Predictive and diagnostic factors of malnutrition in hemodialysis patients

The relationship between malnutrition and inflammation is by now well established. IL-6 and, probably, other proinflammatory cytokines (mainly IL-1 and TNF) may represent the link between these two entities since these interleukins may promote loss of appetite, muscle protein breakdown and reduced hepatic synthesis of "negative" acute phase proteins like albumin, prealbumin and transferrin. IL-6 also stimulates up to 1000 fold the hepatic synthesis of "positive" acute phase proteins, mainly C-reactive Protein (CRP) and Serum Amyloid A. The association between CRP and cardiovascular mortality in the general population, as well as in haemodialysed uraemic patients, is well established. These crucial interrelationships have modified the interpretation of serum albumin concentration in the diagnosis of malnutrition; a reduced serum albumin concentration, in fact, in the presence of high CRP values should point towards a diagnosis of inflammation, though the inflammation may often induce weight loss or a condition of malnutrition. After switching most patients to a more biocompatible dialysis membrane and improvement of the quality of the dialysis fluid (by adopting hydrophobic filters at the water entry of dialysis devices and bicarbonate powder cartridges) nephrologists have focused their attention on other sources of inflammation (e.g. artificial vascular protheses, presence of infected thrombi, Clamidiae, Helicobacter Pilori, dental granulomas etc.). Starting from these assumptions the diagnosis of malnutrition, once focused mainly on serum albumin reduction, must be based on other parameters (clinical history of body mass wasting, dietary and anthropometric assessment, subjective global assessment, bioimpedance analysis etc.). All these investigations, however, must be examined together to obtain suitable information on the risk of malnutrition in dialysis patients. A comprehensive approach to malnutrition-inflammation in dialysis patients is the object of the present nephrology conference.