Depositions of proteins in form of amyloid and non-amyloid plaques are common pathogenic signs of more than 20 degenerative diseases affecting the central nervous system or a variety of peripheral tissues. Among the neuropathological conditions, Alzheimer's, Parkinson's and the prion diseases, such as Creutzfeldt-Jakob disease (CJD), present ambiguities as regarding their differential diagnosis. At present, their diagnosis must be confirmed by post-mortem examination of the brain. Currently the ante-mortem diagnosis is still based on the integration of multiple data (clinical, paraclinical and biological analyses) because no unique marker exists for such diseases. The detection of specific biomarkers would be useful to develop a differential diagnostic, distinguishing not only different neurodegenerative diseases but also the disease from the non-pathological effects of aging. Several neurodegenerative biomarkers are present at very low levels during the early stages of the disease development and their ultra-low detection is needed for early diagnosis, which should permit more effective therapeutic interventions, before the disease concerned can progress to a stage where considerable damage to the brain has already occurred. In the case of prion diseases, there are concerns regarding not only patient care, but the wider community too, with regard to the risk of transmission of prions, especially during blood transfusion, for which, four cases of variant CJD infection associated with transfusion of non-leukocyte-depleted blood components have been confirmed. Therefore the development of techniques with high sensitivity and specificity represent the major challenge in the field of the protein misfolding diseases. In this paper we review the current analytical and/or biochemical diagnostic technologies used mainly in prion, but also in Alzheimer and Parkinson diseases and emphasizing work on the protein detection as a surrogates and specific biomarker in the body fluid of patients (urine, CSF and blood). This review highlights the urgency of the development of early and sensitive diagnostics in terms of therapeutic challenge.
