Credible learning of hydroxychloroquine and dexamethasone effects on COVID-19 mortality outside of randomized trials.

Objectives: To investigate the effectiveness of hydroxychloroquine and dexamethasone on coronavirus disease (COVID-19) mortality using patient data outside of randomized trials.

Design: Phenotypes derived from electronic health records were analyzed using the stability-controlled quasi-experiment (SCQE) to provide a range of possible causal effects of hydroxychloroquine and dexamethasone on COVID-19 mortality.

Setting And Participants: Data from 2,007 COVID-19 positive patients hospitalized at a large university hospital system over the course of 200 days and not enrolled in randomized trials were analyzed using SCQE.

Inference without randomization or ignorability: A stability-controlled quasi-experiment on the prevention of tuberculosis.

The stability-controlled quasi-experiment (SCQE) is an approach to study the effects of nonrandomized, newly adopted treatments. While covariate adjustment techniques rely on a "no unobserved confounding" assumption, SCQE imposes an assumption on the change in the average nontreatment outcome between successive cohorts (the "baseline trend"). We provide inferential tools for SCQE and its first application, examining whether isoniazid preventive therapy (IPT) reduced tuberculosis (TB) incidence among 26 715 HIV patients in Tanzania.