title: Diagnostic performance of cerebrospinal fluid total tau and phosphorylated tau in Creutzfeldt-Jakob disease: results from the Swedish Mortality Registry.
abstract: OBJECTIVE
  Identifying a clinical distinction between the invariably lethal prion disease Creutzfeldt-Jakob disease (CJD) and nonprion rapidly progressive dementias is important and sometimes difficult; thus, reliable tools for diagnosis are in great demand.
  
  
  OBJECTIVE
  To test the diagnostic performance of dementia cerebrospinal fluid (CSF) biomarkers total tau (T-tau), phosphorylated tau (P-tau), and the T-tau to P-tau ratio for CJD by analyzing the results from a large database of routine clinical samples in combination with diagnosis information from the Swedish Mortality Registry.
  
  
  METHODS
  This was a retrospective cohort study. We cross-referenced the Swedish Mortality Registry with a data set of CSF measurements of T-tau and P-tau performed in routine clinical testing at the Clinical Neurochemistry Laboratory of the Sahlgrenska University Hospital, which serves most of Sweden. The data set consisted of 9765 deceased individuals with CSF measures, including 93 with CJD, with 52 autopsy-verified samples (56%).
  
  
  METHODS
  For each patient, T-tau and P-tau levels in CSF were measured and the T-tau to P-tau ratio was calculated. Biomarker levels (adjusted for age and sex) were analyzed in relation to the recorded cause of death and time of death. We specifically tested a previously defined CJD biomarker profile (T-tau >1400 ng/L and T-tau to P-tau-ratio >25).
  
  
  RESULTS
  Patients who died of CJD had elevated CSF T-tau levels and T-tau to P-tau ratio, but not elevated CSF P-tau levels, compared with patients who died of Alzheimer disease (AD) and other dementias. The previously defined biomarker profile had a specificity of 99.0%, a sensitivity of 78.5%, and a positive likelihood ratio of 79.9. When tested against common differential diagnoses, the sensitivity, specificity, and positive likelihood ratio of this profile was 78.5%, 99.6%, and 196.6, respectively, in relation to AD and 78.5%, 99.3%, and 109.3, respectively, in relation to other dementias. In CJD individuals (n = 30) with repeated measurements, but not in those with AD (n = 242) or other dementias (n = 258), T-tau levels and T-tau to P-tau ratios increased over time.
  
  
  CONCLUSIONS
  In this routine clinical setting, the combination of increased T-tau levels and increased T-tau to P-tau ratios in CJD patients has a very high specificity against important differential diagnoses to CJD and may serve as a clinically useful diagnostic test.
authors.affiliation: Clinical Neurochemistry Laboratory, Institute of Neuroscience and Physiology, Department of Neurochemistry, Sahlgrenska Academy, University of Gothenburg, Mölndal, Sweden.
authors.forename: Tobias
authors.initials: T
authors.lastname: Skillbäck
authors.affiliation: Clinical Neurochemistry Laboratory, Institute of Neuroscience and Physiology, Department of Neurochemistry, Sahlgrenska Academy, University of Gothenburg, Mölndal, Sweden.
authors.forename: Christoffer
authors.initials: C
authors.lastname: Rosén
authors.affiliation: Institute of Neuroscience and Physiology, Department of Clinical Neuroscience and Rehabilitation, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Fredrik
authors.initials: F
authors.lastname: Asztely
authors.affiliation: Clinical Neurochemistry Laboratory, Institute of Neuroscience and Physiology, Department of Neurochemistry, Sahlgrenska Academy, University of Gothenburg, Mölndal, Sweden3Center for Imaging of Neurodegenerative Diseases, Department of Veterans Affairs Med.
authors.forename: Niklas
authors.initials: N
authors.lastname: Mattsson
authors.affiliation: Clinical Neurochemistry Laboratory, Institute of Neuroscience and Physiology, Department of Neurochemistry, Sahlgrenska Academy, University of Gothenburg, Mölndal, Sweden.
authors.forename: Kaj
authors.initials: K
authors.lastname: Blennow
authors.affiliation: Clinical Neurochemistry Laboratory, Institute of Neuroscience and Physiology, Department of Neurochemistry, Sahlgrenska Academy, University of Gothenburg, Mölndal, Sweden5University College London Institute of Neurology, London, England.
authors.forename: Henrik
authors.initials: H
authors.lastname: Zetterberg
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000134:cerebrospinal fluid; D015331:Cohort Studies; D007562:Creutzfeldt-Jakob Syndrome / Q000134:cerebrospinal fluid / Q000175:diagnosis* / Q000401:mortality*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D010766:Phosphorylation / Q000235:genetics; D012042:Registries; D012189:Retrospective Studies; D015996:Survival Rate / Q000639:trends; D013548:Sweden / Q000453:epidemiology; D016875:tau Proteins / Q000134:cerebrospinal fluid*
chemical_list: D015415:Biomarkers; D016875:tau Proteins