Table 2.

Description of the Global Trigger Tool and Harvard Medical Practice Study

Instrument	Description	Safety outcomes	Conducted by	Scale
Global Trigger Tool34	Two-stage retrospective record review
	Stage 1: Screening records for the presence of triggers and determining the adverse event that caused harm to patients	Triggers (mostly narrow)	Stage 1: Trained nurses or hospital pharmacists (primary reviewers, mostly two reviewers per records) Maximum 20 min per record	Dichotomous: yes/no trigger
	Stage 2: Confirming or dismissing the occurrence and category of the adverse event	Adverse events	Stage 2: Trained physicians (second reviewers, mostly one reviewer)	Dichotomous: yes/no AE Definition of AE: Any unintended physical injury resulting from or contributed to by medical care that requires additional monitoring, treatment or hospitalisation or that results in death
Medical record review based on HMPS3	Two-stage or three-stage retrospective record review
	Stage 1: Screening records using criteria	(Broad) Screening criteria (triggers)	Stage 1: Trained nurses* No time limit	Dichotomous: yes/no trigger
	Stage 2: Detailed review to confirm the presence of adverse events and their preventability	(Preventable) Adverse events	Stage 2: Trained physicians (one or two reviewers per record)	AE determination is based on three criteria: Unintended injury to the patient (dichotomous: yes/no) Resulted in prolongation of hospital stay, temporary or permanent disability or death (dichotomous: yes/no) Caused by healthcare management (six-point scale) Preventability: six-point scale When criteria 1 and 2 are met and the score on criteria 3 is ≥4, then there has been an AE and an AE is preventable when the score on the preventability scale is ≥4
	Stage 3: Discussion or independently supervising review (consensus stage)†		Stage 3: Supervising physician

*With the exception of the study of Brennan et al,³² in which medical records were reviewed by medical-record-room administrators.

†In some studies, a third stage was used.^{3 32 39–42}

AEs, adverse events; HMPS, Harvard Medical Practice Study.