CRP measurement: does the assay matter in hemodialysis patients?

Background: The serum level of C-reactive protein, an acute-phase marker of systemic inflammation, has been shown to predict cardiovascular events in the general population and cardiovascular and total mortality in hemodialysis patients. High-sensitivity CRP assays (hs-CRP) have been used in numerous studies. We hypothesized that the level of CRP as measured by the conventional assay (c-CRP) would predict mortality in hemodialysis patients with an accuracy similar to that of high-sensitivity assays. Methods: In April 2001 CRP serum level was measured with both a conventional and a high-sensitivity assay in 102 prevalent hemodialysis patients. Mortality was prospectively monitored over 6 years. Results: 49 patients (48%) died during follow-up. With both assays, almost 2/3 of patients had high CRP levels (> 1 mg/dl). Survival at 6 years was significantly lower in patients with high CRP levels, no matter which assay was used (31.5% for patients with high hs-CRP and 27.3% for patients with high c-CRP vs 48.4% for patients with low hs-CRP and 47.1% for patients with low c-CRP). Cardiovascular mortality was also higher in patients with high CRP levels, whatever the type of assay (conventional or high sensitivity) used. The correlation between the two tests was excellent. Conclusion: CRP level, measured by a conventional inexpensive assay, is predictive of mortality in hemodialysis patients.