Intra- and extra-individual biological variability of total calcium, urea, and creatinine in pre-dialysis and post-dialysis adult patients with chronic renal failure.

Abstract

Introduction: The intra- and inter-individual variability of calcium, urea, and creatinine in hemodialysis patients depends on their nutritional status and the removal produced by the treatment. The objective of the present study was to determine the variability over a 10-month observation period in a group of patients in a hemodialysis program.

Methods: This longitudinal study was conducted with adult patients with stage 5-d chronic kidney disease from the Clinef-Norte dialysis center in Quito, Ecuador. The variables were age, sex, urea, creatinine, and total calcium before and after dialysis. The sample was probabilistic, consisting of 120 cases. The individual biological variation (CVI), the inter-individual biological variation (CVG), the change reference value, and the relative variation coefficient (CVR) were calculated.

Results: 165 cases, 60.5 ± 15.2 years old, were analyzed. The CVI of urea was 0.36%, and CVG of 0.87% pre-dialysis, 24.3%, and 28.94% post-dialysis. Creatinine CVI was 10.8%, CVG 24.23% pre-dialysis, post-dialysis CVI 12.9%, and CVG 36.36%. The CVI of Calcium was not calculable; the CVG was 7.31%.

Conclusions: The CVI of pre-dialysis urea indicated a regular protein intake, a finding with significant implications for patient care. The CVI of post-dialysis urea was variable and is related to differences in the prescription of the extracorporeal flow of hemodialysis, highlighting the need for personalized treatment. The CVI of serum creatinine has implications for constant loss of muscle mass in the study time, a practical consideration for patient management. Calcium GVC was associated with an increase in calcaemia in the first four months and a continuous fall after this period, probably associated with a decrease in the intake of calcium products after the 4th month of dialysis treatment, a finding that can guide dietary recommendations.