Misclassification and treatment effect on primary outcome measures in clinical trials of severe neurotrauma

Long-Term Outcomes in Severe Traumatic Brain Injury and Associated Factors: A Prospective Cohort Study

OBJECTIVE

The presence of focal lesion (FL) after a severe traumatic brain injury is an important factor in determining morbidity and mortality. Despite this relevance, few studies show the pattern of recovery of patients with severe traumatic brain injury (TBI) with FL within one year. The objective of this study was to identify the pattern of recovery, independence to perform activities of daily living (ADL), and factors associated with mortality and unfavorable outcome at six and twelve months after severe TBI with FL.

METHODOLOGY

This is a prospective cohort, with data collected at admission, hospital discharge, three, six, and twelve months after TBI.

RESULTS

The study included 131 adults with a mean age of 34.08 years. At twelve months, 39% of the participants died, 80% were functionally independent by the Glasgow Outcome Scale Extended, 79% by the Disability Rating Scale, 79% were independent for performing ADLs by the Katz Index, and 53.9% by the Lawton Scale. Report of alcohol intake, sedation time, length of stay in intensive care (ICU LOS), Glasgow Coma Scale, trauma severity indices, hyperglycemia, blood glucose, and infection were associated with death. At six and twelve months, tachypnea, age, ICU LOS, trauma severity indices, respiratory rate, multiple radiographic injuries, and cardiac rate were associated with dependence.

CONCLUSIONS

Patients have satisfactory functional recovery up to twelve months after trauma, with an accentuated improvement in the first three months. Clinical and sociodemographic variables were associated with post-trauma outcomes. Almost all victims of severe TBI with focal lesions evolved to death or independence.

A Manual for the Glasgow Outcome Scale-Extended Interview

The Glasgow Outcome Scale-Extended (GOSE) has become one of the most widely used outcome instruments to assess global disability and recovery after traumatic brain injury. Achieving consistency in the application of the assessment remains a challenge, particularly in multi-center studies involving many assessors. We present a manual for the GOSE interview that is designed to support both single- and multi-center studies and promote inter-rater agreement. Many patients fall clearly into a particular category; however, patients may have outcomes that are on the borderline between adjacent categories, and cases can present other challenges for assessment. The Manual includes the general principles of assessment, advice on administering each section of the GOSE interview, and guidance on "borderline" and "difficult" cases. Finally, we discuss the properties of the GOSE, including strengths and limitations, and outline recommendations for assessor training, accreditation, and monitoring.

Central Curation of Glasgow Outcome Scale-Extended Data: Lessons Learned from TRACK-TBI

The Glasgow Outcome Scale (GOS) in its original or extended (GOSE) form is the most widely used assessment of global disability in traumatic brain injury (TBI) research. Several publications have reported concerns about assessor scoring inconsistencies, but without documentation of contributing factors. We reviewed 6801 GOSE assessments collected longitudinally, across 18 sites in the 5-year, observational Transforming Research and Clinical Knowledge in TBI (TRACK-TBI) study. We recorded error rates (i.e., corrections to a section or an overall rating) based on site assessor documentation and categorized scoring issues, which then informed further training. In cohort 1 (n = 1261; February 2014 to May 2016), 24% of GOSEs had errors identified by central review. In cohort 2 (n = 1130; June 2016 to July 2018), acquired after curation of cohort 1 data, feedback, and further training of site assessors, the error rate was reduced to 10%. GOSE sections associated with the most frequent interpretation and scoring difficulties included whether current functioning represented a change from pre-injury (466 corrected ratings in cohort 1; 62 in cohort 2), defining dependency in the home and community (163 corrections in cohort 1; three in cohort 2) and return to work/school (72 corrections in cohort 1; 35 in cohort 2). These results highlight the importance of central review in improving consistency across sites and over time. Establishing clear scoring criteria, coupled with ongoing guidance and feedback to data collectors, is essential to avoid scoring errors and resultant misclassification, which carry potential to result in "failure" of clinical trials that rely on the GOSE as their primary outcome measure.

Ordinal outcome analysis improves the detection of between-hospital differences in outcome

Background

There is a growing interest in assessment of the quality of hospital care, based on outcome measures. Many quality of care comparisons rely on binary outcomes, for example mortality rates. Due to low numbers, the observed differences in outcome are partly subject to chance. We aimed to quantify the gain in efficiency by ordinal instead of binary outcome analyses for hospital comparisons. We analyzed patients with traumatic brain injury (TBI) and stroke as examples.

Methods

We sampled patients from two trials. We simulated ordinal and dichotomous outcomes based on the modified Rankin Scale (stroke) and Glasgow Outcome Scale (TBI) in scenarios with and without true differences between hospitals in outcome. The potential efficiency gain of ordinal outcomes, analyzed with ordinal logistic regression, compared to dichotomous outcomes, analyzed with binary logistic regression was expressed as the possible reduction in sample size while keeping the same statistical power to detect outliers.

Results

In the IMPACT study (9578 patients in 265 hospitals, mean number of patients per hospital = 36), the analysis of the ordinal scale rather than the dichotomized scale (‘unfavorable outcome’), allowed for up to 32% less patients in the analysis without a loss of power. In the PRACTISE trial (1657 patients in 12 hospitals, mean number of patients per hospital = 138), ordinal analysis allowed for 13% less patients. Compared to mortality, ordinal outcome analyses allowed for up to 37 to 63% less patients.

Conclusions

Ordinal analyses provide the statistical power of substantially larger studies which have been analyzed with dichotomization of endpoints. We advise to exploit ordinal outcome measures for hospital comparisons, in order to increase efficiency in quality of care measurements.

Trial registration

We do not report the results of a health care intervention.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12874-020-01185-7.

