H Zetterberg1,2, N Mattsson3. 1. Clinical Neurochemistry Laboratory, Institute of Neuroscience and Physiology, Sahlgrenska Academy at the University of Gothenburg, Mölndal, Sweden. henrik.zetterberg@gu.se. 2. UCL Institute of Neurology, Queen Square, London, UK. henrik.zetterberg@gu.se. 3. Clinical Memory Research Unit, Lund University, Lund, Sweden.