Fluid Intake Appraisal Inventory: development and psychometric evaluation of a situation-specific measure for haemodialysis patients' self-efficacy to low fluid intake

OBJECTIVE: Self-efficacy is an important determinant of health behaviour and reflects a person's belief about their capability to complete a given task. The relationship between self-efficacy and fluid adherence has been investigated, although limited attention has been given to measurement issues. The purpose of this study was to develop a measure of situation-specific self-efficacy for constructive fluid intake behaviour in haemodialysis patients, the Fluid Intake Appraisal Inventory (FIAI). METHODS: Items were generated from an analysis of empirical studies available in the literature and exposed to an interpretability critique before haemodialysis patients confirmed sufficiency of each item. In a multi-centre study, data from 144 haemodialysis patients were collected regarding general self-efficacy, situation-specific self-efficacy, and estimated fluid consumption. Internal consistency, criterion-related validity, and structural validity were tested. RESULTS: The FIAI was found to have high internal consistency (Cronbach alpha 0.96) and the theoretical assumptions for criterion-related validity and known-group validity were supported. Structural validity was not confirmed, however, because the theoretically hypothesized four-factor model was not the prime structure. CONCLUSION: The FIAI was revealed to have satisfactory psychometric properties. The scale may be used in research or in clinical settings to study the mediating effects of self-efficacy or to modify haemodialysis patients' fluid-intake behaviour. Although this first validity study is promising, further validation focusing on reliability and cultural validity is needed.