[C-reactive protein in the assessment of iron status in patients on hemodialysis]

Iron availability is a prerequisite for an efficient hematopoietic response to erythropoietin. Dynamic evaluation of iron status is difficult in hemodialysis patients and can be further complicated by the presence of an inflammatory state. Several cytokines, in particular interleukin 6 (IL-6), stimulate the production of hepcidin in the liver. This hormone is the main regulator of the extracellular iron concentration through its effect on the iron channel ferroportin, present in several cell types. IL-6 is also the major stimulus for the production of C-reactive protein (CRP), a nonspecific but sensitive marker of inflammation. Measurement of hepcidin is technically difficult and has so far been limited to research. On the other hand, measurement of CRP, which is both sensitive and easily measurable with automated techniques, might possibly be used as a surrogate measure of iron status in hemodialysis patients. Several studies have suggested the value of CRP in this context, but they dealt with small patient groups and single-time-point measurements. Even the definition of normal values of CRP in dialysis patients is uncertain. During the period between 2003 and 2007, we performed 8322 measurements of CRP in 401 hemodialysis patients followed for 3-60 months. All parameters of iron balance (serum iron, TSAT, percent hypochromic RBC and Hgb concentration in reticulocytes) were clearly affected by the presence of an inflammatory state. We believe that measurement of CRP must be part of the routine hematological assessment of hemodialyzed patients to allow the correct interpretation of data in anemia treatment.