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Evaluation of 2 methods for sodium intake assessment in cardiac patients with and without heart failure: the confounding effect of loop diuretics

Arcand, JoAnne, Floras, John S., Azevedo, Eduardo, Mak, Susanna, Newton, Gary E., Allard, Johane P.
The American journal of clinical nutrition 2011 v.93 no.3 pp. 535-541
cardiovascular diseases, correlation, diuretics, food intake, food records, heart, patients, sodium, urine
BACKGROUND: Twenty-four-hour urine collections are considered the optimal method for sodium intake assessment. Whether a diagnosis of heart failure (HF) or the use of loop diuretic (LD) therapy for HF compromises the validity of 24-h urine collections as a surrogate marker for sodium intake is unknown. OBJECTIVE: The objective was to determine the strength of association between 24-h urine collections and food records for sodium intake assessment in non-HF cardiac patients and in HF patients stratified by LD usage. DESIGN: Food records and 24-h urine collections were simultaneously completed for 2 consecutive days. Correlation coefficients and the Bland-Altman method of agreement described the relation between the techniques. RESULTS: Non-HF cardiac patients (n = 96; mean ± SD age: 65 ± 11 y), HF patients who were not taking an LD (n = 47; 62 ± 11 y), and HF patients who were taking an LD (n = 62; age: 60 ± 12 y) were included. Correlation coefficients for sodium intake between food records and urine collections were r = 0.624 (P < 0.001) for non-HF cardiac patients and r = 0.678 (P < 0.001) for HF patients who were not taking an LD. However, no significant association (r = 0.132, P = 0.312) was observed for HF patients who were taking LDs. The 95% limits of agreement between the non-HF cardiac patients and the HF patients who were not taking LDs were similar but were [almost equal to]50% wider for HF patients who were taking LDs. CONCLUSIONS: For the assessment of sodium intake, food records agree well with 24-h urine collections in non-HF patients with cardiovascular disease and in HF patients who are not receiving LD but not for HF patients who are taking LDs. Therefore, food records may provide a better estimate of sodium intake in HF patients who are receiving LD therapy.