Functional Status Examination Yields Higher Measurement Precision of Functional Limitations after Traumatic Injury than the Glasgow Outcome Scale-Extended: A Preliminary Study

The Glasgow Outcome Scale-Extended (GOSE) is one of the most widely used measures of functional limitations after traumatic brain injury (TBI), and is the primary outcome measure used in clinical trials of acute TBI treatment. However, the GOSE appears insensitive to the full spectrum of TBI-related functional limitations, which may limit its potential to capture treatment effects or correlate with other variables that impact outcome. The Functional Status Examination (FSE) was designed to improve on the assessment of injury-related functional limitations using a standardized assessment and wider possible score range. The aim of this pilot study was to employ item response theory (IRT) to test the hypothesis that the FSE yields more precise estimation of functional outcome than the GOSE. Traumatically injured patients (n = 100, 77 TBI, 23 orthopedic injuries) were interviewed at 3 months post-injury using both the GOSE and FSE structured interviews. IRT was used to quantify and compare the tests' information functions, which reflect the degree to which each instrument precisely measures functional limitations across the severity spectrum. Findings were consistent with predictions: the FSE yielded stronger measurement of functional limitations (i.e., higher test information) across a wider range of severity than the GOSE, whether scoring the GOSE from all interview items or using the traditional GOSE overall score. Although the FSE appears to be a promising alternative measure to the GOSE, further research is needed to cross-validate these findings in a larger sample and understand how to best deploy it in clinical and translational research.

Diagnosing the GOSE: Structural and Psychometric Properties Using Item Response Theory, a TRACK-TBI Pilot Study

The Glasgow Outcome Scale-Extended (GOSE) was designed to assess global outcome after traumatic brain injury (TBI). Since its introduction, several empirically founded criticisms of the GOSE have been raised, including poor reliability; an insensitivity to small, but potentially meaningful, changes; a tendency to produce ceiling effects; inconsistent associations with neurocognitive, psychological, and quality-of-life measures; and an inability to assess the multi-dimensional nature of TBI outcome. The current project took a diagnostic approach to identifying the underlying causes of reported limitations by exploring the internal construct validity of the GOSE at 3 and 6 months post-injury using item response theory (IRT) techniques. Data were from the TRACK-TBI Pilot Study, a large (N = 586), prospective, multi-site project that included TBI cases of all injury severity levels. To assess the level of latent functional "impairment" captured by GOSE items independent of the assigned outcome category or GOSE total score, items were modified so that higher scores reflected greater impairment. Results showed that although the GOSE's items capture varying levels of impairment across a broad disability spectrum at 3 and 6 months, there was also evidence at each time point of item redundancy (multiple items capturing similar levels of impairment), item deficiency (lack of items capturing lower levels of impairment), and item inefficiency (items only capturing minimal impairment information). The findings illustrate the value of IRT to illuminate strengths and weaknesses of clinical outcome assessment measures and provide a framework for future measure refinement.

Functional Status Examination versus Glasgow Outcome Scale Extended as Outcome Measures in Traumatic Brain Injuries: How Do They Compare?

Outcome measures are essential components of natural history studies of recovery and treatment effects after traumatic brain injury (TBI). The Glasgow Outcome Scale (GOS) and its revised version, the Glasgow Outcome Scale Extended (GOSE), are well accepted and widely used for both observational and intervention studies, but there are concerns about their psychometric properties and aptness as outcome measures for TBI. The present study compares the Functional Status Examination (FSE) with the GOSE to assess outcome after TBI in a sample of 533 participants with TBI from the Magnesium Sulfate study and the Transforming Research and Clinical Knowledge in Traumatic Brain Injury (TRACK-TBI) study by evaluating the sensitivity of each measure to severity of brain injury and recovery of function over time. The results indicate that both measures are strongly correlated with TBI severity. At three months, the correlation strengths between injury severity and each outcome measure do not differ (p = 0.88 for Glasgow Coma Scale [GCS], p = 0.13 for computed tomography [CT] abnormalities) but at six months, the FSE is more strongly related to TBI severity indices than is the GOSE (p = 0.045 for GCS, p = 0.014 for CT abnormalities). In addition, the FSE generally shows significantly more improvement over time than the GOSE (p < 0.001). Detailed, structured administration rules and a wider score range of the FSE likely yields more sensitive and precise assessment of functional level than the GOSE. The FSE may be a valuable alternative to the GOSE for assessing functional outcome after TBI.

Validating Multidimensional Outcome Assessment Using the TBI Common Data Elements: An Analysis of the TRACK-TBI Pilot Sample

The Glasgow Outcome Scale-Extended (GOSE) is often the primary outcome measure in clinical trials for traumatic brain injury (TBI). Although the GOSE's capture of global function outcome has several strengths, concerns have been raised about its limited ability to identify mild disability and failure to capture the full scope of problems patients exhibit after TBI. This analysis examined the convergence of disability ratings across a multidimensional set of outcome domains in the Transforming Research and Clinical Knowledge in Traumatic Brain Injury (TRACK-TBI) Pilot study. The study collected measures recommended by the TBI Common Data Elements (CDE) Workgroup. Patients presenting to 3 emergency departments with a TBI of any severity enrolled in TRACK-TBI prospectively after injury; outcome measures were collected at 3 and six months postinjury. Analyses examined frequency of impairment and overlap between impairment status across the CDE outcome domains of Global Level of Functioning (GOSE), Neuropsychological (cognitive) Impairment, Psychological Status, TBI Symptoms, and Quality of Life. GOSE score correlated in the expected direction with other outcomes (M Spearman's rho = .21 and .49 with neurocognitive and self-report outcomes, respectively). The subsample in the Upper Good Recovery (GOSE 8) category appeared quite healthy across most other outcomes, although 19.0% had impaired executive functioning (Trail Making Test Part B). A significant minority of participants in the Lower Good Recovery subgroup (GOSE 7) met criteria for impairment across numerous other outcome measures. The findings highlight the multidimensional nature of TBI recovery and the limitations of applying only a single outcome measure.

Association of Serum Uric Acid Level with the Severity of Brain Injury and Patient's Outcome in Severe Traumatic Brain Injury

INTRODUCTION

The prognostic value of serum Uric Acid (UA) levels in Traumatic Brain Injury (TBI) is unclear.

AIM

To investigate the relationship between serum UA levels and prognosis of patients with TBI when in hospital and at six months after discharge.

