'Risk of bias' assessment of Zhang 2020a
Domain	Assessed outcomes	Authors' judgement	Support for judgement
Representative study group (selection bias)	Not available	High	4 participants only
Outcome detectors blinded to intervention (detection bias)	Adverse events	High	Not blinded, but awareness of intervention can  bias assessment of subjective outcomes
Complete outcome assessment/follow‐up (attrition bias)	Adverse events	Unclear	Clinical course reported, but not whether adverse events occurred
Well‐defined study group (reporting bias)	Not available	Unclear	Study group well described but not intervention
Well‐defined outcome (reporting bias)	Adverse events	High	Not described in detail, unclear whether adverse events occurred
Well‐defined risk estimates (analyses)	Adverse events	Not available	No analyses performed
Important prognostic factors or follow‐up taken adequately into account (confounding)	Not available	High	Not adjusted for confounding factors