Development and Validation of a Dietary Screening Tool for High Sodium Consumption in Australian Renal Patients

Abstract

Objective: The study objective was to develop and evaluate the feasibility and validity of a self-administered Scored Sodium Questionnaire (SSQ) for use in the routine clinical care of Australian chronic kidney disease (CKD) patients. Design and Methods: The study took place in community-based outreach clinics using a multidisciplinary model of care. Assessment of sources of dietary sodium intake in the target population used comprehensive diet history interviews (Phase 1) to inform development of a 10-item food frequency questionnaire that was scored and validated using 24-hour urinary sodium and 2 alternative dietary intake methods (Phase 2). Subjects were adults with CKD Stages 3 to 5 (Phase 1 n 5 30; Phase 2 n 5 47). Intervention: On a single day, participants (n 5 47) completed the SSQ, feasibility survey, 24-hour urine collection, and 24-hour food record. A diet history interview was also conducted to confirm sodium intake on the day of data collection reflected habitual intake. Main Outcome Measure: Validity of the SSQ score was confirmed by correlation with 24-hour urine sodium. Validity of a cutpoint on the SSQ score to correctly identify high- versus low-sodium consumers was confirmed by receiver operating characteristic curve analysis: area under the curve, sensitivity, and specificity. Results: Total SSQ score correlated significantly with 24-hour urine sodium (r 5 0.371; P 5 .031). Correlation between 24-hour food record and diet history sodium confirmed consumption on the data collection day reflected habitual intake (r 5 0.701; P # .001). A cutpoint of 65 or greater on the SSQ score was confirmed as valid to identify high-sodium consumers: area under the curve 0.713, sensitivity 61%, and specificity 82%. Conclusion: The SSQ is feasible and valid to assess habitual sodium intake in the Australian CKD population and to identify high high sodium consumers for referral to individualized counseling on a low-sodium diet.