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Observer variation in the assessment of outcome in traumatic brain injury : experience from a multicenter , international randomized clinical trial . OBJECTIVE Accurate and consistent outcome assessment is essential to randomized clinical trials . We aimed to explore observer variation in the assessment of outcome in a recently completed trial of dexanabinol in head injury and to consider steps to reduce such variation . METHODS Eight hundred sixty-one patients with severe traumatic brain injury who were admitted to 86 centers were included in a multicenter , placebo-controlled , Phase III trial . Outcome was assessed at 3 and 6 months postinjury using the extended Glasgow Outcome Scale ; standardized assessment was facilitated by the use of a structured interview . Before initiation of trial centers , outcome ratings were obtained for sample cases to establish initial levels of agreement . Training sessions in outcome assessment were held , and problems in assigning outcome were investigated . During the trial , a process of central review was established to monitor performance . Interobserver variation was analyzed using the kappa statistic . RESULTS Substantial observer variation was found in the rating of sample cases ( weighted kappa , 0.72 ; confidence interval , 0.68-0.75 ) and in assigning outcome based on completed structured interviews ( weighted kappa , 0.61 ; confidence interval , 0.57-0.64 ) . In the early stages of the trial , a relatively large number of discrepancies ( 29-37 % ) were identified on central review . This number declined as the trial progressed and coincided with investigator training and feedback from central review . Centers with higher enrollment rates showed better performance . CONCLUSION Observer variation in outcome assessment is a significant problem for head injury trials . Consistency can be improved by standardizing procedures , training assessors , and monitoring the quality of assessments and providing feedback to interviewers .
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Intervention_Pharmacological
dexanabinol
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Intervention_Control
placebo-controlled
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Outcome_Other
assessment of outcome
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Outcome_Other
outcome assessment
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Outcome_Other
assessment of outcome
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Outcome_Physical
extended Glasgow Outcome Scale ;
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Outcome_Other
outcome ratings
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Outcome_Other
Substantial observer variation
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Outcome_Other
outcome
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Outcome_Other
discrepancies
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Outcome_Other
Observer variation
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Outcome_Other
outcome assessment
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Outcome_Other
Consistency
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Participant_Condition
head injury
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Participant_Sample-size
Eight hundred sixty-one patients
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Participant_Condition
severe traumatic brain injury