Determination of concordance between Bio-Impedance analysis and a clinical score in fluid status assessment of Patients on Maintenance Haemodialysis

Abstract

Background: The burden of chronic kidney disease (CKD) is rising rapidly globally. Fluid overload (FO), an independent predictor of mortality in CKD, must be quantified accurately to enable maintenance of normohydration. Clinical assessment is widely used to determine FO but its individual elements may not be precise and could result in underestimation of FO. Conversely, bio-impedance analysis (BIA) has been shown to be accurate and reproducible in determining fluid status of CKD patients on haemodialysis (HD). However, it is unclear which of the two methods is more sensitive in assessing volume status in our population. Objective: To assess the hydration status of maintenance HD patients using BIA and assess the level of agreement between BIA and a clinical score (CS) in fluid status assessment. Methodology: This was a single centre hospital based cross-sectional analytic study that recruited a sample of 80 CKD patients at the renal unit of Kenyatta National Hospital. Included patients were 18 years of age or older, on maintenance HD, without a pacemaker, metallic implant or bilateral limb amputation. Data on the patients’ clinical history, physical examination and chest radiography findings were filled into a predesigned questionnaire. Using the same questionnaire, data on determinants of fluid overload was collected. Bio-impedance analysis for fluid status was then performed on each of the study participants. Bio-impedance analysis was used as the reference to which the CS was compared. The sensitivity and specificity of the CS was computed and used to plot a receiver operating characteristic (ROC) curve that was used to ascertain the ideal cut-off point for the CS. McNemar’s chi-square was used to check for association between fluid overload status by BIA and CS. Logistic regression was used to analyse the factors associated with FO. Results: A high proportion of patients on maintenance HD have FO (88.75%) with mean excess extracellular volume being 3.02 L + 1.79 L. There was a statistically significant difference in the proportion of patients diagnosed to have FO using BIA and the CS (p-value <0.0001, 95% CI 0.1758 – 0.4242). The best cut-off point identified for the CS was four with values >4 indicating FO and values < 4 indicating no FO. At this cut-off point, the CS had a sensitivity of 63% and a specificity of 78%. None of the factors assessed had a statistically significant association with FO on multivariable logistic regression analysis. Conclusion: In this population, BIA was able to diagnose FO more frequently than the CS. Further studies need to be done to determine the consistency of these findings.