Handling trial participants with missing outcome data when conducting a meta-analysis: a systematic survey of proposed approaches

Table 2 Summary table of proposed general approaches for handling missing participant data for continuous outcomes

	Complete case analysis	Imputations for participants with missing outcome data					Take uncertainty into account	Relation with ITT principle	Approach assesses risk of bias associated with missing data	Testing of the proposed approach
	Complete case analysis	Based on reasons for missingness	Based on mean observed in the same arm	Based on mean observed in the other arm	Based on mean observed in other included trials	Other imputation method	Take uncertainty into account	Relation with ITT principle	Approach assesses risk of bias associated with missing data	Testing of the proposed approach
Ebrahim et al. [9]	✓	✓	✓	✓	✓	–	–	–	✓	✓
Ebrahim et al. [9]	As primary analysis	✓	✓	✓	✓	–	–	–	✓	Applied in 2 meta-analyses of 16 RCTs
Higgins et al. [12]	✓	✓		–		✓	✓	–	–	✓
Higgins et al. [12]	As primary analysis (point of reference)	As primary analysis (preferred)		–		Relative to risk among followed up; best and worst-case scenarios	✓	–	–	Applied in 1 meta-analysis of 20 RCTs

ISSN: 2046-4053