Measurement invariance across chronic conditions: a systematic review and an empirical investigation of the Health Education Impact Questionnaire (heiQ™)

Table 1 Search terms, filter terms and inclusion/exclusion criteria

Search terms	“Measurement invariance”, “factorial invariance”, “measurement equivalence”, “differential item functioning”, “item bias”
Filter terms	Chronic, diagn, patient, rehab, cancer, arthrit, inflam, diab, rheum, orthop, respir, asthm, copd, health, quality of life, self management, self-management, empowerment, diseas, depress*, anxiety, trauma, injury
Inclusion criteria	(a) empirical study of MI among different chronic conditions
	(b) generic questionnaire
	(c) adults
	(d) English or German language
Exclusion criteria	(a) only MI between factor correlations were studied, although scales were not combined to a total score;
Exclusion criteria	(b) instruments measure disease-related constructs such as disease-specific quality of life;
	(c) only specific subgroups of a chronic conditions were studied (e.g., patients with right- vs. left-hemispheric lesions).

ISSN: 1477-7525