Critical appraisal of multidrug therapy in the ambulatory management of patients with COVID-19 and hypoxemia Part II: Causal inference using the Bradford Hill criteria

Abstract

We continue the critical appraisal of three published case series of 119 COVID-19 patients with hypoxemia, treated in the United States, Zimbabwe, and Nigeria with similar ivermectin-based multidrug treatments, to assess the available evidence supporting a causal relationship between treatment and reduction in hospitalizations and mortality. A narrative review was conducted to assess the Bradford Hill criteria for a causal association. We used a previously proposed refinement of the Bradford Hill criteria that reorganized them into three categories of direct, mechanistic, and parallel evidence. The efficacy of the two most aggressive ivermectin-based multidrug protocols is supported by the Bradford Hill criteria for temporality, strength of association, biological gradient, biological plausibility, coherence, consistency, and analogy. The causal relation between the treatment of hypoxemic COVID-19 patients using these protocols and the reduction in hospitalizations and mortality is supported as an inference to the best explanation.