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Table of Contents    
ORIGINAL ARTICLE
Year : 2017  |  Volume : 65  |  Issue : 1  |  Page : 83-86

Predictive validity of disability rating scale in determining functional outcome in patients with severe traumatic brain injury


1 Department of Clinical Neurosciences, National Institute of Mental Health and Neurosciences, Bengaluru, Karnataka, India
2 Department of Neurosurgery, National Institute of Mental Health and Neurosciences, Bengaluru, Karnataka, India

Date of Web Publication12-Jan-2017

Correspondence Address:
Dhaval Shukla
Department of Neurosurgery, National Institute of Mental Health and Neurosciences, Bengaluru - 560 029, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.198228

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 » Abstract 

Background: Most patients with severe traumatic brain injury (TBI) are discharged when they have still not recovered completely. Many such patients are not available for follow up.
Aims: We conducted this study to determine whether the condition at discharge from acute care setting, as assessed with disability rating scale (DRS), correlates with functional outcome at follow up.
Settings and Design: This study was conducted at a Neurosurgical intensive care unit (ICU) of a tertiary care referral center. This was a prospective observational study.
Materials and Methods: Patients admitted to ICU with a diagnosis of severe TBI were enrolled for the study. On the day of discharge, all patients underwent DRS assessment. A final assessment was performed using Glasgow outcome scale extended (GOSE) at 6 months after discharge from the hospital.
Statistical Analysis: The correlation between the DRS scores at the time of discharge with DRS scores and GOSE categories at 6 months after discharge was determined using Spearman's rho correlation coefficient.
Results: A total of 88 patients were recruited for the study. The correlation coefficient of DRS at discharge for DRS at 6 months was 0.536 and for GOSE was −0.553. The area under the curve of DRS score at discharge for predicting unfavorable outcome and mortality at 6 months was 0.770 and 0.820, respectively.
Conclusion: The predictive validity of DRS is fair to good in determining GOSE at follow-up. Pending availability of a more accurate outcome assessment tool, DRS at discharge can be used as a surrogate outcome for GOSE at follow up.


Keywords: Disability rating scale, Glasgow outcome scale extended, traumatic brain injury
Key Messages:
Disability rating scale at discharge has a good predicitive validity in determining the Glasgow outcome scale extended at follow up visits in patients with severe traumatic brain injury who have undergone treatment in a neurosurgical intensive care unit.


How to cite this article:
Deepika A, Devi B I, Shukla D. Predictive validity of disability rating scale in determining functional outcome in patients with severe traumatic brain injury. Neurol India 2017;65:83-6

How to cite this URL:
Deepika A, Devi B I, Shukla D. Predictive validity of disability rating scale in determining functional outcome in patients with severe traumatic brain injury. Neurol India [serial online] 2017 [cited 2017 Sep 22];65:83-6. Available from: http://www.neurologyindia.com/text.asp?2017/65/1/83/198228


Most patients with severe traumatic brain injury (TBI) are discharged when they have still not recovered completely without assessment of their need for rehabilitation or of appropriate referral. Many such patients are not available for follow up, and it is difficult to gather information of the outcome of these patients. An assessment of disability at the time of discharge with a simple and robust measure administrable by non-specialist ward staff would be useful in addressing these issues. An association of disability at the time of discharge with subsequent functioning in the community at follow-up would also make pre-discharge assessment as a predictor of later outcome. In research concerning acute care, it may act as a “surrogate” early end-point that may, to an extent, compensate for loss to follow up. At present, many researchers use in-hospital mortality as the only outcome measure in acute care settings. Some researchers also use Glasgow coma scale (GCS) as an outcome measure to assess for the effect of intervention in acute settings. Even Glasgow Outcome Scale (GOS) has been used to assess outcome at the time of discharge. The GOS is a functional outcome measure, and should not be used in the inpatient setting.[1] Despite this, the GOS continues to be inappropriately used in studies on hospitalized patients. Although a variety of scales have been developed to assess the recovery and progress of inpatients with TBI, attention has largely been focused on rehabilitation.[1] Few scales assess outcome across acute hospital and community settings. The Disability Rating Scale (DRS) is one such assessment tool.[2]

