## 2 Monitoring of Nutritional Status in CKD Patients: Affected Parameters  
Deterioration into a state of malnutrition in CKD and HD patients [24] up until onset of PEW [25], is linked to a series of key parameters, as illustrated in Table 1. Indeed, several interfering factors should be taken into consideration in the diagnosis of malnutrition and/or PEW: When calculating BMI, ethnic origin should be taken into account and when determining hyperhydration status, post-hemodialysis dry weight should be considered. Anthropometric measurements should be taken by a skilled nutritionist, and plicometry to estimate fat mass [26] and bioimpedance analysis [27; 28] should be performed preferably by the same nutritionist. These biochemistry parameters are not pertinent in patients with significant proteinuria (over 3 g/day) or nephrotic syndrome, liver disease, or cholesterol-lowering drug consumption. Creatinine is strongly influenced by protein intake, particularly the last meal (lunch or dinner) consumed prior to HD, and by muscle mass (sedentary or active) and age. The most effective methods based on assessing protein intake based on protein catabolic rate (PCR) should be applied, particularly as dietary assessment or recall may yield ambiguous or inaccurate findings [29]. Whilst estimation of urea nitrogen appearance (UNA) remains a valid parameter [30] in the assessment of CKD patients, when using a urea kinetic model equilibrated normalized protein catabolic rate (eqPCR) in HD patients should only be estimated in the presence of steady-state metabolism. Determination of eqPCR should be avoided if the patient is suffering from an inflammatory and/or hypercatabolic condition [31].  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Malnutrition** & **PEW** \\ \hline
**first alternative** & **at least three out of the four listed grouping and at least one test in each one** \\ \hline BMI \(<\) 18.5 kg/m\({}^{2}\) & BMI \(<\) 23 kg/m\({}^{2}\); Unintentional weight loss \(>\) 10\% over 6 months or \(>\) 5\% over the last three months; total body fat \(<\) 10\% \\ \hline
**second alternative** & \\ \hline Unintentional weight loss \(>\) 10\% (indefinite time) or \(>\) 5\% over the last three months & serum albumin \(<\) 3.8 g/dL; serum Prealbumin \(<\) 30 mg/dL for dialysis patients or according to residual renal function for patients with CKD stages 2-5; serum cholesterol \(<\) 100 mg/dL \\ BMI \(<\) 20 kg/m\({}^{2}\) if 70 years of age & Dietary PI \(<\) 0.8 g/kg/day for at least two months for dialysis patients or \\ \(<\) 22 kg/m\({}^{2}\) if \(>\) 70 years of age & \(<\) 0.6 g/kg/day for patients with CKD stages 2-5. Unintentional energy intake \\ FFMI \(<\) 15\% and 17\% kg/m\({}^{2}\) in women and men, respectively & \(<\) 25 kcal/kg/day for at least two months \\  & MM 5\% reduction over three months or 10\% over six months; reduction of \\  & & creatinine appearance \\ \hline FFMI: free fat mass index; MM: muscle mass; MAMC: mid-arm circumference MAMC area \(>\) 10\% in relation to 50 th percentile of reference population; PI: protein intake. \\ \hline \hline \end{tabular}
\end{table}
Table 1: Diagnostic criteria for malnutrition and protein-energy wasting in CKD patients.