The Use of Injury Severity Score (ISS) to Assess The Economic Burden of Trauma at a Tertiary Care Center in Beirut, Lebanon

Abstract

Background: According to the Global Burden of Disease Study (GBD) in 2017, injuries are one of the leading causes of death and have accounted for 4.48 million deaths worldwide. It is also a disease of the youth. All injuries, regardless of the mechanism or category, were higher in the age group of 15-49 years. Injuries account for 10.1 % of all-age all-cause Disability-Adjusted Life Year (DALY) at 252 million DALYs. In addition to the significant mortality and morbidity, injuries have a significant economic burden in both developed and developing countries. The costs of injuries that result in a fatality were in the order of €1–6 billion euros in Europe in 2007, and when non-fatal injuries are included, this could rise to €290 billion. Even though organized trauma care systems were established within the health care systems of many developed countries and were effective in reducing the number of preventable trauma deaths and injury incidence, two-thirds of the total injury deaths are still occurring today in developing countries. Few studies have performed an economic assessment in low and middle-income countries (LMIC). To address the extent and burden of trauma, various models of injury scores were developed. The Injury Severity Score (ISS) is an established medical score to assess trauma severity that has been validated across different types of trauma and has proven to be reproducible across various studies. The ISS based on the Abbreviated Injury Scale (AIS) has been the gold-standard to assess trauma severity. A major trauma (or polytrauma) is defined as the Injury Severity Score being greater than 15. To our best knowledge, our study is the first to investigate the role of ISS in predicting the economic burden of trauma in Lebanon. Specifically, it will address the cost of care in the emergency department and in-hospital stay, in addition to the length of stay, at the American University of Beirut Medical Center (AUBMC), a tertiary care center in Beirut, Lebanon. The study aims to reflect on this association taking into consideration important clinical variables.

Hypotheses: Our hypotheses are: (1) the increase in the severity of the trauma, reflected by an increase in ISS score, will be significantly associated with the increase in the acute cost of care of patients admitted to the hospital through the emergency department (ED); (2) the increase in the severity of trauma will be significantly associated with the increase in the length of stay of patients admitted to the hospital through ED.

Objectives: Our primary objectives are to: (1) validate the association of ISS as a predictor of economic burden defined as the acute cost of care to trauma patients admitted to the hospital through ED. (2) assess possible confounders and effect modifiers that might affect ISS scores and acute cost of care respectively. Our secondary objectives are to: (3) establish a subgroup analysis of ISS scores (minor, moderate, and major trauma) and acute cost of care. (4) check the validity of ISS as a predictor of ED and hospital length of stay (LOS). (5) describe characteristics of trauma patients such as demographics, geographical location, injury patterns, clinical characteristics, management interventions, and outcomes

Methods: Data were obtained from a database created specifically to answer the above questions. The database involves 430 patients who presented to AUBMC ED from 2008 through 2013, with data obtained retrospectively from AUBMC EHR. Inclusion criteria are based on definitions used in building Trauma registries in the US. More specifically, codes from the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) were adopted. ICD-9 CM codes 800-999 stand for injury and poisoning. Patients with missing charts were excluded from the study. With a 95% confidence interval and significance level () 0.05, the Pearson correlation of two continuous variables (here cost and ISS) yields a sample size of n= 219. To account for a one-third missing data and other data access and storage problems the sample size will be increased to our convenient sample number which we collected at 430. Two researchers trained on the Collaborative Institutional Training Initiative (CITI) have completed data collection. ISS was calculated from AIS, and the cost was retrieved from the billing services. We did a descriptive analyses by calculating the mean and standard deviation for continuous, and number and percentage for categorical ones. We did inferential statistics, mainly bivariate analyses using the Chi-square test for categorical variables and independent Student’s t-test for continuous ones to assess any possible effect modifiers or confounders. For the primary objective, we studied the correlation between the continuous ISS score (range of 0-75) and the acute cost of care in USD via Pearson r correlation statistic assuming normal distribution (hence parametric distribution).

We implemented a multivariate analysis to identify predictors while controlling for potentially confounding variables, more specifically, multivariate linear regression analyses were used. We also performed a subgroup analysis to assess the relation of acute cost of care with the three categories of ISS (0-4: minor, 5-15: moderate, and ≥16 major trauma). P-values <0.05 will indicate statistical significance, and will not be corrected for secondary objectives.

Results: The total sample of the database from 2008 to 2013 included 431 patients with a mean age of 32.77 years. More than 50% of the population was younger than 26 years. The male to female ratio was 1.6 times. More than one-third of trauma patients were self-payers (35%), while half of them were covered by private insurance (50%), and the rest were either covered by national social security fund (NSSF) or other means (15%). Only 11.1 % of injuries occurred on motorways. The majority of injuries occurred via a blunt mechanism (65.4%). The ISS mean score of the sample was 6.399 (±7.794). There was a positive association between ISS and cost (R=0.279, R2=0.078, P<0.001). ISS could explain 7.8 percent of the cost. Similarly, when ISS was grouped into three levels of severity, there was a positive association with the cost for all subgroups. Minor injuries cost on average $230, moderate injuries $982, and severe injuries $1,6431 per admission. The use of EMS, class of admission, presence of specific comorbidities (diabetes, CAD, CHF, COPD, and cancer), performing ED labs, procedures in ED, and procedures in hospital significantly affects the cost. It is important to note that the location of injury was not associated with the cost of care. There was a positive association between ISS and Length of Stay in ED (R=0.313, R2=0.098, P<0.001). ISS can explain 9.8 percent of the length of stay in ED.

Conclusion: Our study has shown that trauma severity, assessed via ISS, is associated with a substantial economic burden on the Lebanese population. The multifactorial effect of comorbidities and lack of appropriate EMS increase the burden, highlighting the need to design an approach that also targets other non-communicable diseases and improves trauma provision. Further research is needed to form a national database to provide population-based data to inform local policymakers to implement preventive policies. An efficient and effective trauma and EMS system have been found to be a key component.