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Centre for Evidence-
Based Medicine

Were objective outcome criteria applied in a "blind" fashion?

We need to assess whether and how explicit criteria for each outcome of interest were applied and if there is evidence that they were applied without knowledge of the prognostic factors under consideration. Blinding is crucial if any judgement is required to assess the outcome because unblinded investigators may search more aggressively for outcomes in people with the characteristic(s) felt to be of prognostic importance than in other individuals. Blinding may be unnecessary if the assessments are preplanned for all patients and/or are unequivocal, such as total mortality. However, judging the underlying cause of death is difficult and requires blinding to the presence of the risk factor to ensure that it is unbiased.

In the study we identified, patients were asked at follow-up if they had a seizure and if they said "yes", a study neurologist subsequently assessed them. It is unclear if the study neurologist was "blind".

  1. Was a defined, representative sample of patients assembled at a common (usually early) point in the course of their disease?
  2. Was patient follow-up sufficiently long and complete?
  3. Were objective outcome criteria applied in a "blind" fashion?
  4. If subgroups with different prognoses are identified: