Table 5.

Nutritional evaluation in dialysis patients: some advantages and limits of the common tests.

	Suggested Frequency	Advantages	Limits
Anthropometry
Body weight (b.w.) Middle arm circumference Triceps skinfold thickness Skeletal muscle circumference	Each treatment Monthly Monthly Monthly Monthly	Non-invasive, provides immediate results, easily compared in different settings.	Precise measurements need a skilled operator and are relatively demanding in terms of time.
Body composition
Bio-impedance analysis (BIA)	Monthly for body composition up to each treatment to evaluate fluid overload.	Non-invasive, provides immediate results, easily compared in different settings.	BIA should be performed at least 15 min after the end of the dialysis; patients may be reluctant to wait; the cost of the electrodes is relatively high. Difficult to standardize in patients with amputation or skin problems. Has to be interpreted with caution in obese of anorectic patients.
Biochemical data
Serum albumin Total proteins Transferrin Prealbumin Glucose Lipids Protein nitrogen Appearance (PNA) Lymphocyte count Liver enzymes	Monthly	Valuable tools to assess effective dietary intake and adherence to dietary prescriptions	All the main nutritional markers are affected not only by the nutritional status but also by dialysis efficiency, type of dialysis (hemodialysis vs. hemodiafiltration) and by the inflammatory status. Interpretation may be difficult, particularly in patients at high comorbidity.
Evaluation scales
Subjective Global Assessment (SGA) Malnutrition Inflammation Score (MIS)	Quarterly Quarterly	Widely used assessment tools for dialysis patients, useful to compare different series.	SGA is very sensible to rapid changes, may be less sensitive to chronic changes. MIS is a mixed marker, taking into account comorbidity and inflammation, The specific weight of nutrition may be difficult to enucleate.
Dietary habits
Dietary recall (usually 24 h) Three days or seven days dietary journal Food frequency questionnaires	At least monthly	The evaluation of dietary habits is the first step to evaluate nutritional intervention as gives qualitative and quantitative information to target nutritional counseling	The recall may be biased or difficult in patients with cognitive impairment. Compliance to dietary journals may be difficult. Food frequency questionnaires are often very sensitive to the cultural context and may be difficult to adapt to a multiethnic population.
Functional Tests
Barthel Index Karnofsky Index	Quarterly Quarterly	Highlight the effect of nutritional status on functional abilities	Indirectly evaluation of nutritional status. Sensitive to the burden of comorbidity.
Performance Tests
6 min walking test 30′ Sit-to-stand-to-sit Hand-Grip test	Quarterly Quarterly Quarterly	Useful to monitor the effects of a nutritional intervention; hand-grip test is increasingly used to evaluate force as an indirect measure of muscle mass.	The tests are reliable only in experienced hands. Hand grip tests may be performed in different ways, and may be affected by the presence of an arterio-venous fistula or graft.