Estimated dietary sodium intake in haemodialysis patients using food frequency questionnaires

In clinical practice, dietary sodium assessment requires reliable and rapid screening tools. We wished to evaluate the usefulness of food frequency questionnaires (FFQ) in estimating dietary sodium intakes in haemodialysis patients.

We used the Derby Salt Questionnaire (DSQ), and Scored Sodium Questionnaire (SSQ) to estimate sodium intake. Body composition was determined by bioimpedance.

In total, 139 haemodialysis patients (95 men) completed the FFQs, with mean ± standard deviation age 67 ± 15 years. The mean FFQ scores were DSQ 3.5 ± 2.0 and SSQ 68.4 ± 24.5. Men had higher estimated dietary sodium intakes [DSQ median (range) 3.6 (0.6-10.1) versus female 2.2 (0.5-9.1), P = 0.007)]. Younger patients and those aged >75 years had the higher SSQ dietary sodium scores; 70.7 ± 27.8 and 76.8 ± 24.6 versus those aged 55-75 years, 61.8 ± 22.3, P = 0.04. Patients with greater estimated sodium intake had higher extracellular water (ECW) to intracellular water (ICW) ratios pre-dialysis [75.1 ±12.5 versus 67.7 ± 4.8, P < 0.001] and ECW excess pre-dialysis [1.8 (1.5-2.6) versus 1.3 (0.8-2.0) L, P < 0.05]. Mean arterial pressure (MAP) and inter-dialytic weight gains did not differ; however, the fall in MAP during dialysis was lower in the higher estimated dietary sodium group (0.9 ± 13.7% versus 6.5 ± 14.1%, P = 0.04).

Both questionnaires were acceptable to patients and identified higher estimated dietary sodium intake for men, those with greater ECW and, somewhat surprisingly, we found that older patients had a greater dietary sodium intake than expected.