The DRS was developed and tested in patients with moderate and severe TBI especially while their rehabilitation is being achieved. The DRS has the ability to track an individual from the stage of coma to his rehabilitation in the community.[2] It measures recovery in three categories, that is, impairment, disability, and handicap. The first three items of the DRS (Eye Opening, Communication Ability, and Motor Response) represent the GCS and measure impairment. Cognitive ability for 'Feeding', 'Toileting', and 'Grooming' gives information about the level of disability. The Level of Functioning item is the modification of a measure used by Scranton et al., and reflects handicap, as does the last item “Employability.”[3] The lowest score is 0 that represents no disability. The highest score is 29 that represents the extreme vegetative state. The advantage of the scale is that it can be self-administered or scored through an interview with the participant or family members. Its brevity and the ease of administration has made it a popular scoring scale for assessing the outcome of TBI. The average time to administer it can range from 30 s to 15 min. An additional advantage is that it can be obtained by a phone interview.[4]

The DRS has good reliability and validity. The inter-rater reliability (IRR) of the DRS, as assessed by Pearson correlation or Spearman rho correlation coefficient, has been reported to range from 0.93 to 0.98 in the inpatient rehabilitation setting.[2],[5],[6] The concurrent validity of DRS with simultaneously obtained GOS scores at the time of discharge from rehabilitation centers ranges from 0.67 to 0.80 for GOS, and 0.85 for Glasgow Outcome Scale Extended (GOSE).[4] The predictive validity of DRS is good. In the original study of DRS, the initial scores correlated significantly (r = 0.53, P < 0.01, n = 77) with DRS 1 year later.[2] In one study, the correlation of DRS at admission in a rehabilitation center with the discharge GOSE was 0.73.[4] However, the predictive validity of DRS at the time of discharge from an acute care setting with the functional outcome at time of follow-up has not been determined. We conducted this study to determine if the condition at discharge from an acute care setting, as assessed by DRS, correlates with functional outcome, as measured by GOSE, at the time of follow up.


 » Materials and Methods Top


A prior approval from the institute's ethical committee was obtained, and informed consent was obtained from the relative or caregiver of the patient. All patients admitted to the neurosurgical intensive care unit (ICU) with a diagnosis of severe TBI, defined as post-resuscitation GCS of ≤ 8 after head trauma, were enrolled for the study. The patients underwent standard treatment except for intracranial pressure monitoring. Patients with extracranial injuries were not included. On the day of discharge, all patients underwent DRS assessment by a research scholar (AD), who underwent a prior training by a senior consultant (DS). The inter-rater reliability (IRR) was not determined because DRS assessment is routinely performed in our inpatient rehabilitation department. All patients' relatives/caregivers were given detailed instructions regarding the management of the patient required during the follow-up period, and were contacted periodically. A final assessment was performed telephonically using a structured interview for GOSE at 6 months after discharge from our hospital.[7],[8],[9] The outcome at 6 months was further dichotomized as favorable (good recovery and moderate disability) and unfavorable (severe disability, vegetative state, and death).

Statistical analysis

The correlation between the DRS scores at the time of discharge with DRS scores and GOSE categories at 6 months after discharge was determined using Spearman's rho correlation coefficient. The significance was determined at P = 0.01 (two-tailed). The accuracy of DRS at discharge in determining an unfavorable outcome and mortality at 6 months was determined using area under “receiver operating characteristics (ROC)” curve (AUC). The statistical analysis was done using the Statistical Package for the Social Sciences version 16 (SPSS Inc., Chicago, USA).


