Reliability of Postal Questionnaires for the Glasgow Outcome Scale

Abstract

The purpose of the study was to investigate if a questionnaire sent by mail can give a reliable assessment of outcome on the Glasgow Outcome Scale. A questionnaire was developed for the Glasgow Outcome Scale (GOS) and a second questionnaire for the Extended Glasgow Outcome Scale (GOSE). The questionnaires were self-contained and designed to be completed by either a head-injured person or a proxy. The questionnaires were studied in two ways: each questionnaire was administered twice (at an interval of approximately 2 weeks), and ratings from the postal questionnaires were compared to ratings from a structured interview conducted by telephone. The four studies were carried out in separate groups of head-injured participants consisting of 32-38 individuals. For the test-retest comparison, k(w) (quadratic weights) was 0.94 for the GOS questionnaire and 0.98 for the GOSE questionnaire. For the comparison with the telephone interview, k(w) was 0.67 for the GOS and 0.92 for the GOSE. The values of k(w) indicate good agreement for all comparisons. We conclude that it is possible to obtain reliable outcome data after head injury using postal questionnaires.

The Glasgow Outcome Scale — 40 years of application and refinement

“…High levels of agreement were seen between telephone and face-to face administration (test-retest GOS kappa= 0.92 and GOSE 0.92; inter-rater GOS kappa= 0.85 and GOSE 0.84) 33 . Postal versions of the GOS and the GOSE, which could be completed by the person with head injury or by a proxy, also had very high testretest reliability (kappa= 0.94 GOS and 0.98 GOSE) 34 .…”

Assessment of White Matter Injury and Outcome in Severe Brain Trauma. A Prospective Multicenter Cohort

“…32 Third, we used a modified version of the GOS that has not been independently validated; nevertheless, we believed that this Evaluation of TBI with Diffusion Tensor Imaging modification is essential to account for the fact that the "severe disability" (GOS 3) is inherently heterogeneous. Despite the difficulty of dichotomization, an issue that is intrinsic to much clinical outcome research, it is not a fundamental limitation.…”

The Glasgow Outcome at Discharge Scale: An Inpatient Assessment of Disability after Brain Injury

“…We therefore base the sample size calculation for quadratic-weighted kappa on that for the product-moment correlation coefficient r. Algina and Olejnik 18 provide tables for the product-moment correlation coefficient in terms of the sample size needed to achieve a given width of CI for a range of possible true values of r. Hence, we estimated that about 60 patients were needed for the reliability study and, from previous studies, approximately 80 to assess validity. [6][7][8][9][10] Inter-rater reliability on the GODS was assessed using the quadratic-weighted kappa and 95% CI. Concurrent and convergent validity (association between GODS and each of inpatient DRS and SF-36, respectively) was quantified by the Spearman rank correlation coefficient and 95% CI.…”

“…Both the GOS and GOS-E are simple and quick to administer and are valid and reliable when used in face to face interview, telephone interview, or in amended form by postal return. [6][7][8][9][10] The GOS is not valid in a hospital setting, however, because a key criterion is restitution of independence in society. Despite this, the GOS continues to be used inappropriately in studies on hospitalized patients, emphasizing a demand for an inpatient version.…”