Table 1.

Inclusion and exclusion criteria for study selection based on PICOS

Selection criteria	Inclusion criteria	Exclusion criteria
Population	LMICs	Non-LMICs
Intervention	Isolated demand-side user charge changes attributed to financing policy or health insurance scheme for health services, including increased, decreased, introduction and abolition of user charges. The study could either mention direction or magnitude changes in amount or proportion of user charges	Examined complex intervention: both of demand-side and supply-side intervention Examined concurrent policy changes Only examined the impact of health insurance without explicitly mentioning changes in user charges
Comparator	Individuals or communities in LMICs that were not exposed to user charge changes during the period of study	None
Outcome	All types of health outcomes (eg, general health status, mortality, non-communicable disease, infectious disease, nutritional and anthropometric measurements)	Only assessed health service use
Study design	Quasi-experimental study design: difference-in-differences, propensity score matching, instrumental variable, regression discontinuity, interrupted time series and any combination of these designs Randomised control trial, cluster-randomised control trial	Cross-sectional study, simple before–after comparison, qualitative study, cost–benefit/cost-effectiveness analysis, systematic review, meta-analysis, commentary

LMIC, low-income to middle-income country.