Demonstration of psychometric soundness of the Dietary Sodium Restriction Questionnaire in patients with heart failure.
PURPOSE
Recommendation of a low-sodium diet is the most common nonpharmacologic intervention used in patients with heart failure (HF). However, nonadherence to this recommendation is extremely high. There are no instruments available for the specific measurement of patients' perceptions of their barriers to, and attitudes toward, following a low-sodium diet. The purpose of this study was to evaluate the psychometric properties of a new instrument, the Dietary Sodium Restriction Questionnaire (DSRQ). Based on the Theory of Planned Behavior (TPB), the DSRQ assesses adherence through the use of 3 subscales. Each subscale represents a construct of the TPB: attitude, subjective norm, and perceived behavioral control.


METHODS
The sample consisted of 174 patients with HF (age 62.4 +/- 13.5 years, 56.1% were male, 83.8% were white, and 86.9% had New York Heart Association class II/III). Factorial validity was tested using principal component analysis. Reliability was tested using Cronbach's alpha to assess the internal consistency of the 3 subscales. Reliability was further evaluated with item-total correlations and inter-item correlations.


RESULTS
Principal component analysis of the DSRQ resulted in the extraction of 3 factors, each factor corresponding to a construct of the TPB. The 3-factor solution explained a total of 54.2% of the variance, with Attitude contributing 23.4%, Perceived Behavioral Control contributing 18.1%, and Subjective Norm contributing 12.7%. The Cronbach's coefficient alpha for each subscale was Attitude .88, Subjective Norm .62, and Perceived Behavioral Control .76.


CONCLUSIONS
The DSRQ is a valid and reliable tool for measuring patients' attitudes, beliefs, and barriers related to following a low-sodium diet in adult, white patients with New York Heart Association class II/III HF.