Psychometric testing of an instrument designed to measure nutritional perceptions of hypertensive patients

Measurement tools designed to ensure the achievements of studies' objectives must be evaluated. Based on the health promotion model (HPM), the present study was conducted to assess the validity and reliability of the designed questionnaire of hypertensive patients' nutritional perceptions.

In a cross-sectional study, the mentioned questionnaire was assessed based on opinions of 11 experienced faculty members and 671 hypertensive patients in rural areas in the year 2013. To evaluate the reliability, internal consistency (Cronbach's alpha) was calculated. Concerning the validity of the questionnaire, its content and construct validity were examined. Data analysis was performed using Statistical Package for the Social Sciences version 18 (SPSS Inc., Chicago, IL, USA).

Spearman-Brown and Cronbach's alpha coefficients results were acceptable in all constructs indicating a satisfactory reliability of the questionnaire. Questionnaire's questions were highly correlated with the total score signifying the internal consistency of the questions; therefore, all questions had a similar effect on the total score and the removal of each did no increase the alpha significantly (all questions had acceptable reliability). Factor analyses showed that all questions had acceptable factor loading and suitable validity. Moreover, the entire constructs of the questionnaire were approved by experts with high validity coefficient of 0.9.

The designed questionnaire for assessment of the HPM constructs regarding hypertensive patients' nutritional issues had appropriate psychometric characteristics. Reliability and validity of the questionnaire were also satisfactory and its overall structure was approved.