Pelvic CT Imaging in Blunt Abdominal Trauma
Condition: Blunt Abdominal Trauma
MeSH terms: Wounds and Injuries; Abdominal Injuries
Study type: Observational

Summary: 
      Abdominopelvic CT (CTap) utilization rose significantly in blunt trauma patients over the
      last decade. However, the observed increases failed to reduce mortality or missed injury
      rates. Several investigators have derived (citation) and validated (citation) clinical
      decision rules that attempt to identify a subset of low risk pediatric and adult patients in
      whom abdominopelvic CT imaging can be safely eliminated. Thus far these efforts failed to
      significantly reduce utilization. The investigators propose an alternative and complimentary
      strategy to decrease radiation by selectively eliminating the pelvic imaging portion of the
      abdominopelvic CT in low risk patients. In stable, alert patients without clinically evidence
      of pelvis or hip fractures, abdominal CT imaging alone (diaphragm to iliac crest) identifies
      clinically significant intra-abdominal injury (cs-IAI) as accurately as routine
      abdominopelvic imaging (diaphragm to greater trochanter) and results in a clinically
      important decrease in radiation exposure. The study will investigate this by comparing the
      accuracy of an imaging protocol using CT abdomen alone versus CT abdomen and pelvis to detect
      cs-IAI among stable, blunt trauma patients without suspected pelvis or hip fractures in two
      age groups: ages 3-17 years and 18-60. Patients will undergo CT imaging as deemed clinically
      indicated by the treating clinician. Among those who have abdominopelvic CT scans, the study
      will determine the test characteristics of CT abdomen alone versus CT abdomen plus CT pelvis
      imaging for the identification of cs-IAI. The reference standard will include initial
      radiology reports, with structured follow up of indeterminate scans, operative reports, and
      7-day medical record review.
    

Detailed description: 
      Abdominopelvic computed tomography (CTap) utilization rose significantly in blunt trauma
      patients over the last decade but failed to reduce mortality or missed injury rates.

      Primary Hypothesis: In stable, alert patients (GCS > 14) without clinically evident fractures
      of the pelvis, hip or lumbar spine, CT abdomen (CTa) alone (diaphragm to iliac crest)
      identifies intra-abdominal injury (IAI) with an accuracy that is not inferior to routine CTap
      (diaphragm to greater trochanter) with a clinically relevant reduction in radiation exposure.

      Primary Aim: Compare the accuracy of CTa alone versus CTap to detect IAI in two age groups:
      ages 3-17 years and 18-60 years. Blunt trauma patients requiring CTap will be enrolled. Data
      obtained prior to CT imaging include demographics, injury mechanism, exam and pelvic
      radiograph findings and FAST results from the trauma evaluation. The original CTap will be
      digitally reformatted to create matched pairs of de-identified CTa and CTap studies. A board
      certified study radiologist, blinded to the original CT and clinical outcome, will interpret
      the CTa studies in injured patients. McNemar's chi-square test will be used to evaluate the
      null hypothesis for injuries in matched pairs assuming no difference for uninjured patients.
      Te the test characteristics of the CTa versus CTap will be determined. The reference standard
      will include initial radiology reports, operative reports, and 7-day medical record review.
      If the upper limit of the 95% confidence interval for the difference in the performance
      (accuracy) of CTap and CTa alone is less than 3%, the conclusion will be that CTa alone is
      not inferior to CTap to diagnose IAI. Secondary Aims: The mean effective doses of radiation
      will be calculated and compared with reductions up to 50% expected. The study will determine
      if physicians' pretest probability accurately identifies clinically significant pelvis, hip
      and lumbar spine fractures (CTp indications) in two age groups: ages 3-17 years and 18-60
      years. Using a gestalt pretest probability of ≤ 2% as "negative for injury", and a pretest
      probability > 2% as "positive for injury", the test characteristics of physician estimation
      will be determined. The test characteristics and interobserver agreement (Cohen's kappa
      statistic) of exam findings expected to predict fractures of the pelvis, hip and lumbar spine
      will be reported separately.
    

Observational model: Cohort
Time perspective: Prospective
Sampling method: Probability Sample
Study population: 
        3-60 years of age evaluated for blunt trauma with a GCS of >14 Order of CT abdomen and
        pelvis imaging
      
Keywords: blunt abdominal trauma; CT; radiation exposure, pediatric