MATERIALS AND METHODS

All patients attended our emergency department during July 2014 and December 2015 and were consecutively entered into the study and among 890 evaluated candidates based on inclusion criteria we finally investigated the serum UA levels of 725 TBI patients. Computed Tomography (CT) images of the brain were obtained within the first 24 hours of hospitalization. Outcome was assessed using the Glasgow Outcome Scale (GOS) score at discharge and at six months after discharge.

RESULTS

Data of 725 patients (42.89% men; mean age: 54.69±12.37 years) were analyzed. Mean±Standard Deviation (SD) of Glasgow Coma Scale (GCS) scores was 4.65±1.76. Serum levels of UA, when in hospital and at six months after discharge, among those who died were lower than those who survived (in hospital: 0.126±0.026 vs. 0.243±0.942 mmol/l, p = 0.000; 6 months post-discharge: 0.130±0.044 vs. 0.286±0.069 mmol/l, p<0.001). The mean UA plasma was significantly different between deceased and alive patients according to GOS scores (p<0.001 and p=0.030, respectively). The UA levels showed a significant relationship with GCS scores and severity of brain injury assessed using the Marshall Classification Score (p=0.005).

CONCLUSION

Our results showed a strong relationship between UA levels and patients' outcomes either in hospital or at six months after discharge. Serum UA level could be considered as a valuable marker for evaluating the severity of brain injury and outcomes of TBI.

Past, Present, and Future of Traumatic Brain Injury Research

Traumatic brain injury (TBI) is the greatest cause of death and severe disability in young adults; its incidence is increasing in the elderly and in the developing world. Outcome from severe TBI has improved dramatically as a result of advancements in trauma systems and supportive critical care, however we remain without a therapeutic which acts directly to attenuate brain injury. Recognition of secondary injury and its molecular mediators has raised hopes for such targeted treatments. Unfortunately, over 30 late-phase clinical trials investigating promising agents have failed to translate a therapeutic for clinical use. Numerous explanations for this failure have been postulated and are reviewed here. With this historical context we review ongoing research and anticipated future trends which are armed with lessons from past trials, new scientific advances, as well as improved research infrastructure and funding. There is great hope that these new efforts will finally lead to an effective therapeutic for TBI as well as better clinical management strategies.

The Glasgow Outcome Scale - 40 years of application and refinement

The Glasgow Outcome Scale (GOS) was first published in 1975 by Bryan Jennett and Michael Bond. With over 4,000 citations to the original paper, it is the most highly cited outcome measure in studies of brain injury and the second most-cited paper in clinical neurosurgery. The original GOS and the subsequently developed extended GOS (GOSE) are recommended by several national bodies as the outcome measure for major trauma and for head injury. The enduring appeal of the GOS is linked to its simplicity, short administration time, reliability and validity, stability, flexibility of administration (face-to-face, over the telephone and by post), cost-free availability and ease of access. These benefits apply to other derivatives of the scale, including the Glasgow Outcome at Discharge Scale (GODS) and the GOS paediatric revision. The GOS was devised to provide an overview of outcome and to focus on social recovery. Since the initial development of the GOS, there has been an increasing focus on the multidimensional nature of outcome after head injury. This Review charts the development of the GOS, its refinement and usage over the past 40 years, and considers its current and future roles in developing an understanding of brain injury.

Role of α-II-spectrin breakdown products in the prediction of the severity and clinical outcome of acute traumatic brain injury

αII-spectrin breakdown products are regarded as potential biomarkers for traumatic brain injury (TBI). The aim of the present study was to further evaluate these biomarkers by assessing their clinical utility in predicting the severity of injury and clinical outcome of patients with TBI. Eligible patients with acute TBI (n=17), defined by a Glasgow Coma Scale (GCS) score of ≤8, were enrolled. Ventricular cerebrospinal fluid (CSF) was sampled from each patient at 24, 72 and 120 h following TBI. An immunoblot assay was used to determine the concentrations of SBDPs in the CSF samples. The concentrations of SBDPs combined with the GCS score at 24 h after injury and the Glasgow Outcome Score (GOS) at 30 days after injury were compared and analyzed. The levels of SBDPs in CSF were markedly increased following acute TBI in comparison with those in the control group. In the early period after TBI, the levels of SBDPs were closely associated with GCS score. Comparisons of the SBDP levels with the severity of injury revealed significant differences between patients with the most severe brain injury and patients with severe brain injury in the first 24 h post-injury (P<0.05). The levels and dynamic changes of SBDPs in CSF exhibited a close association with GOS at 30 days after injury. The levels of SBDPs differed significantly between patients grouped according to prognosis (P<0.05). These results suggest that in the early period after TBI, the levels and dynamic changes of SBDPs in CSF can be useful in the prediction of the severity of injury and clinical outcome of patients.

Computed Tomography and Shifts to Alternate Imaging Modalities in Hospitalized Children

BACKGROUND

Many studies have demonstrated a rise in computed tomography (CT) utilization in abstract children's hospitals. However, CT utilization may be declining, perhaps due to awareness of potential hazards of pediatric ionizing radiation, such as increased risk of malignancy. Th e objective is to assess the trend in CT utilization in hospitalized children at freestanding children's hospitals from 2004 to 2012 and we hypothesize decreases are associated with shifts to alternate imaging modalities.

METHODS

Multicenter cross-sectional study of children admitted to 33 pediatric tertiary-care hospitals participating in the Pediatric Health Information System between January 1, 2004, and December 31, 2012. The rates of CT, ultrasound, and MRI for the top 10 All-Patient Refined Diagnosis Related Groups (APR-DRGs) for which CT was performed in 2004 were determined by billing data. Rates of each imaging modality for those top 10 APR-DRGs were followed through the study period. Odds ratios of imaging were adjusted for demographics and illness severity.

RESULTS

For all included APR-DRGs except ventricular shunt procedures and nonbacterial gastroenteritis, the number of children imaged with any modality increased. CT utilization decreased for all APR-DRGs (P values , .001). For each of the APR-DRGs except seizure and infections of upper respiratory tract, the decrease in CT was associated with a significant rise in an alternative imaging modality (P values # .005).

CONCLUSIONS

For the 10 most common APR-DRGs for which children received CT in 2004,a decrease in CT utilization was found in 2012. Alternative imaging modalities for 8 of the diagnoses were used.

