OBJECTIVES: Developing a control group of a clinical trial using real world data (RWD) is desirable and ethically sound despite challenges pertaining to internal validity. To examine the internal validity, we reproduced the control group in a Randomized Controlled Trial (RCT) using Electric Health Record (EHR) and evaluated the difference between the outcome of the original trial and that of the reproduced analysis.

METHODS: We selected an RCT, REMDACTA trial, that was performed to evaluated the efficacy of tocilizumab plus remdesivir against placebo plus remdesivir in patients with severe COVID-19 pneumonia and reproduced its control group (patients with severe COVID-19 pneumonia taking only remdesivir), using Japanese EHR data, Millennial Medical Record provided by Life Data Initiative. Target patients for the main analysis were those having U07.1 (COVID-19) of the ICD-10 code, or COVID-19 pneumonia of the diagnosed code. Patients having only COVID-19 pneumonia of the diagnosed code were included for sub analysis. Among these, patients undergoing image inspection, oxygen administration, and not taking any medicines for pneumonia before the first remdesivir prescription, were evaluated for an outcome. Median time of length of stay was compared.

RESULTS: Target patients were 678, including 667 and 110 patients having only U07.1 (COVID-19) of ICD-10 code and only COVID-19 pneumonia of diagnosed code, respectively. However, only 57 and 14 patients matched the eligibility criteria for the main and sub analyses, respectively. The reduction in the number of patients is attributed to the criteria of image inspection and oxygen administration. Median time of lengths of stay in the reproduced group were 13 and 11 days in the main and sub analyses, respectively [11.0–16.0, 95% CI of median time, in REMDACTA].

CONCLUSIONS: We successfully reproduced the median time of the control group by EHR data.