A common-protocol approach will be used to conduct retrospective cohort studies using administrative health care data from seven Canadian provinces (Alberta, British Columbia, Manitoba, Nova Scotia, Ontario, Quebec, and Saskatchewan) and the United Kingdom (UK) Clinical Practice Research Datalink (CPRD). Briefly, the Canadian databases include population-level data on physician billing, diagnoses and procedures from hospital discharge abstracts, and dispensations for prescription drugs. The data in Ontario will be restricted to patients aged 65 years old and older. The CPRD is a clinical database that is representative of the UK population and contains the records for patients seen at over 680 general practitioner practices in the UK; these data will be linked to the Hospital Episode Statistics (HES) database, which contains in-hospital diagnosis and procedure data.
In each jurisdiction, the investigators will assemble a source population that includes all patients who received an antidiabetic medication (metformin, sulfonylureas, thiazolidinediones, DPP-4 inhibitors, SGLT2 inhibitors, GLP-1 receptor agonists, alpha-glucosidase inhibitors, meglitinides, insulin, or combinations of these drugs) between January 1, 2006 and June 30, 2018 (or the latest date of data availability at each site). From this source population, a study-specific cohort including all new users of SGLT2 inhibitors or DPP-4 inhibitors between January 1, 2013 and June 30, 2018 (or latest date of data availability at each site) will be created for each safety outcome. Specific exclusion criteria will be applied for each study cohort. Study cohort entry date will be defined by the dispensation date (or prescription for CPRD) of the newly prescribed SGLT2 or DPP-4 inhibitor. Patients will be followed until the occurrence of an event (defined below), death, end of health care coverage, or end of the study period, whichever occurs first.
Exposure will be defined using a time-varying exposure definition in which each person-day of follow-up will be classified into one of the following three mutually-exclusive categories: current use of SGLT2 inhibitors, current use of DPP-4 inhibitors, or other treatment combinations. For all categories, exposed person-time will be defined by the prescription duration plus a 30-day grace period. DPP-4 inhibitors will serve as the reference category as both classes are second- to third-line therapy. The outcome of interests include urosepsis, DKA and lower extremity amputation. In the urosepsis specific-study, Fournier's gangrene will be assessed in descriptive analyses as a secondary outcome.
Statistical analyses will be conducted separately for each study-specific cohort. Site-specific rates and corresponding corresponding 95% confidential intervals (CI) of each safety outcomes will be estimated using the Poisson distribution. Time-dependent Cox proportional hazards models with follow-up time as the underlying time axis will be used to estimate adjusted hazard ratios (HR) and corresponding 95% CI of the association between current use of SGLT2 and DPP-4 inhibitor use and urosepsis, DKA, and lower extremity amputation. As secondary analyses, each safety outcome will be stratified by age (≥70 and \<70 years), sex and SGLT2 molecule. Sensitivity analyses will be performed to assess the robustness of study results and address some of the study limitations. Site-specific results will be combined by random-effects meta-analysis to provide an overall assessment of the risk of serious adverse events in users of SGLT2 inhibitors in comparison to users of DPP-4 inhibitors.