Design of acute neuroprotection studies

Traumatic brain injury (TBI) is a substantial public health problem. The discovery of progressive, ongoing damage to the brain by means of complex molecular mechanisms which follow the initial injury has raised the possibility of targeted therapeutic intervention. Despite a substantial investment in trials testing dozens of therapeutics in humans, however, to date none has demonstrated robust efficacy. Deficiencies in the design of human clinical trials is likely to explain many translational failures, at least in part. Here we review secondary injury mediators and key trials which have targeted them. We provide a thorough discussion of putative reasons why trials thus far have failed and suggestions for the design of future clinical studies. Important insights from the IMPACT study are also presented in detail; in addition to providing critical insights for future trial design and analysis it suggests that reanalysis of completed studies may reveal inappropriately discarded treatments. Unfortunately limited resources are available for translational research and it is difficult to procure funds needed for well-resourced, large and definitive studies. History suggests, however, that investing in studies that are unlikely to provide a definitive answer only serves to increase required investment as they tend to mandate further study.

Optimising outcome assessment to improve quality and efficiency of stroke trials

Substantial progress has been made in treatment of stroke and much of this has been driven by large scale, multi-centre, randomised controlled trials. Although stroke is a frequent cause of mortality, stroke-related disability and functional decline is of equal or greater concern to patients and carers. Thus, to prove efficacy of an intervention for stroke, we need robust methods of describing recovery. Various functional assessment scales are available, the tool recommended as trial end point by many specialist societies and regulatory authorities is the modified Rankin Scale (mRS). We will use the mRS as exemplar to discuss contemporary research around functional assessment for stroke trials, including recent work around structured assessments, assessor training and end point adjudication panels. We will present an overview and critique of these studies and give examples where strategies to improve mRS assessment are impacting on the quality of stroke clinical trials.

The Glasgow Outcome at Discharge Scale: an inpatient assessment of disability after brain injury

This study assesses the validity and reliability of the Glasgow Outcome at Discharge Scale (GODS), which is a tool that is designed to assess disability after brain injury in an inpatient setting. It is derived from the Glasgow Outcome Scale-Extended (GOS-E), which assesses disability in the community after brain injury. Inter-rater reliability on the GODS is high (quadratic-weighted kappa 0.982; 95% confidence interval [CI] 0.968, 0.996) as is concurrent validity with the Disability Rating Scale (DRS) (Spearman correlation -0.728; 95% CI -0.819, -0.601). The GODS is significantly associated with physical and fatigue subscales of the short form (SF)-36 in hospital. In terms of predictive validity the GODS is highly associated with the GOS-E after discharge (Spearman correlation 0.512; 95% CI 0.281, 0.687), with the DRS, and with physical, fatigue, and social subscales of the SF-36. The GODS is recommended as an assessment tool for disability after brain injury pre-discharge and can be used in conjunction with the GOS-E to monitor disability between hospital and the community.

Defining glaucomatous optic neuropathy from a continuous measure of optic nerve damage - the optimal cut-off point for risk-factor analysis in population-based epidemiology

PURPOSE

Diseases characterized by a continuous trait can be defined by setting a cut-off point for the disease measure in question, accepting some misclassification. The 97.5th percentile is commonly used as a cut-off point. However, it is unclear whether this percentile is the optimal cut-off point from the point of view of risk-factor analysis. The optimal cut-off point for risk-factor analysis can be found with a statistical method that minimizes the effect of misclassification. We applied this method to glaucomatous optic neuropathy. Here, the continuous trait is the cup-disc ratio. The aim of this study was to determine the optimal cup-disc ratio cut-off point for risk-factor analysis in population-based epidemiology.

METHODS

All participants in the population-based Rotterdam Study underwent intraocular pressure (IOP) measurements, assessment of the cup-disc ratio with the Heidelberg Retina Tomograph (HRT) and visual field testing. In the statistical method, the cup-disc ratio (the continuous trait) and the IOP (a major risk factor) were independent variables and glaucomatous visual field loss (the true glaucoma endpoint) the dependent variable in a logistic regression model. The optimal cup-disc ratio cut-off point was found by minimizing the influence of IOP in this model. Variability of the approach was assessed by using a bootstrap resampling technique.

RESULTS

Of 2444 included participants, 93 had glaucomatous visual field loss. The median optimal cup-disc ratio cut-off point was the 97.0th percentile with a 95% central range from 95.5 to 98.5.

CONCLUSION

The optimal cup-disc ratio cut-off point for risk-factor analysis is close to the commonly used 97.5th percentile.

Antihypertensive Treatment of Acute Cerebral Hemorrhage (ATACH) II: design, methods, and rationale

The December 2003 report from the National Institute of Neurological Disorders and Stroke (NINDS) Workshop on priorities for clinical research in intracerebral hemorrhage (ICH) recommended clinical trials for evaluation of blood pressure management in acute ICH as a leading priority. The Special Writing Group of the Stroke Council of the American Heart Association in 1999 and 2007 emphasized the need for clinical trials to ensure evidence-based treatment of acute hypertensive response in ICH. To address important gaps in knowledge, we conducted a pilot study funded by the NINDS, Antihypertensive Treatment of Acute Cerebral Hemorrhage (ATACH) I Trial, during 2004-2008 to determine the appropriate level of systolic blood pressure (SBP) reduction. We now have initiated a multi-center, randomized Phase III trial, the ATACH II Trial, to definitively determine the efficacy of early, intensive, antihypertensive treatment using intravenous (IV) nicardipine initiated within 3 h of onset of ICH and continued for the next 24 h in subjects with spontaneous supratentorial ICH. The primary hypothesis of this large (N = 1,280), streamlined, and focused trial is that SBP reduction to ≤140 mm Hg reduces the likelihood of death or disability at 3 months after ICH, defined by modified Rankin scale score of 4-6, by at least 10% absolute compared to standard SBP reduction to ≤180 mm Hg. The ATACH II trial is a natural extension of numerous case series, the subsequent ATACH I pilot trial, and a preliminary, randomized, and controlled trial in this patient population funded by the Australian National Health and Medical Research Council. Both trials recently confirmed the safety and tolerability of both the regimen and goals of antihypertensive treatment in acutely hypertensive patients with ICH, as proposed in the present trial. The underlying mechanism for this expected beneficial effect of intensive treatment is presumably mediated through reduction of the rate and magnitude of hematoma expansion observed in approximately 73% of the patients with acute ICH. The Australian trial provided preliminary evidence of attenuation of hematoma expansion with intensive SBP reduction. The ATACH II trial will have important public health implications by providing evidence of, or lack thereof, regarding the efficacy and safety of acute antihypertensive treatment in subjects with ICH. This treatment represents a strategy that can be made widely available without the need for specialized equipment and personnel, and therefore, can make a major impact upon clinical practice for treating patients with ICH.

