title: Diagnostic accuracy of the Salzburg EEG criteria for non-convulsive status epilepticus: a retrospective study.
abstract: BACKGROUND
  Several EEG criteria have been proposed for diagnosis of non-convulsive status epilepticus (NCSE), but none have been clinically validated. We aimed to assess the diagnostic accuracy of the EEG criteria proposed by a panel of experts at the fourth London-Innsbruck Colloquium on Status Epilepticus in Salzburg, 2013 (henceforth called the Salzburg criteria).
  
  
  METHODS
  We did a retrospective, diagnostic accuracy study using EEG recordings from patients admitted for neurological symptoms or signs to three centres in two countries (Danish Epilepsy Centre, Dianalund, Denmark; Aarhus University Hospital, Aarhus, Denmark; and Paracelsus Medical University, Salzburg, Austria). Participants were included from the Danish centres if they were aged 4 months or older, and from the Austrian centre if aged 18 years or older. Participants were sorted into two groups: consecutive patients under clinical suspicion of having NCSE (the clinical validation group) or consecutive patients with abnormal EEG findings but no clinical suspicion of NCSE (the control group). Two raters blinded to all other patient data retrospectively analysed the EEG recordings and, using the Salzburg criteria, categorised patients as in NCSE or not in NCSE. By comparing with a reference standard inferred from all clinical and para-clinical data, therapeutic response, and the final outcome, we calculated sensitivity, specificity, overall diagnostic accuracy, positive and negative predictive values, and inter-rater agreement for the Salzburg criteria. The reference standard was inferred by two raters who were blinded to the scorings of the Salzburg criteria.
  
  
  RESULTS
  We retrospectively reviewed EEG data from 220 patients. EEGs in the clinical validation group were recorded in 120 patients between Jan 1, and Feb 28, 2014 (Austria), and Aug 1, 2014, and Jan 31, 2015 (Denmark). EEGs in the control group were recorded in 100 patients between Jan 13 and Jan 22, 2014 (Austria) and Jan 12 and Jan 26, 2015 (Denmark). According to the reference standard, 43 (36%) of the 120 patients in the validation group had NCSE. In the validation cohort sensitivity was 97·7% (95% CI 87·9-99·6) and specificity was 89·6% (80·8-94·6); overall accuracy was 92·5% (88·3-97·5). Positive predictive value was 84·0% (95% CI 74·1-91·5) and negative predictive value was 98·6% (94·4-100). Three people in the control group (n=100) fulfilled the Salzburg criteria and were therefore false positives (specificity 97·0%, 95% CI 91·5-99·0; sensitivity not calculable). Inter-rater agreement was high for both the Salzburg criteria (k=0·87) and for the reference standard (k=0·95). Therapeutic changes occurred significantly more often in the group of patients fulfilling Salzburg criteria (42 [84%] of 50 patients) than in those who did not (11 [16%] of 70; p<0·0001).
  
  
  CONCLUSIONS
  The Salzburg criteria for diagnosis of NCSE have high diagnostic accuracy and excellent inter-rater agreement, making them suitable for implementation in clinical practice.
  
  
  BACKGROUND
  None.
authors: Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University, Salzburg, Austria; Centre for Cognitive Neuroscience Salzburg, Austria.
authors: Markus
authors: M
authors: Leitinger
authors: Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University, Salzburg, Austria; Centre for Cognitive Neuroscience Salzburg, Austria.
authors: Eugen
authors: E
authors: Trinka
authors: Department of Clinical Neurophysiology, Danish Epilepsy Centre, Dianalund, Denmark; Institute of Regional Health Research, University of Southern Denmark, Odense, Denmark.
authors: Elena
authors: E
authors: Gardella
authors: Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University, Salzburg, Austria; Centre for Cognitive Neuroscience Salzburg, Austria.
authors: Alexandra
authors: A
authors: Rohracher
authors: Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University, Salzburg, Austria; Centre for Cognitive Neuroscience Salzburg, Austria.
authors: Gudrun
authors: G
authors: Kalss
authors: Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark.
authors: Erisela
authors: E
authors: Qerama
authors: Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University, Salzburg, Austria; Centre for Cognitive Neuroscience Salzburg, Austria.
authors: Julia
authors: J
authors: Höfler
authors: Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark.
authors: Alexander
authors: A
authors: Hess
authors: Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University, Salzburg, Austria; Centre for Cognitive Neuroscience Salzburg, Austria.
authors: Georg
authors: G
authors: Zimmermann
authors: Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University, Salzburg, Austria; Centre for Cognitive Neuroscience Salzburg, Austria; Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria.
authors: Giorgi
authors: G
authors: Kuchukhidze
authors: Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University, Salzburg, Austria; Centre for Cognitive Neuroscience Salzburg, Austria.
authors: Judith
authors: J
authors: Dobesberger
authors: Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University, Salzburg, Austria; Centre for Cognitive Neuroscience Salzburg, Austria.
authors: Patrick B
authors: PB
authors: Langthaler
authors: Department of Clinical Neurophysiology, Danish Epilepsy Centre, Dianalund, Denmark; Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark. Electronic address: sbz@filadelfia.dk.
authors: Sándor
authors: S
authors: Beniczky
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D004569:Electroencephalography / Q000592:standards*; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D017410:Practice Guidelines as Topic / Q000592:standards*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013226:Status Epilepticus / Q000175:diagnosis*; D055815:Young Adult