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.
FINDINGS: 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).
INTERPRETATION: The Salzburg criteria for diagnosis of NCSE have high diagnostic 
accuracy and excellent inter-rater agreement, making them suitable for 
implementation in clinical practice.
FUNDING: None.