Background: The diagnosis of Creutzfeldt-Jakob disease (CJD) is based on clinical and electroencephalographic criteria which do not allow a reliable diagnosis to be made during life.
Methods: Serum and cerebrospinal fluid (CSF) samples were obtained after informed consent from relatives of suspected cases of CJD referred to the German CJD surveillance unit. CSF samples from 58 definite (neuropathologically verified), 46 probable, and 34 possible CJD cases, and from 44 patients without CJD were analysed by two-dimensional gel electrophoresis (2-DE). Two investigators blinded to clinical findings recorded the presence of two proteins, p130/131. The kappa value for the level of agreement between these investigators was calculated. Results obtained were compared with the determination of neuron-specific enolase (NSE) in CSF. NSE concentrations of more than 35 ng/mL were considered indicative of CJD.
Findings: p130/131 was detected in 81% of definite (47/58), 80% of probable (37/46), 68% of possible (23/34) CJD cases, and in none of the other 44 cases. NSE concentrations of more than 35 ng/mL were seen in 79% of definite (46/58), 80% of probable (37/46), 59% of possible (20/34) CJD cases, and 9% of other cases (4/43). The positive predictive value for 2-DE of CSF is 100% and the negative predictive value is 69%. The level of agreement for the detection of p130/131 by two evaluators in a subset of 141 2-DE gels was a kappa of 0.93 (95% CI 0.86-0.99). Of 13 cases initially classified as possible and later reclassified as definite, ten cases were identified correctly by the 2-DE analysis, indicating a better diagnostic accuracy of this test compared with the current clinical classification. None of nine cases classified as other by neuropathology had p130/131 in 2-DE.
Interpretation: 2-DE for p130/131 is a specific test for the diagnosis of CJD. These data suggest including detection of p130/131 as a criterion for the diagnosis of probable CJD in addition to the currently accepted criteria of a rapidly progressive dementia of less than 2 years duration, typical neurological signs, and periodic sharp-wave complexes in the EEG.