Moving beyond personnel and process - A case for incorporating outcome measures in the trauma center designation process

Division of Burn, Trauma, and Surgical Critical Care, Department of Surgery, University of Texas Southwestern Medical Center, Dallas, TX 75390-9158, USA.
Archives of surgery (Chicago, Ill.: 1960) (Impact Factor: 4.3). 03/2008; 143(2):115-9; discussion 120. DOI: 10.1001/archsurg.2007.29
Source: PubMed

ABSTRACT Similarly designated trauma centers do not achieve similar outcomes.
Outcomes study.
Academic research.
Forty-seven American College of Surgeons-verified level I trauma centers that contributed more than 1000 patients to the National Trauma Data Bank (from January 1999 to December 2003) were identified.
Patients were classified into the following 3 injury severity groups using a combination of anatomical and physiological measures: mild (Injury Severity Score [ISS] of <25 with systolic blood pressure [SBP] of >/=90 mm Hg [n = 184 650]), moderate (ISS of >/=25 with SBP of >/=90 mm Hg or ISS of <25 with SBP of <90 mm Hg [n = 22 586]), and severe (ISS of >/=25 with SBP of <90 mm Hg [n = 4243]). The mean survival for each group was calculated. Individual centers were considered outliers if their patient survival was statistically significantly different from the mean survival for each severity group.
The mean survival of patients with mild, moderate, and severe injuries was 99%, 75%, and 35%, respectively. For mild injuries, survival at 5 centers (11%) was significantly worse than that at their counterpart centers. With increasing injury severity, the percentages of outcome disparities increased (15% of centers for moderate injuries and 21% of centers for severe injuries) and persisted in subgroups of patients with head injuries, patients sustaining penetrating injuries, and older (>55 years) individuals.
When treating patients with similar injury severity, similarly designated level I trauma centers may not achieve similar outcomes, suggesting the existence of a quality chasm in trauma care. Trauma center verification may require the use of outcome measures when determining trauma center status.

  • [Show abstract] [Hide abstract]
    ABSTRACT: To develop a statistically rigorous trauma mortality prediction model based on empiric estimates of severity for each injury in the abbreviated injury scale (AIS) and compare the performance of this new model with the injury severity score (ISS). Mortality rates at trauma centers should only be compared after adjusting for differences in injury severity, but no reliable measure of injury severity currently exists. The ISS has served as the standard measure of anatomic injury for 30 years. However, it relies on the individual injury severities assigned by experts in the AIS, is nonmonotonic with respect to mortality, and fails to perform even as well as a far simpler model based on the single worst injury a patient has sustained. This study is based on data from 702,229 injured patients in the National Trauma Data Bank (NTDB 6.1) hospitalized between 2001 and 2005. Sixty percent of the data was used to derive an empiric measure of severity of each of the 1322 injuries in the AIS lexicon by taking the weighted average of coefficients estimated using 2 separate regression models. The remaining 40% of the data was use to create 3 exploratory mortality prediction models and compare their performance with the ISS using measures of discrimination (C statistic), calibration (Hosmer Lemeshow statistic and calibration curves), and the Akaike information criterion. Three new models based on empiric AIS injury severities were developed. All of these new models discriminated survivors from nonsurvivors better than the ISS, but one, the trauma mortality prediction model (TMPM), had both better discrimination [ROCTMPM = 0.901 (0.898-0.905), ROCISS = 0.871 (0.866-0.877)] and better calibration [HLTMPM = 58 (35-91), HLISS = 296 (228-357)] than the ISS. The addition of age, gender, and mechanism of injury improved all models, but the augmented TMPM dominated ISS by every measure [ROCTMPM = 0.925(0.921-0.928), ROCISS = 0.904(0.901-0.909), HLTMPM = 18 (12-31), HLISS = 54 (30-64)]. Trauma mortality models based on empirical estimates of individual injury severity better discriminate between survivors and nonsurvivors than does the current standard, ISS. One such model, the TMPM, has both superior discrimination and calibration when compared with the ISS. The TMPM should replace the ISS as the standard measure of overall injury severity.
    Annals of surgery 06/2008; 247(6):1041-8. DOI:10.1097/SLA.0b013e31816ffb3f
  • [Show abstract] [Hide abstract]
    ABSTRACT: Evaluation of trauma center performance has been limited to comparisons of observed versus expected mortality using trauma and injury severity score methodology. Few studies have focused on identifying top performers. In part, this is due to the perceived need for extensive data required to adequately risk adjust. We set out to identify the patient and injury-related factors that most affect case-mix across centers and thus are most likely to alter assessments of hospital performance. One hundred ninety trauma centers contributing data to the National Trauma Databank (NTDB) during 2004 to 2005 were used for hospital rankings (n = 169,929 patients). Trauma centers were ranked by crude mortality. We then added variables [injury severity score {ISS}, systolic blood pressure {SBP}, mechanism, age, gender, comorbidities, body region abbreviated injury scale {AIS}] singly to a risk-adjustment model to obtain adjusted probability of death. Trauma centers were then ranked again. The variable that affected rankings the greatest was kept and the process was repeated in an iterative fashion until the incremental change in ranks was minimal. ISS accounted for the most variation in mortality rates across trauma centers, shown by the large rank change with addition of ISS to the model. Specifically, when ISS was taken into consideration, 92% of trauma centers changed their rank by >/=3 and almost half their quartile rank by at least 1. In lesser order of importance, age, SBP, head AIS, mechanism, gender, and abdominal AIS were relevant to adjust for case mix. Trauma center rankings are affected by few parameters, reflecting their relationship to mortality and their relative frequencies. Complex risk adjustment methodology is not required to address differences in case mix. Data abstraction for the purpose of comparing trauma center performance should focus on ensuring that at minimum, these variables are collected with a high degree of accuracy.
    The Journal of trauma 10/2008; 65(3):628-35. DOI:10.1097/TA.0b013e3181837994
  • [Show abstract] [Hide abstract]
    ABSTRACT: Mortality rates vary across designated trauma centers (TC), even after controlling for injury severity. Retrospective analysis of state trauma registry data. Designated Level 1 and 2 TCs in 2003 in a large Southwestern state. Adult trauma patients (n = 18,584) treated at 15 designated Level 1 and 2 TCs. Risk-adjusted survival was calculated for each trauma center using logistic regression analysis to adjust for differences in age, sex, race, injury mechanism, and injury severity. The model was developed using half of the study population and validated in the remaining half. It was then applied to the entire study population, with inclusion of TC identification codes. Observed vs Expected survival ratios were then calculated for each TC. Adjusted odds ratios (OR) for survival at each TC were also calculated. Adjusted OR of survival were significantly different from crude OR at 6 of the 14 TCs, underscoring the importance of risk adjustment when performing quality comparisons. One TC performed significantly worse than the others, 8 achieved significantly better survival, and 5 performed the same as the referent. Observed vs Expected ratios demonstrated that one trauma center had significantly worse severity-adjusted outcomes, some were marginal, some performed as well as expected, and none performed better than expectations. Considerable variations in risk-adjusted mortality rates exist across similarly designated TCs. Such variability in outcomes may reflect variations in quality of care, and reasons for this discrepancy should be explored as the next step in the trauma care quality improvement process.
    Archives of surgery (Chicago, Ill.: 1960) 02/2009; 144(1):64-8. DOI:10.1001/archsurg.2008.509