Microinflammation versus inflammation in chronic renal failure patients

To the Editor: In their study, Pupim et al1.Pupim L.B. Himmelfarb J. McmONAGLE E. et al.Influence of initiation of maintenance hemodialysis on biomarkers of inflammation and oxidative stress.Kidney Int. 2004; 65: 2371-2379Google Scholar show that patients with end-stage renal failure (ESRF) in the highest quartile of C-reactive protein (CRP) and interleukin-6 (IL-6) before hemodialysis (HD) initiation have a significant decrease in the serum level of both markers after 12 months of HD treatment. The baseline levels for IL-6 and CRP in these subgroups were about 58 pg/mL and 62 mg/L, respectively. As the authors note, no exclusion criteria were used for enrollment in the study. These CRP and IL-6 serum levels are probably indicative of an infection or other cause of “real inflammation” (trauma, malignancy, etc.). In the referred study microinflammation investigation is warranted. It is low-grade inflammation that is correlated to atherosclerosis or other threatening processes. Recently, a cut-off for CRP (10 mg/L) indicative for inflammation versus microinflammation was established for the general population2.Pearson T.A. Mensah G.A. Wayne A.R. et al.Markers of inflammation and cardiovascular disease.Circulation. 2003; 107: 499-511Google Scholar. We also found a similar cut-off for CRP and IL-6 (9.5 mg or pg/L) indicative for an inflammatory clinical event, in a group of HD patients3.Tsirpanlis G. Bagos P. Ioannou D. et al.Exploring inflammation in hemodialysis patients: Persistent and superimposed inflammation. A longitudinal study.Kidney Blood Press Res. 2004; 27: 63-70Google Scholar. Possibly this cut-off is higher in other HD patients, but, as the results in the majority of studies with ESRF patients show, it seems improbable to be higher than 15 mg/L for the CRP. The study of Pupim et al is very interesting; it shows convincingly, for the first time, that HD may not be a principal cause of inflammation and oxidative stress in ESRF patients. Although possibly the results are not essentially influenced from the above-mentioned observation, accurate assessment4.Tsirpanlis G. Bagos P. Ioannou D. et al.The variability and accurate assessment of the microinflammation in hemodialysis patients.Nephrol Dial Transplant. 2004; 19: 150-157Google Scholar and distinction between microinflammation and inflammation is needed in all studies in this research field.