## 2 Monitoring of Nutritional Status in CKD Patients: Affected Parameters
### Main Nutritional Score Evaluations  
The majority of the above-described methods, however, are expensive, cumbersome and not suitable for use in routine follow-up in hemodialysis patients. The mini nutritional assessment (MNA) consists in both a shortened form six-item screening tool (MNA-SF) and a full-length 18-item scale (MNA-LF). The full-length tool comprises 18 items aimed at evaluating a range of aspects: BMI, weight loss, arm and calf circumferences; lifestyle, medication, mobility and presence of signs of depression or dementia; brief dietary assessment and subjective assessment. Using the MNA, three specific groups are identified: MNA \(<\) 17 indicating malnourished patients, MNA 17-23.5 patients at risk of malnutrition and \(\geq\) 24 normal nutritional status [58]. A study conducted by [PERSON] et al. indicated MNA-SF as an appropriate and feasible tool for use in identifying nutritional problems in dialysis patients [59]. However, previous studies [60; 61] had cast doubt on the reliability of SGA, malnutrition inflammation score (MIS) and (MNA). When applied to elderly patients, these methods are subject to limitations related to aging (e.g., memory loss, poor compliance, disinformation, etc.). This review also addresses the growing concerns over bias in the estimation of nutritional intake and the possibility that differential bias moves with stratification variables of analytical interest. Inaccuracies arising from the dietary recall of HD patients have long been an acknowledged issue, thus advising against use of this method on dialysis wards due to the high potential for error in dietary assessments, particularly relating to protein intake and calculation of energy expenditure [62]. Conversely, protein intake may be assessed indirectly, particularly in patients on a thrice weekly hemodialysis regimen, by calculating the protein catabolic rate obtained from the percentage or logarithmic variation between pre- and post-dialysis urea nitrogen values. However, it is imperative that HD patients are evaluated in a metabolic steady state, excluding acute or chronic intercurrent pathologies and therapies which may add to dialysis-induced hypercatabolism, thus rendering calculations unreliable [63; 64; 65]. In the case of HD patients on a once or twice weekly hemodialysis regimen who maintain residual diuresis with minimal residual kidney function (RKF), a new and efficient mathematical calculation algorithm is available for practical application of urea kinetic modeling. This is a freely distributed and open-source JavaScript tool called Solute Solver, derived from 35 dialysis and anthropometric parameters which may be applied to evaluate the normalized protein catabolic rate (nPCR) [66]. Another difficult parameter to calculate is resting energy expenditure (REE), particularly as HD patients have a higher REE adjusted for muscle mass than healthy controls. Body composition should also be determined and hypercatabolism taken as a reliable indicator of malnutrition [67]. Furthermore, REE is not influenced by the degree of renal function, although may be elevated during subclinical inflammation typical of hemodialysis patients [68; 69]. In restoring the patient to initial dry weight, several proposed equations fail to take into account body temperature elevation during routine HD [70] or energy required for vasoconstriction to prevent fall in blood pressure as a result of a reduced water volume following loss through ultrafiltration. It should be underlined how this phenomenon is amplified in acetate hemodialysis where energy is needed for the conversion of acetate into bicarbonate by the muscles [71; 72]. Dual-energy X-ray absorptiometry (DXA), based on the signals provided by two energy sources to provide a three-compartment model of body composition, has become the gold standard test [73]. DXA is a reproducible and reliable technique used to measure fat mass in healthy people, as well as in HD patients.