Neuronal and glial markers are differently associated with computed tomography findings and outcome in patients with severe traumatic brain injury: a case control study

INTRODUCTION

Authors of several studies have studied biomarkers and computed tomography (CT) findings in the acute phase after severe traumatic brain injury (TBI). However, the correlation between structural damage as assessed by neuroimaging and biomarkers has not been elucidated. The aim of this study was to investigate the relationships among neuronal (Ubiquitin carboxy-terminal hydrolase L1 [UCH-L1]) and glial (glial fibrillary acidic protein [GFAP]) biomarker levels in serum, neuroradiological findings and outcomes after severe TBI.

METHODS

The study recruited patients from four neurotrauma centers. Serum samples for UCH-L1 and GFAP were obtained at the time of hospital admission and every 6 hours thereafter. CT scans of the brain were obtained within 24hrs of injury. Outcome was assessed by Glasgow Outcome Scale (GOS) at discharge and at 6 months.

RESULTS

81 severe TBI patients and 167 controls were enrolled. The mean serum levels of UCH-L1 and GFAP were higher (p < 0.001) in TBI patients compared to controls. UCH-L1 and GFAP serum levels correlated significantly with Glasgow Coma Scale (GCS) and CT findings. GFAP levels were higher in patients with mass lesions than in those with diffuse injury (2.95 ± 0.48 ng/ml versus 0.74 ± 0.11 ng/ml) while UCH-L1 levels were higher in patients with diffuse injury (1.55 ± 0.18 ng/ml versus 1.21 ± 0.15 ng/ml, p = 0.0031 and 0.0103, respectively). A multivariate logistic regression showed that UCH-L1 was the only independent predictor of death at discharge [adjusted odds ratios 2.95; 95% confidence interval, 1.46-5.97], but both UCH-L1 and GFAP levels strongly predicted death 6 months post-injury.

CONCLUSIONS

Relationships between structural changes detected by neuroimaging and biomarkers indicate each biomarker may reflect a different injury pathway. These results suggest that protein biomarkers could provide better characterization of subjects at risk for specific types of cellular damage than that obtained with neuroimaging alone, as well as provide valuable information about injury severity and outcome after severe TBI.

Measuring outcome in traumatic brain injury treatment trials: recommendations from the traumatic brain injury clinical trials network

BACKGROUND

Traumatic brain injury (TBI) involves several aspects of a patient's condition, including physical, mental, emotional, cognitive, social, and functional changes. Therefore, a clinical trial with individuals with TBI should consider outcome measures that reflect their global status.

METHODS

We present the work of the National Institute of Child Health and Development-sponsored Traumatic Brain Injury Clinical Trials Network Outcome Measures subcommittee and its choice of outcome measures for a phase III clinical trial of patients with complicated mild to severe TBI.

RESULTS

On the basis of theoretical and practical considerations, the subcommittee recommended the adoption of a core of 9 measures that cover 2 different areas of recovery: functional and cognitive. These measures are the Extended Glasgow Outcome Scale; the Controlled Oral Word Association Test; the Trail Making Test, Parts A and B; the California Verbal Learning Test-II; the Wechsler Adult Intelligence Scale-III Digit Span subtest; the Wechsler Adult Intelligence Scale-III Processing Speed Index; and the Stroop Color-Word Matching Test, Parts 1 and 2.

CONCLUSIONS

The statistical methods proposed to analyze these measures using a global test procedure, along with research and methodological and regulatory issues involved with the use of multiple outcomes in a clinical trial, are discussed.

A method for reducing misclassification in the extended Glasgow Outcome Score

The eight-point extended Glasgow Outcome Scale (GOSE) is commonly used as the primary outcome measure in traumatic brain injury (TBI) clinical trials. The outcome is conventionally collected through a structured interview with the patient alone or together with a caretaker. Despite the fact that using the structured interview questionnaires helps reach agreement in GOSE assessment between raters, significant variation remains among different raters. We introduce an alternate GOSE rating system as an aid in determining GOSE scores, with the objective of reducing inter-rater variation in the primary outcome assessment in TBI trials. Forty-five trauma centers were randomly assigned to three groups to assess GOSE scores on sample cases, using the alternative GOSE rating system coupled with central quality control (Group 1), the alternative system alone (Group 2), or conventional structured interviews (Group 3). The inter-rater variation between an expert and untrained raters was assessed for each group and reported through raw agreement and with weighted kappa (kappa) statistics. Groups 2 and 3 without central review yielded inter-rater agreements of 83% (weighted kappa = 0.81; 95% CI 0.69, 0.92) and 83% (weighted kappa = 0.76, 95% CI 0.63, 0.89), respectively, in GOS scores. In GOSE, the groups had an agreement of 76% (weighted kappa = 0.79; 95% CI 0.69, 0.89), and 63% (weighted kappa = 0.70; 95% CI 0.60, 0.81), respectively. The group using the alternative rating system coupled with central monitoring yielded the highest inter-rater agreement among the three groups in rating GOS (97%; weighted kappa = 0.95; 95% CI 0.89, 1.00), and GOSE (97%; weighted kappa = 0.97; 95% CI 0.91, 1.00). The alternate system is an improved GOSE rating method that reduces inter-rater variations and provides for the first time, source documentation and structured narratives that allow a thorough central review of information. The data suggest that a collective effort can be made to minimize inter-rater variation.

