Sodium/Glucose Cotransporter 2 Inhibitors and the Risk of Diabetic Ketoacidosis: An Example of Complementary Evidence for Rare Adverse Events.

Evidence from observational studies may be considered complementary to that of randomized controlled trials (RCTs), particularly when assessing rare outcomes of drug therapies. Sodium/glucose cotransporter 2 (SGLT-2) inhibitors are a novel class of antidiabetic agents that have been linked to an increased risk of diabetic ketoacidosis (DKA). We conducted a systematic review and separately meta-analyzed data from RCTs (n = 18; 2013-2019) and cohort studies (n = 7; 2017-2020) to assess the consistency of the magnitude of association between SGLT-2 inhibitors and DKA risk. We illustrate the strengths and weaknesses of the 2 designs. Results from RCTs and observational studies consistently showed almost a doubling in the risk of DKA among patients using an SGLT-2 inhibitor as compared with placebo or an active comparator. In a random-effects model, the pooled relative risk was 2.08 (95% confidence interval (CI): 1.28, 3.40) from placebo-controlled RCTs and 0.82 (95% CI: 0.25, 2.68) from active-comparator RCTs. The pooled adjusted hazard ratio from observational studies was 1.74 (95% CI: 1.28, 2.38). Notably, the 2 designs complement each other in several domains, including external and internal validity and power. This demonstrates a need for more comprehensive evidence when assessing rare adverse events for both sources.