 » Results Top


A total of 88 patients were recruited in the study. The 6-month follow-up was available for 79 (89.8%) patients. The clinical and imaging profile during the time that the patient sustained injury is given in [Table 1]. The in-hospital mortality was 16%. Most patients underwent surgery for traumatic mass lesions. The duration of hospital stay ranged from 1 to 45 days. All patients had a DRS score of 7 or more, indicating moderately severe or worse disability [Table 2]. At 6-month follow-up duration, many patients improved and a few died. Mortality at 6 months was 30.4% [Table 2]. Favorable outcome was seen in 39.3% patients [Table 3].
Table 1: General demographic and clinical profile of patients

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Table 2: Disability rating scale (DRS) scores and category at time of discharge and follow up

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Table 3: Glasgow outcome scale extended scores and category at time of follow up

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The DRS of 63 patients who were alive at the time of discharge was used to correlate with the DRS score and GOSE at 6 months. The Spearman's rho correlation coefficient for DRS at discharge and DRS at 6 months was 0.536, which was significant at P = 0.01. The Spearman's rho correlation coefficient for DRS at discharge and GOSE at 6 months was −0.553, which was significant at P = 0.01 [Figure 1]. The concurrent validity of DRS with GOSE at 6 months was − 0.976, which was significant at P = 0.01. The negative value of correlation coefficient with GOSE is because of the scoring pattern; higher DRS score indicates more disability whereas higher GOSE indicates better recovery.
Figure 1: Scatter plots. (a) DRS at discharge vs. DRS at follow up. (b) DRS at discharge vs GOSE at follow up

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The accuracy of DRS score at discharge as measured by AUC for predicting an unfavorable outcome at 6 months was 0.770 (0.655–0.885), which is fair. The DRS score above 20 predicted an unfavorable outcome with 65.6% sensitivity and 71% specificity. The accuracy of DRS score at discharge as measured by AUC for predicting mortality at 6 months was 0.820 (0.689–0.952), which is good [Figure 2]. The DRS score above 21 predicted mortality at 6 months with 87.5% sensitivity and 72.7% specificity.
Figure 2: Receiver operating characteristics curve (ROC). (a) Unfavorable Outcome, (b) Mortality

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 » Discussion Top


The GOS and GOSE are the most frequently used outcome assessment tools. The GOSE is considered the gold standard for outcome assessment after TBI.[1] The GOSE can be administered in the outpatient department by professionals from a range of backgrounds and does not require special training. The GOSE is simple and quick to administer, and is valid and reliable when used in a face-to-face interview, telephonic interview, or in a questionnaire sent by mail.[1] However, in our country, follow-up after severe TBI is difficult to obtain. Many studies restrict the outcome data to in-hospital mortality because of lack of follow up. Although GOS is meant to assess outcome after recovery from TBI, and should be assessed at least 6 months after injury, many authors use GOS to describe the condition at discharge as the outcome at follow-up is not available. Considering this scenario, in our country, we need an outcome assessment tool that can be administered at the time of discharge from acute care, which can predict the functional outcome. McMillan et al., proposed Glasgow Outcome at Discharge Scale (GODS) to assess disability after brain injury in an inpatient setting.[10] The nomenclature used in this scale is identical to GOSE. The items are similar to that used in GOSE; however, their description is a little different to suit the inpatient scenario. The IRR of GODS was 0.982 (quadratic-weighted kappa). The concurrent validity with the DRS during the inpatient stay as determined by Spearman's rho was −0. 728. The predictive validity of GODS was highly associated with the GOSE after discharge (Spearman rho: 0.512). The GODS correctly predicted disability (GOSE) at follow-up with a sensitivity of 89% and specificity of 75%. In addition, the GODS had good predictive validity with DRS, and with physical, fatigue, and social subscales of the SF-36. However, the authors assessed the outcome at follow-up within a few weeks of discharge. Outcome after severe TBI should be assesses at 6 months after injury because many patients improve over time.[1] Moreover, follow-up after discharge was achieved in 53/77 (69%) cases, even though there was no significant difference between the patients with and without follow up. In a study that had utilized the GODS, more than three-fourth of the patients had mild TBI. A common scale for assessment for all severities of TBI may not be appropriate.[1],[11] The GODS has not been validated by other researchers.