The Causative Classification of Stroke system: an international reliability and optimization study

BACKGROUND

Valid and reliable ischemic stroke subtype determination is crucial for well-powered multicenter studies. The Causative Classification of Stroke System (CCS, available at http://ccs.mgh.harvard.edu) is a computerized, evidence-based algorithm that provides both causative and phenotypic stroke subtypes in a rule-based manner. We determined whether CCS demonstrates high interrater reliability in order to be useful for international multicenter studies.

METHODS

Twenty members of the International Stroke Genetics Consortium from 13 centers in 8 countries, who were not involved in the design and development of the CCS, independently assessed the same 50 consecutive patients with acute ischemic stroke through reviews of abstracted case summaries. Agreement among ratings was measured by kappa statistic.

RESULTS

The κ value for causative classification was 0.80 (95% confidence interval [CI] 0.78-0.81) for the 5-subtype, 0.79 (95% CI 0.77-0.80) for the 8-subtype, and 0.70 (95% CI 0.69-0.71) for the 16-subtype CCS. Correction of a software-related factor that generated ambiguity improved agreement: κ = 0.81 (95% CI 0.79-0.82) for the 5-subtype, 0.79 (95% CI 0.77-0.80) for the 8-subtype, and 0.79 (95% CI 0.78-0.80) for the 16-subtype CCS. The κ value for phenotypic classification was 0.79 (95% CI 0.77-0.82) for supra-aortic large artery atherosclerosis, 0.95 (95% CI 0.93-0.98) for cardioembolism, 0.88 (95% CI 0.85-0.91) for small artery occlusion, and 0.79 (0.76-0.82) for other uncommon causes.

CONCLUSIONS

CCS allows classification of stroke subtypes by multiple investigators with high reliability, supporting its potential for improving stroke classification in multicenter studies and ensuring accurate means of communication among different researchers, institutions, and eras.

Advances in the diagnosis of etiologic subtypes of ischemic stroke

A fundamental goal of etiologic stroke classification is to generate subgroups with discrete phenotypic, therapeutic, and prognostic features. Accurate stroke classification requires integration of multiple aspects of diagnostic stroke evaluation in a standardized manner. Diagnostic test findings can be simply organized into major etiologic groups to create a phenotypic subtype, or they can be reduced to a single causative subtype through a decision-making process. It is essential for a classification system to provide consistent results across different raters in different clinical settings. Comparability of subtype assignments is the key to valid communication of research results across the field. This article highlights important theoretical aspects of etiologic stroke classification and reviews major etiologic classification systems that have benefited from recent advances in etiologic stroke evaluation.

Ubiquitin C-terminal hydrolase is a novel biomarker in humans for severe traumatic brain injury

OBJECTIVE

Ubiquitin C-terminal hydrolase (UCH-L1), also called neuronal-specific protein gene product (PGP 9.3), is highly abundant in neurons. To assess the reliability of UCH-L1 as a potential biomarker for traumatic brain injury (TBI) this study compared cerebrospinal fluid (CSF) levels of UCH-L1 from adult patients with severe TBI to uninjured controls; and examined the relationship between levels with severity of injury, complications and functional outcome.

DESIGN

This study was designed as prospective case control study.

PATIENTS

This study enrolled 66 patients, 41 with severe TBI, defined by a Glasgow coma scale (GCS) score of < or =8, who underwent intraventricular intracranial pressure monitoring and 25 controls without TBI requiring CSF drainage for other medical reasons.

SETTING

: Two hospital system level I trauma centers.

MEASUREMENTS AND MAIN RESULTS

Ventricular CSF was sampled from each patient at 6, 12, 24, 48, 72, 96, 120, 144, and 168 hrs following TBI and analyzed for UCH-L1. Injury severity was assessed by the GCS score, Marshall Classification on computed tomography and a complicated postinjury course. Mortality was assessed at 6 wks and long-term outcome was assessed using the Glasgow outcome score 6 months after injury. TBI patients had significantly elevated CSF levels of UCH-L1 at each time point after injury compared to uninjured controls. Overall mean levels of UCH-L1 in TBI patients was 44.2 ng/mL (+/-7.9) compared with 2.7 ng/mL (+/-0.7) in controls (p <.001). There were significantly higher levels of UCH-L1 in patients with a lower GCS score at 24 hrs, in those with postinjury complications, in those with 6-wk mortality, and in those with a poor 6-month dichotomized Glasgow outcome score.

CONCLUSIONS

These data suggest that this novel biomarker has the potential to determine injury severity in TBI patients. Further studies are needed to validate these findings in a larger sample.

IMPACT recommendations for improving the design and analysis of clinical trials in moderate to severe traumatic brain injury

Clinical trials in traumatic brain injury (TBI) pose complex methodological challenges, largely related to the heterogeneity of the population. The International Mission on Prognosis and Clinical Trial Design in TBI study group has explored approaches for dealing with this heterogeneity with the aim to optimize clinical trials in TBI. Extensive prognostic analyses and simulation studies were conducted on individual patient data from eight trials and three observational studies. Here, we integrate the results of these studies into the International Mission on Prognosis and Clinical Trial Design in TBI recommendations for design and analysis of trials in TBI: Details of the major baseline prognostic characteristics should be provided in every report on a TBI study; in trials they should be differentiated per treatment group. We also advocate the reporting of the baseline prognostic risk as determined by validated prognostic models. Inclusion criteria should be as broad as is compatible with the current understanding of the mechanisms of action of the intervention being evaluated. This will maximize recruitment rates and enhance the generalizability of the results. The statistical analysis should incorporate prespecified covariate adjustment to mitigate the effects of the heterogeneity. The statistical analysis should use an ordinal approach, based on either sliding dichotomy or proportional odds methodology. Broad inclusion criteria, prespecified covariate adjustment, and an ordinal analysis will promote an efficient trial, yielding gains in statistical efficiency of more than 40%. This corresponds to being able to detect a 7% treatment effect with the same number of patients needed to demonstrate a 10% difference with an unadjusted analysis based on the dichotomized Glasgow outcome scale.

