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The recommendation of a low-protein diet for patients suffering from non-dialysis-dependent chronic kidney disease (NDD-CKD) aims to attenuate renal disease progression and improve metabolic control. Adherence to this dietary regimen plays a pivotal role in reaching its renoprotective effect. Two primary methodologies used to estimate protein intake in NDD-CKD patients are Dietary Records (DR) and equations based on urinary urea nitrogen, such as the Maroni´s formula (MF). This study investigates the agreement between these two methods.
During the period between March 2022 and April 2023, both approaches, DR and equation, were applied to 30 NDD-CKD outpatients who attended nephrology consultations. The MF computation relied on biochemical and urinary data obtained from 24 hour urinary urea collection. Concerning the DR method, patients underwent two separate interactions: initially, to receive instructions on conducting the DR, and subsequently to collect the requisite data. Notably, the DR had to be conducted on the same day as the urine collection. The analysis of correlation between these two methods was conducted utilizing the Bland Altman Plot, with previously established acceptable limits of agreement set at ± 5 grams of protein.
The mean difference between the paired datasets was -1.7 units. The calculated limits of agreement were 36.887 (upper) and -40.289 (lower). Given that the statistical limits of agreement significantly surpass the accepted thresholds, it is concluded that the variability observed between the measurements obtained through both methods is too substantial to establish a meaningful correlation. No statistically significant differences were found between sex (p=0.847) or severity of kidney disease (p=0.062), and a difference in results between both methods greater or less than 5 units.
Considering the distinctive strengths and limitations inherent to each method when considered individually, it is recommended to adopt a combined approach during medical-nutritional consultations. Furthermore, it is advisable to institute a regimen of regular and periodic monitoring to comprehensively evaluate both dietary intake and the nutritional status of patients with CKD. This proactive approach not only enhances the understanding of dietary patterns but also ensures that the nutritional needs of CKD patients are consistently addressed, aligning with the overarching objective of improving their health outcomes.