Inter-Laboratory Assessment of PrPSc Typing in Creutzfeldt-Jakob Disease: A Western Blot Study within the NeuroPrion Consortium

Molecular typing is of considerable importance for the surveillance and epidemiology of human transmissible spongiform encephalopathies (TSEs). It relies on the detection of distinct protease-resistant prion protein (PrPSc) core fragments that differ in molecular mass and/or glycoform ratio. In this collaborative study, we tested the inter-laboratory agreement in TSE molecular typing. Sixteen characterized brain specimens from sporadic TSEs and variant Creutzfeldt-Jakob disease (vCJD) cases were distributed blindly to seven laboratories for molecular characterization by a defined protocol and classification. Agreement between laboratories in the classification of samples was excellent. In particular, there were no differences in the distinction between PrPSc type 1, type 2A, and type 2B with one exception, which eventually was identified as a case with types 1 and 2 co-occurrence. This shows that the general technique and particular classification system used here are robust and represent a reliable basis for diagnostic and epidemiologic purposes. The subtle further distinction of subtypes among type 1 and type 2 groups requires high-sensitivity gel electrophoresis protocols that are unsuitable for routine diagnostic needs and must be reserved for research investigations. Further research is necessary on the identification and significance of co-occurrence of PrPSc types 1 and 2 within one brain.