#842 Validation of the excessive salt intake screening questionnaire in CKD patients
Authors: Iida Hidekazu , Miho Ken , Takai Miki , Abe Kouki , Yoshimura Kensuke , Yamagata Ryohei , Nishiba Yosuke , Watanabe Michihisa , Inoue Mariko 
Published: May 2024

Abstract

Background and Aims
Excessive salt intake is implicated in the progression of hypertension, chronic kidney disease (CKD), diabetic nephropathy, cardiovascular diseases, cerebrovascular diseases, and increased mortality. In Japan, average salt consumption surpasses the levels recommended by national guidelines and the WHO. However, individuals seldom have the chance to gauge their salt intake accurately. This study aimed to validate a screening tool initially developed by Sasaki et al. to identify individuals with excessive salt intake using health check-up data from Asahi City, Chiba Prefecture, Japan.

Method
This study was conducted as a part of the Cities Changing Diabetes (CCD). CCD is Novo Nordisk's commitment to drive action against type 2 diabetes and obesity in cities globally. It is a partnership program to accelerate the prevention of diabetes and obesity by addressing the systemic change in urban environments. Participants of this study were drawn from specific health examinations in Asahi City. Consent was obtained, and dialysis patients were excluded. Spot urine samples were analyzed for sodium and creatinine to estimate daily salt intake via Tanaka's formula. The screening tool incorporated risk factors such as age, gender, Body Mass Index (obesity), hypertension (use of antihypertensive drugs), frequency of soup intake, saltiness of home-cooked meals compared to restaurants, efforts to reduce salt intake, and frequency of dining out. The primary outcome was excessive salt intake, defined as an intake exceeding one standard deviation above the mean. Discrimination was assessed using the Area Under the Curve (AUC), while calibration was evaluated with a calibration plot and the Hosmer-Lemeshow test.

Results
Of the 1532 CKD participants, the mean age was 76.3 years, with males comprising 46%. The average daily salt intake was 9.3 g (SD: 2.39), and the estimated Glomerular Filtration Rate (GFR) was 50.6 ml/min/1.73 m² (SD: 14.5). The distribution of CKD stages included 1198 stage 3a, 285 stage 3b, 43 stage 4, and 5 stage 5 patients. The AUC of screening tool was 0.65 (95% CI: 0.61 to 0.69), and its calibration slope (with an intercept) was 0.98 (95% CI: 0.72 to 1.25). The Hosmer-Lemeshow test yielded a p-value of 0.626.

Conclusion
The predictive capability of the existing model for excessive salt intake was limited in the CKD population, which may suggest a need for a screening method distinct from that used in the general population. Factors such as changes in sodium excretion due to reduced renal function and the effects of diuretics should also be considered when interpreting these results. Integrating this questionnaire into routine health check-ups could enhance dietary monitoring and intervention, potentially attenuating the progression of CKD and its associated complications. There remains scope for further refinement of the tool's accuracy by incorporating additional predictors.