The DRS has been used to track the recovery of patient in the inpatient rehabilitation setting.[4] In this setting, the predictive validity of DRS has been found to be good. The DRS has not been used in the acute care setting for predicting outcome. We used DRS to predict the functional outcome at follow up. We found a good concurrent validity of DRS with GOSE at follow-up. The predictive validity of DRS at discharge was moderately strong and significant for GOSE and DRS at follow up (Spearman rho: −0.553 and 0.536, respectively, at P = 0.01). The discriminatory power of DRS at discharge was fair for predicting an unfavorable outcome at 6 months, and was good for predicting mortality at 6 months.

The limitation of our study was a variable period of hospital stay. We did not use a strict criteria for discharge from the acute care stay. If the DRS is assessed at a fixed duration after acute intervention for all patients, then the predictability of the functional outcome is likely to be uniform. We did not determine the IRR of DRS. We have been using DRS in our neurorehabilitation ward for brain insults due to various causes including TBI, and hence we did not find it necessary to determine the IRR.[12]


 » Conclusion Top


The condition at discharge, as determined by DRS, is an appropriate outcome assessment tool. The predictive validity of DRS is fair to good in determining GOSE at follow up. Pending availability of a more accurate outcome assessment tool, DRS at discharge can be used as a surrogate predicter of outcome, which would correlate with that assessed utilizing GOSE at follow up. The assessement of DRS at a fixed duration after injury may improve accuracy in predicting outcome and needs to be studied further.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
 » References Top

1.
Shukla D, Devi BI, Agrawal A. Outcome measures for traumatic brain injury. Clin Neurol Neurosurg 2011;113:435-41.  Back to cited text no. 1
    
2.
Rappaport M, Hall KM, Hopkins K, Belleza T, Cope DN. Disability rating scale for severe head trauma: Coma to community. Arch Phys Med Rehabil 1982;63:118-23.  Back to cited text no. 2
    
3.
Scranton J, Fogel ML, Erdman WJ 2nd. Evaluation of functional levels of patients during and following rehabilitation. Arch Phys Med Rehabil 1970;51:1-21.  Back to cited text no. 3
    
4.
Wright J. The Disability Rating Scale [Internet]. Center for Outcome Measures of Brain Injury 2000. Available from: http://www.tbims.org/combi/drs. [Last cited on 2015 Apr 24].  Back to cited text no. 4
    
5.
Novack TA, Bergquist TF, Bennett G. Primary caregiver distress following severe head injury. J Head Trauma Rehabil 1992;6:69-77.  Back to cited text no. 5
    
6.
Gouvier WD, Blanton PD, LaPorte KK, Nepomuceno C. Reliability and validity of the Disability Rating Scale and the Levels of Cognitive Functioning Scale in monitoring recovery from severe head injury. Arch Phys Med Rehabil 1987;68:94-7.  Back to cited text no. 6
    
7.
Wilson JT, Pettigrew LE, Teasdale GM. Structured interviews for the Glasgow Outcome Scale and the extended Glasgow Outcome Scale: Guidelines for their use. J Neurotrauma 1998;15:573-85.  Back to cited text no. 7
    
8.
Lu J, Marmarou A, Lapane K, Turf E, Wilson L; IMPACT Group; American Brain Injury Consortium Study Participation Centers. A method for reducing misclassification in the extended Glasgow Outcome Score. J Neurotrauma 2010;27:843-52.  Back to cited text no. 8
    
9.
Pettigrew LE, Wilson JT, Teasdale GM. Reliability of ratings on the Glasgow Outcome Scales from in-person and telephone structured interviews. J Head Trauma Rehabil 2003;18:252-8.  Back to cited text no. 9
    
10.
McMillan T, Weir C, Ireland A, Stewart E. The Glasgow outcome at discharge scale: An inpatient assessment of disability after head injury. J Neurotrauma 2013;974:970-4.  Back to cited text no. 10
    
11.
Shukla D, Devi BI. Mild traumatic brain injuries in adults. J Neurosci Rural Pract 2010;1:82-8.  Back to cited text no. 11
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12.
Gupta A, Taly AB. Functional outcome following rehabilitation in chronic severe traumatic brain injury patients: A prospective study. Ann Indian Acad Neurol 2012;15:120-4.  Back to cited text no. 12
[PUBMED]  Medknow Journal  


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