title: The reliability of the Glasgow Coma Scale: a systematic review.
abstract: BACKGROUND
  The Glasgow Coma Scale (GCS) provides a structured method for assessment of the level of consciousness. Its derived sum score is applied in research and adopted in intensive care unit scoring systems. Controversy exists on the reliability of the GCS. The aim of this systematic review was to summarize evidence on the reliability of the GCS.
  
  
  METHODS
  A literature search was undertaken in MEDLINE, EMBASE and CINAHL. Observational studies that assessed the reliability of the GCS, expressed by a statistical measure, were included. Methodological quality was evaluated with the consensus-based standards for the selection of health measurement instruments checklist and its influence on results considered. Reliability estimates were synthesized narratively.
  
  
  RESULTS
  We identified 52 relevant studies that showed significant heterogeneity in the type of reliability estimates used, patients studied, setting and characteristics of observers. Methodological quality was good (n = 7), fair (n = 18) or poor (n = 27). In good quality studies, kappa values were ≥0.6 in 85%, and all intraclass correlation coefficients indicated excellent reliability. Poor quality studies showed lower reliability estimates. Reliability for the GCS components was higher than for the sum score. Factors that may influence reliability include education and training, the level of consciousness and type of stimuli used.
  
  
  CONCLUSIONS
  Only 13% of studies were of good quality and inconsistency in reported reliability estimates was found. Although the reliability was adequate in good quality studies, further improvement is desirable. From a methodological perspective, the quality of reliability studies needs to be improved. From a clinical perspective, a renewed focus on training/education and standardization of assessment is required.
authors.affiliation: Department of Neurosurgery, Antwerp University Hospital, Wilrijkstraat 10, 2650, Edegem, Belgium. florence.reith@uza.be.|University of Antwerp, Edegem, Belgium. florence.reith@uza.be.
authors.forename: Florence C M
authors.initials: FC
authors.lastname: Reith
authors.affiliation: Department of Neurosurgery, Antwerp University Hospital, Wilrijkstraat 10, 2650, Edegem, Belgium.|University of Antwerp, Edegem, Belgium.
authors.forename: Ruben
authors.initials: R
authors.lastname: Van den Brande
authors.affiliation: Australian & New Zealand Intensive Care Research Centre (ANZIC-RC), School of Public Health and Preventive Medicine, Monash University, Melbourne, Australia.|Cochrane Consumers and Communication Review Group, Centre for Health Communication and Participation, School of Psychology and Public Health, La Trobe University, Melbourne, Australia.|ANZIC-RC, Department of Epidemiology and Preventive Medicine, Monash University, The Alfred Hospital, Level 6, 99 Commercial Road, Melbourne, VIC, 3004, Australia.
authors.forename: Anneliese
authors.initials: A
authors.lastname: Synnot
authors.affiliation: Central Clinical School, Monash University, Melbourne, Australia.|Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore.|Central Clinical School, Level 6, The Alfred Centre, 99 Commercial Road, Melbourne, VIC, 3004, Australia.
authors.forename: Russell
authors.initials: R
authors.lastname: Gruen
authors.affiliation: Department of Neurosurgery, Antwerp University Hospital, Wilrijkstraat 10, 2650, Edegem, Belgium.|University of Antwerp, Edegem, Belgium.
authors.forename: Andrew I R
authors.initials: AI
authors.lastname: Maas
mesh_terms: D016206:Databases, Bibliographic; D019317:Evidence-Based Medicine; D015600:Glasgow Coma Scale / Q000592:standards / Q000706:statistics & numerical data*; D006801:Humans; D015588:Observer Variation; D011237:Predictive Value of Tests; D015203:Reproducibility of Results
keywords: Glasgow Coma Scale; Glasgow Coma Score; Grading scales; Reliability; Reproducibility of results; Systematic review