Subjective global assessment of nutrition, dialysis quality, and the theory of the scientific method in Nephrology practice

Abstract

In an era of evidence‐based medicine and dialysis performance measures, there is strong motivation to find specific, objective, quantifiable, and reproducible parameters to characterize the clinical condition of chronic kidney disease patients and to present population‐wide statistics that may describe quality of care in dialysis centers. Yet, in the last three decades, several studies demonstrated that while parameters including Kt/V urea, serum phosphorus, parathyroid hormone, serum cholesterol fulfill all these criteria, efforts to optimize these lab parameters failed to improve survival on dialysis. However, subjective assessments of nutrition including subjective global assessment and malnutrition–inflammation score, while not ideally suited for statistical analysis and not optimal from the point of view of scientific methodology due to their general, semi‐quantifiable, subjective nature have, nevertheless, proved themselves as some of the strongest predictors of clinical outcomes in the dialysis population. Where does this paradox leave us? We propose that a deeper understanding of relevance of these variables in the dialysis population may improve appreciation of the clinical situation of individual patients and may result in a paradigm shift from dialysis adequacy to quality dialysis.

Acute effects of dietary phosphorus intake on markers of mineral metabolism in hemodialysis patients: post hoc analysis of a randomized crossover trial

“…Such diet-induced changes to markers of mineral metabolism may not be completely detected by the monthly surveillance of laboratory-based measures, which is the current clinical practice of dialysis. As stated in the recent review by Tibor Fülöp and his colleagues [ 20 ], nephrologists have been largely relied on objective laboratory measures that are performed on a monthly basis, and these laboratory measures, such as pre-dialysis serum phosphorus and calcium, provide a snapshot view that may not adequately capture the potentially large daily fluctuations in dietary habits. Using serum concentrations of clinical mineral parameters assumes a chronic steady state, but it is hardly true in the dialysis population because these laboratory parameters are both largely and rapidly dependent on variations in daily diet and hemodynamic instabilities during dialysis procedure.…”

“…Using serum concentrations of clinical mineral parameters assumes a chronic steady state, but it is hardly true in the dialysis population because these laboratory parameters are both largely and rapidly dependent on variations in daily diet and hemodynamic instabilities during dialysis procedure. Tibor Fülöp and his colleagues [ 20 ] also pointed out that assessment of the individual patient’s clinical status based on snapshots of laboratory values are often misinterpreted and occasionally of questionable relevance. Thus, monthly snapshots of mineral parameters may not adequately characterize fluctuations in dietary intake, and cautions should be taken when interpreting these results.…”

“…Based on these observations, we hypothesized that elevated dietary phosphorus intake acutely and negatively affects markers of mineral metabolism. For clinical application, there is concerned that day-to-day variations in nutritional intake may not be captured by current dialysis practice, which adopted monthly assessment of laboratory measures, and these snapshots of laboratory values are potentially misinterpreted and occasionally of questionable relevance [ 20 ]. In order to examine the relationship between dietary phosphorus intake and serum mineral parameters, a post hoc analysis was conducted on existing data from our previous study to evaluate the short-term effects of dietary phosphorus intake on markers of mineral metabolism in patients with ESKD undergoing hemodialysis.…”

Estimated Glomerular Filtration Rate in Chronic Kidney Disease: A Critical Review of Estimate-Based Predictions of Individual Outcomes in Kidney Disease

“…There is no doubt that an association exists between malnutrition and advanced CKD as assessed by eGFR [85]; nevertheless, a considerable inter-individual variety may be present at any given eGFR including even in CKD-5D patients depending on age, comorbidity, presence of metabolic acidosis, anemia, chronic inflammation, hypervolemia, intestinal dysbiosis, and other factors [86]. Metabolic acidosis that may or may not correlate with eGFR in a particular individual has been independently correlated with malnutrition [87], catabolism [88], as well as cardiovascular [89] and renal outcomes including a faster progression of CKD [90].…”

“…The argument has been made to consider clinical and nutritional assessments as an important factor determining the timing of renal replacement therapy initiation [95]. It is also clear that a subjective assessment of nutrition with or without an assessment of frailty is one of the most important predictors of clinical outcomes on both hemodialysis and peritoneal dialysis and are superior to assessments of dialysis clearance in this regard [86]. While we may regard eGFR or eKT/v urea as our predominant tool for the assessment of the risk for clinical outcome in CKD especially at the population level, we must be cognizant of the fact that even though these parameters are easy to obtain, easy to document, objective, quantifiable, reproducible, and might seem easy to interpret, they nevertheless do not represent a comprehensive tool in assessing risk and may not correlate well with other independent predictors of outcome, including the subjective global assessment of nutrition [96] in a given individual.…”