Table 1. Criteria for study bias assessment.

Criteria	Description
Infection diagnostics	Is a diagnostic assay clearly mentioned? Is there any form of quality control in the diagnostic process (e.g., a senior technician doing spot-checks)?
Exposure assessment	Was exposure assessment (e.g., access to clean water, washing hands) ascertained via a self-reported survey response (unreliable) or observed directly by investigators (more reliable)? Is there any attempt to gauge proper use of water, hygiene, or some form of “quality control” for the exposures?
Confounding assessment	Are only crude estimates computed? Has matching and/or multiple logistic regression been undertaken to control for important potential confounders?
Response rate	Is the response rate (or loss-to-follow-up) similar for infected versus non-infected individuals?
Selective reporting	Is there evidence of selective reporting within an article (e.g., outlining certain variables of interest in the methods but not providing any data on them in the results)?