Effects of Glasgow Outcome Scale misclassification on traumatic brain injury clinical trials

The Glasgow Outcome Scale (GOS) is the primary endpoint for efficacy analysis of clinical trials in traumatic brain injury (TBI). Accurate and consistent assessment of outcome after TBI is essential to the evaluation of treatment results, particularly in the context of multicenter studies and trials. The inconsistent measurement or interobserver variation on GOS outcome, or for that matter, on any outcome scales, may adversely affect the sensitivity to detect treatment effects in clinical trial. The objective of this study is to examine effects of nondifferential misclassification of the widely used five-category GOS outcome scale and in particular to assess the impact of this misclassification on detecting a treatment effect and statistical power. We followed two approaches. First, outcome differences were analyzed before and after correction for misclassification using a dataset of 860 patients with severe brain injury randomly sampled from two TBI trials with known differences in outcome. Second, the effects of misclassification on outcome distribution and statistical power were analyzed in simulation studies on a hypothetical 800-patient dataset. Three potential patterns of nondifferential misclassification (random, upward and downward) on the dichotomous GOS outcome were analyzed, and the power of finding treatments differences was investigated in detail. All three patterns of misclassification reduce the power of detecting the true treatment effect and therefore lead to a reduced estimation of the true efficacy. The magnitude of such influence not only depends on the size of the misclassification, but also on the magnitude of the treatment effect. In conclusion, nondifferential misclassification directly reduces the power of finding the true treatment effect. An awareness of this procedural error and methods to reduce misclassification should be incorporated in TBI clinical trials.

Variability in modified Rankin scoring across a large cohort of international observers

BACKGROUND AND PURPOSE

The modified Rankin scale (mRS) is the most commonly used outcome measure in stroke trials. However, substantial interobserver variability in mRS scoring has been reported. These studies likely underestimate the variability present in multicenter clinical trials, because exploratory work has only been undertaken in single centers by a few observers, all of similar training. We examined mRS variability across a large cohort of international observers using data from a video training resource.

METHODS

The mRS training package includes a series of "real-life" patient interviews for grading. Training data were collected centrally and analyzed for variability using kappa statistics. We examined variability against a standard of "correct" mRS grades; examined variability by country; and for UK assessors, examined variability by center and by professional background of the observer.

RESULTS

To date, 2942 assessments from 30 countries have been submitted. Overall reliability for mRS grading has been moderate to good with substantial heterogeneity across countries. Native English language has had little effect on reliability. Within the United Kingdom, there was no significant variation by profession.

CONCLUSIONS

Our results confirm interobserver variability in mRS assessment. The heterogeneity across countries is intriguing because it appears not to be related solely to language. These data highlight the need for novel strategies to improve reliability.

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.

Initial Experience of a Digital Training Resource for Modified Rankin Scale Assessment in Clinical Trials

BACKGROUND AND PURPOSE

The modified Rankin Scale (mRS) is the preferred measure of disability in cerebrovascular clinical trials, but its value is restricted by interobserver variability. Poor reliability reduces the statistical power of clinical trials and leads to underestimation of effect size. Strategies to improve mRS grading are required. Video training has previously improved application of the National Institutes of Health Stroke Scale in clinical research. We developed an mRS training resource in an attempt to minimize interobserver variability.

METHODS

We produced a complete training resource comprising an instructional DVD with accompanying written materials and assessment recordings of patient interviews. Formal assessment of training involved grading of real-life cases. Results of initial training and recertification were collected centrally and scored.

RESULTS

Data from 1564 assessments are presented. The majority of assessors were participating in 2 large prospective clinical stroke trials. Assessors represented a mixed group of disciplines and nationalities. After training, most trainees (90%) achieved certification in mRS assessment. The majority (85%) of investigators who did not reach an acceptable score on initial testing achieved certification after further exposure to the package.

CONCLUSIONS

Mass training in mRS assessment for clinical trials is possible. We outline the development of a video-based training package, including technical issues, patient selection procedures, and methods of scoring and assessment. Certification results suggest that use of the resource can improve mRS grading. Acceptability of the training has been demonstrated by its successful use in 2 international acute stroke trials, SAINT 1 and CHANT.

Clinical significance of alphaII-spectrin breakdown products in cerebrospinal fluid after severe traumatic brain injury

Following traumatic brain injury (TBI), the cytoskeletal protein alpha-II-spectrin is proteolyzed by calpain and caspase-3 to signature breakdown products. To determine whether alpha -II-spectrin proteolysis is a potentially reliable biomarker for TBI in humans, the present study (1) examined levels of spectrin breakdown products (SBDPs) in cerebrospinal fluid (CSF) from adults with severe TBI and (2) examined the relationship between these levels, severity of injury, and clinical outcome. This prospective case control study enrolled 41 patients with severe TBI, defined by a Glasgow Coma Scale (GCS) score of < or =8, who underwent intraventricular intracranial pressure monitoring. Patients without TBI requiring CSF drainage for other medical reasons served as controls. Ventricular CSF was sampled from each patient at 6, 12, 24, 48, 72, 96, and 120 h following TBI and analyzed for SBDPs. Outcome was assessed using the Glasgow Outcome Score (GOS) 6 months after injury. Calpain and caspase-3 mediated SBDP levels in CSF were significantly increased in TBI patients at several time points after injury, compared to control subjects. The time course of calpain mediated SBDP150 and SBDP145 differed from that of caspase-3 mediated SBDP120 during the post-injury period examined. Mean SBDP densitometry values measured early after injury correlated with severity of injury, computed tomography (CT) scan findings, and outcome at 6 months post-injury. Taken together, these results support that alpha -II-spectrin breakdown products are potentially useful biomarker of severe TBI in humans. Our data further suggests that both necrotic/oncotic and apoptotic cell death mechanisms are activated in humans following severe TBI, but with a different time course after injury.

