1 University of Leuven, Leuven, Belgium; University College London, London, UK.
2 Ludwig-Maximilians-Universität München, Munich, Germany; German Center for Neurodegenerative Diseases, Munich, Germany.
3 University College London, London, UK.
4 University College London, London, UK; University of Gothenburg, Gothenburg 405 30, Sweden; University of Wisconsin-Madison, Madison, WI, USA. Electronic address: henrik.zetterberg@clinchem.gu.se.