A WONG1,2, C MANNIX1,2, J ZHANG1,2, A RANGAN3, G RANGAN1,2
1Centre for Transplant and Renal Research, Westmead Institute for Medical Research, University of Sydney, Westmead, Australia, 2Department of Renal Medicine, Westmead Hospital, Western Sydney Local Health District, Sydney, Westmead, Australia, 3Nutrition and Dietetics, School of Life and Environmental Science, The University of Sydney, , Sydney, Australia
Aim: To test the hypothesis that the Scored Sodium Questionnaire (SSQ) is reliable for detecting HSI in adults with ADPKD.
Background: The restriction of dietary salt (≤100mmol/L) may reduce the growth of kidney cysts in autosomal dominant polycystic kidney disease (ADPKD). The SSQ is a validated tool to screen for high dietary salt intake (HSI) in elderly patients with Stage 3-5 Chronic Kidney Disease but its use in ADPKD is not known.
Methods: Patients with ADPKD (18 to 67 years old; eGFR≥30 mL/min/1.73m²) participating in the PREVENT-ADPKD study self-completed the SSQ at the Screening Visit. HSI was defined as 24-hour urine sodium excretion >100mmol/L. Receiver operating characteristic (ROC) analysis was used to determine the ideal cut-off for SSQ score in ADPKD population.
Results: The majority (78%) of the cohort (n=126; 43% male; 44±12 years old; 24-hour urine sodium 144±56mmol/d mean±SD) were HSI consumers. HSI positively correlated with younger age and male gender but not height-corrected total kidney volume. The SSQ score was higher in HSI (76.4±22.1 vs. 65.3±24.9; P=0.02) but correlation with 24-hour urine sodium was weak (Spearman rho r=0.184, P=0.040). By multivariate analysis, the combination of age, gender and the SSQ score predicted HSI (P<0.001). ROC analysis identified the ideal SSQ cut-off for was 74 to identify HSI (area under the curve, sensitivity and specificity was 0.644, 61% and 75%, respectively).
Conclusion: Consideration of demographic factors (age<40 years old; male gender) together with the SSQ score (>74) may assist in identifying ADPKD patients at risk for HSI who might benefit from formal dietetic consultation. Further refinement of the SSQ scoring system might help improve the performance of this approach in the ADPKD population.
Dr. Annette Wong is a postdoctoral research scientist in renal nutrition. She is interested in polycystic kidney disease and understanding the impact of diet and lifestyle on disease progression.