Only Moderate Intra- and Inter-observer Agreement between Radiologists and Surgeons when Grading Blunt Paediatric Hepatic Injury on CT Scan

Introduction: The American Pediatric Surgical Association developed guidelines for the management of haemodynamically stable children with hepatic or splenic injury, based on grade of injury on CF scan. This study investigated the intra- and inter-observer agreement of radiologists, paediatric surgeons, trauma surgeons and hepatobiliary surgeons when scoring liver injury based on CT scan findings. Patients and Methods: CT scans of patients with blunt abdominal trauma were independently assessed twice by a fellow and a consultant radiologist, paediatric surgeon, trauma surgeon and one consultant hepatobiliary surgeon. Reviewers were unaware of the clinical course. All scans were multislice CTs with a slice thickness of 3 mm, and both the arterial and venous phase were assessed. Injury was scored using the American Association for the Surgery of Trauma (AAST) liver injury scale. Intra-observer agreement was tested using Cohen's kappa coefficient. Inter-observer agreement was tested using Cohen's kappa for the second reading of individual observers and Spearman's rank correlation for the mean of both readings from each observer. Results: CT scans of 27 patients (11 girls and 16 boys, median age 11.7 +/- 5.2 years) were reviewed. Mean AAST grade of liver injury was 3.3 +/- 1.1 for radiologists, 2.9 +/- 1.0 for paediatric surgeons, 3.0 +/- 0.9 for trauma surgeons and 3.2 +/- 0.8 for the hepatobiliary surgeon (p=0.30) Intra-observer agreement was moderate, with kappa below 0.7 for all observers except for one of the radiologists. Inter-observer correlation using Cohen's kappa coefficient was also moderate, with kappa below 0.5. In contrast, inter-observer correlation using Spearman's test was good, suggesting that there is agreement on the general severity of injury but not on the exact grading of injury using the AAST scoring system. Conclusion: Intra-observer agreement is only moderate when assessing liver injury using the AAST grading system. Only the most experienced radiologist demonstrated good intra-observer agreement which might indicate the necessity of the presence of a senior trauma radiologist at all times. However, this is not possible in most centres. Although there was agreement concerning the general severity of injury, inter-observer agreement is also moderate. These data cast doubt on the use of the AAST liver injury score alone as a decision-making tool when assessing haemodynamically stable children with blunt hepatic injury.