Development and validation of an instrument to assess Brazilians' knowledge, perceptions, and behaviors toward salt and sodium

This study aimed to develop and validate an instrument to assess Brazilian adults' knowledge, perceptions, and behaviors (KPB) toward salt and sodium. Based on a PAHO/WHO questionnaire, a new instrument was developed and evaluated by 11 experts, generating item and scale-level content validity indexes (I-CVI and S-CVI, respectively). Face validity was verified through a focus group with eight participants, followed by an operational test with 36 interviewees. Exploratory factor analysis (EFA) was used to determine the construct validity, and Cronbach's alpha coefficient was calculated to analyze instrument's reliability, using data collected via telephone from a probabilistic sample of 422 adults. The generated solutions were analyzed from theoretical and statistical significance perspectives, which supported the determination of the best model. Remaining items were scored, with higher scores related to healthier practices. A descriptive analysis was performed considering the data from the 422-adult sample. I-CVIs (0.73-1), S-CVIs (0.93; 0.97) and the interviewees' analysis indicated that items are representative and clear, in addition to being suitable for application to the target audience. Tests confirmed sample adequacy to perform the EFA (KMO = 0.82; Bartlett's sphericity test, p < .001). The final validated model, with 16 items, sufficiently explained the variance and presented good reliability (Cronbach's alpha = 0.81; 95% CI 0.79 - 0.84). Women, older individuals, and with higher education had significantly higher scores, regardless of chronic diseases diagnosis (p < .001). This instrument is ready to be applied and easily reproduced, contributing to the assessment of KPB toward salt and sodium in Brazil.