C-reactive protein and IL-6: new marker proteins for the diagnosis of CJD in plasma?

Abstract

CJD is usually diagnosed by clinical and neuropathological findings. A number of proteins regarded as markers for neuronal damage in plasma or serum have recently been described. Markers typical for tissue damage, although not usually associated with CJD, are another possibility. An evaluation of the relative usefulness of markers of neuronal and tissue damage in identifying CJD could be beneficial. Plasma samples were collected from 46 patients with sporadic CJD and from a control group of 42 healthy subjects. The samples were analyzed with tests that were specific for C-reactive protein (CRP), IL-6, neuron-specific enolase (NSE), S-100 proteins, and cellular prion protein (PrP(c)). The results were compared, and a cutoff level for each test used was defined as the 90th percentile from the control group. The assay specific for NSE identified only 13 percent of the sporadic CJD patients as positive. The identification rate of the other markers was significantly higher: S-100, 76.1 percent; PrP(c), 76.1 percent; CRP, 78.3 percent; and IL-6, 73.3 percent. Only three of the samples were positive in all five tests. The markers for tissue damage, CRP and IL-6, are as useful as the previously described markers for neuronal damage in the diagnosis of CJD in plasma. All the markers tested are, however, of only limited value in the diagnosis of CJD in plasma. A combination of all surrogate markers improves the specificity but still provides no definitive diagnosis of the disease.