The present study was approved by the National Medical Ethics Committee of the Republic of Slovenia. All declarations were performed in accordance with the relevant guidelines and regulations. We performed a prospective observational cohort study over a one-and-a-half-year period, from March 2012 to September 2013.
We contact prehospital units in large community area in Slovenia. We send an introduction letter to colleagues describing the aim and procedures of the study. Recruitment materials includes: accurate description of the research purpose, name and address of the investigator, condition under study, plans of the study and investigator checklist, eligibility criteria of the patients, time commitments required, location of the research, written and illustrated material on GCS and FOUR score with links to web access for further explanations (official and dedicated web sites, videos…), sample excel tables of study data, medical ethics consent, informed consent, person to contact for further information. We also sent reminder letters to increase response rate among clinicians. We used email and SMS on scheduled time to colleagues, to re-evaluate patient’s outcome.
Our inclusion criteria were minor or moderate-to-severe TBI patients with altered mental status and/or coma who were either polytraumatized or had isolated head injuries. We did not include patients under the age of 18, patients who required CPR or patients who died before arriving at the hospital.
TBI patients were treated and evaluated by emergency prehospital medical unit personnel. The arrival time to the nearest regional hospital was up to 15 minutes. All patients were treated according to the ATLS guidelines.
We evaluated the GCS and FOUR scores in the prehospital setting at three different time points: immediately upon first contact with the patient at the scene, after management of the patient by the prehospital medical unit, and during patient handover by the ambulance staff at the hospital (Table 2). Outcome was assessed after 24 hours, 1 month and 3 months.
Table 2
GCS and FOUR in the prehospital setting.
Time point
|
Variable
|
Immediate first contact at the scene
|
GCS 1/FOUR 1
|
After the management of the patient at the scene
|
GCS 2/FOUR 2
|
Patient handover at the hospital
|
GCS 3/FOUR 3
|
The three different time points are as follows: immediately at first contact with the patient at the scene (GCS 1/FOUR 1), after the management of the patient by the prehospital medical unit (GCS 2/FOUR 2), and during patient handover by ambulance staff at the hospital (GCS 3/FOUR 3). |
We included 200 patients with TBI in our study (133 men and 67 women). The study size was obtained with a power analysis using GPower 3.1.9 software and z test for an a priori power calculation using alpha (α) of 0.05, power of 80% and effect size (d) of 0.8 calculated separately for FOUR and GCS scores. A priori power analysis has shown that for 80% power at least 107 vs. 15 or 27 vs. 27 individuals have to be included for allocation ratio of 0.14 or 1, respectively. Post-hoc statistical power of proportions is presented as sensitivity (1-β).
An overview of the clinical characteristics of the cohort study is shown in Table 3.
Table 3
Overview of the clinical characteristics of the cohort study.
Severity
|
Sex (M/F)
|
Age (years ± SD)
|
FOUR Eye Response (median/min/max)
|
FOUR Motor Response (median/min/max)
|
GCS Eye Response (median/min/max)
|
GCS Motor Response (median/min/max)
|
GOS-E (median/min/max)
|
Severe a
(N = 35)
|
23/12
|
59.0 ± 24.7
|
1/0/4
|
3/0/4
|
2/1/4
|
4/1/6
|
1/1/5
|
Moderate b
(N = 29)
|
24/5
|
47.9 ± 21.1
|
3/0/4
|
3/0/4
|
3/1/4
|
5/1/6
|
3/1/5
|
Mild c
(N = 121)
|
77/44
|
51.8 ± 24.1
|
4/0/4
|
4/0/4
|
4/1/4
|
6/1/6
|
5/1/5
|
Other d
(N = 15)
|
9/6
|
49.8 ± 17.3
|
4/0/4
|
4/0/4
|
4/1/4
|
6/1/6
|
5/1/5
|
a Head trauma - intracranial haemorrhage, brain oedema, severe loss of consciousness. |
b Head trauma - concussions with moderate loss of consciousness. |
c Head trauma without brain damage. |
d No head trauma. |
N: number of patients by severity classification |
The sensitivity, specificity, correct prediction and Youden’s J-statistic (index) [13] were obtained with a two-by-two table. Youden’s J-statistic was used to assess the performance of a dichotomous diagnostic test. For each scale and each outcome, all possible cut-off points were constructed by means of two-by-two tables. We calculated the sensitivity (true positive) by choosing survivors with equal or more points according to the selected cut-off point. In addition, we calculated the specificity (true negative), where we chose nonsurvivors with fewer points according to the selected cut-off point. The best cut-off points for each of the outcomes were further assessed and pairwise compared. The percentages of correct predictions of outcomes were obtained according to these cut-off points. For each score, receiver operating characteristic (ROC) curves were obtained [14–17]. The greater the area under the ROC curve was, the better the scoring system. Data were analysed with IBM SPSS Statistics for Windows, version 21.0. Armonk, NY: IBM Corp. The outcome prediction data were compared to the observed data using McNemar’s test for comparison of paired dichotomous categorical mutually exclusive variables in order to meet the assumptions. The comparisons of the areas under the ROC curves and the analyses of the differences in the Youden index were performed using the method described by Hanley and McNeil [14–17]. P < 0.05 was considered statistically significant.
Possible biases that could affect our study:
- In relation to data collection we spot a potential bias about doctors who may superficially perform GCS and FOUR score because of lack of skills, especially for a FOUR score. We skip that potential unfamiliarity, educating clinicians who performed and interpret the scores, exposing them to the same level of basic knowledge.
- We also detect a possible bias evaluating GCS and FOUR score in intubated and mechanically ventilated patients compared to patients who breath spontaneously. In these study, the amount of intubated and mechanically ventilated patients in the prehospital arena were insufficient to statistically influence the p value of the suggested models in our study.