Adjustment for Strong Predictors of Outcome in Traumatic Brain Injury Trials: 25% Reduction in Sample Size Requirements in the IMPACT Study

The aim of this study was to quantify the potential reduction in sample size that can be achieved by adjustment for predictors of outcome in traumatic brain injury (TBI) trials. We used individual patient data from seven therapeutic phase III randomized clinical trials (RCTs; n = 6166) in moderate or severe TBI, and three TBI surveys (n = 2238). The primary outcome was the dichotomized Glasgow Outcome Scale at 6 months (favorable/unfavorable). Baseline predictors of outcome considered were age, motor score, pupillary reactivity, computed tomography (CT) classification, traumatic subarachnoid hemorrhage, hypoxia, hypotension, glycemia, and hemoglobin. We calculated the potential sample size reduction obtained by adjustment of a hypothetical treatment effect for one to seven predictors with logistic regression models. The distribution of predictors was more heterogeneous in surveys than in trials. Adjustment of the treatment effect for the strongest predictors (age, motor score, and pupillary reactivity) yielded a reduction in sample size of 16-23% in RCTs and 28-35% in surveys. Adjustment for seven predictors yielded a reduction of about 25% in most studies: 20-28% in RCTs and 32-39% in surveys. A major reduction in sample size can be obtained with covariate adjustment in TBI trials. Covariate adjustment for strong predictors should be incorporated in the analysis of future TBI trials.

Subgroup analysis and covariate adjustment in randomized clinical trials of traumatic brain injury: a systematic review

OBJECTIVE

Few randomized clinical trials (RCTs) in the field of traumatic brain injury (TBI) have shown a significant treatment benefit. We critically reviewed the use of two types of secondary analyses, covariate adjustment and subgroup analysis, which are common in TBI trials.

METHODS

We performed a systematic review of therapeutic phase III RCTs, including adult patients with acute, moderate-to-severe TBI. Glasgow Outcome Scale (GOS) at > or =3 months as outcome, and > or =50 patients per arm were required. We compared the actual reporting of covariate adjustment and subgroup analyses with the Consolidated Standards of Reporting Trials (CONSORT) recommendations. Likewise, we reviewed six protocols of large multicenter RCTs and compared planned and reported subgroups.

RESULTS

We identified 18 RCTs (n = 6439). Sixteen trials used GOS at 6 months as outcome. Five RCTs reported covariate adjustment. The number of covariates was limited (< or =5), most frequently including age. Many covariates were outcome predictors. Four RCTs reported only adjusted treatment effects as the main efficacy parameter. Eleven RCTs reported subgroup analyses. Several subgroup factors (< or =7, mainly outcome predictors) and outcomes (< or =4) were included. The highest total number of subgroups was 15, and only three RCTs completely pre-specified subgroups. Notably, 10 of 11 RCTs performed inappropriate separate subgroup analyses. Of 11 RCTs, 5 gave subgroups the same emphasis as the overall effect. Reported subgroup analyses were insufficiently described and clearly differed from those planned in the protocol.

CONCLUSION

The reported covariate adjustment and subgroup analyses from TBI trials had several methodological shortcomings. Appropriate performance and reporting of covariate adjustment and subgroup analysis should be considerably improved in future TBI trials because interpretation of treatment benefits may be misleading otherwise.

Reliability of the modified Rankin Scale across multiple raters: benefits of a structured interview

BACKGROUND AND PURPOSE

The modified Rankin Scale (mRS) is widely used to assess global outcome after stroke. The aim of the study was to examine rater variability in assessing functional outcomes using the conventional mRS, and to investigate whether use of a structured interview (mRS-SI) reduced this variability.

METHODS

Inter-rater agreement was studied among raters from 3 stroke centers. Fifteen raters were recruited who were experienced in stroke care but came from a variety of professional backgrounds. Patients at least 6 months after stroke were first assessed using conventional mRS definitions. After completion of initial mRS assessments, raters underwent training in the use of a structured interview, and patients were re-assessed. In a separate component of the study, intrarater variability was studied using 2 raters who performed repeat assessments using the mRS and the mRS-SI. The design of the latter part of the study also allowed investigation of possible improvement in rater agreement caused by repetition of the assessments. Agreement was measured using the kappa statistic (unweighted and weighted using quadratic weights).

RESULTS

Inter-rater reliability: Pairs of raters assessed a total of 113 patients on the mRS and mRS-SI. For the mRS, overall agreement between raters was 43% (kappa=0.25, kappa(w)=0.71), and for the structured interview overall agreement was 81% (kappa=0.74, kappa(w)=0.91). Agreement between raters was significantly greater on the mRS-SI than the mRS (P<0.001). Intrarater reliability: Repeatability of both the mRS and mRS-SI was excellent (kappa=0.81, kappa(w) > or =0.94).

CONCLUSIONS

Although individual raters are consistent in their use of the mRS, inter-rater variability is nonetheless substantial. Rater variability on the mRS is thus particularly problematic for studies involving multiple raters. There was no evidence that improvement in inter-rater agreement occurred simply with repetition of the assessment. Use of a structured interview improves agreement between raters in the assessment of global outcome after stroke.

Improving the assessment of outcomes in stroke: use of a structured interview to assign grades on the modified Rankin Scale

BACKGROUND AND PURPOSE

The modified Rankin Scale is widely used to assess changes in activity and lifestyle after stroke, but it has been criticized for its subjectivity. The purpose of the present study was to compare conventional assessment on the modified Rankin Scale with assessment through a structured interview.

METHODS

Sixty-three patients with stroke 6 to 24 months previously were interviewed and graded independently on the modified Rankin Scale by 2 observers. These observers then underwent training in use of a structured interview for the scale that covered 5 areas of everyday function. Eight weeks after the first assessment, the same observers reassessed 58 of these patients using the structured interview.

RESULTS

Interrater reliability was measured with the kappa statistic (weighted with quadratic weights). For the scale applied conventionally, overall agreement between the 2 raters was 57% (kappa(w)=0.78); 1 rater assigned significantly lower grades than the other (P=0.048). On the structured interview, the overall agreement between raters was 78% (kappa(w)=0.93), and there was no overall difference between raters in grades assigned (P=0.17). Rankin grades from the conventional assessment and the structured interview were highly correlated, but there was significantly less disagreement between raters when the structured interview was used (P=0.004).

CONCLUSIONS

Variability and bias between raters in assigning patients to Rankin grades may be reduced by use of a structured interview. Use of a structured interview for the scale could potentially improve the quality of results from clinical studies in stroke.

Reliability of postal questionnaires for the Glasgow Outcome Scale

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.