Hot Off the Press: Comparison of Clinical Suspicion Versus a Clinical Prediction Rule When Evaluating Children Following Blunt Torso Trauma

Trauma is the leading cause of mortality among children in the United States.1 In spite of a lack of consensus guidelines, computed tomography (CT) has become the contemporary criterion standard for the evaluation of hemodynamically stable children following blunt torso trauma.2, 3 In 2013, the Pediatric Emergency Care Applied Research Network (PECARN) derived a clinical prediction instrument consisting of seven findings from history and physical examination that could be used to identify children at very low risk (≤0.1%) for intra-abdominal injury (IAI) requiring intervention following blunt torso trauma: no evidence of abdominal or thoracic wall trauma, Glasgow Coma Scale score > 13, no abdominal tenderness, no abdominal pain, no decreased breadth sounds, and no history of vomiting.4 This prediction instrument has been awaiting external validation as well as comparison to other commonly used risk stratification methods such as clinical suspicion. The study was a planned secondary analysis of the initial PECARN derivation study.4 Consecutive patients < 18 years old presenting to a participating emergency department (ED) following blunt torso trauma were included if clinicians specified an initial level of suspicion (<1, 1–5, 6–10, 11–50, or >50%) for IAI requiring acute intervention prior to the abdominal CT scan. Abdominal CT scans were obtained at the discretion of physicians in the ED. Clinician suspicion for IAIs was considered positive if the risk of this outcome was presumed to be ≥1%. Likewise, the patients were considered to be non-low risk for the clinical prediction instrument if any one of the seven variables in the instrument was present. Patients assigned a clinical suspicion of <1% or deemed low risk by the clinical prediction instrument were considered to be at very low risk for IAI requiring acute intervention (equivalent to a 0.1% risk of IAI in the derivation study). IAIs requiring acute intervention were defined as follows: death due to abdominal injury, surgical intervention, angiographic embolization due to bleeding, blood transfusion for anemia secondary to traumatic hemorrhage, or requiring intravenous fluids for two or more nights in patients with gastrointestinal injuries. The authors calculated and compared the test characteristics for both the prediction instrument and clinical suspicion (≥1%) for predicting patients with a significant IAI requiring acute intervention. One limitation to this study is that the clinical prediction instrument in question has not yet been externally validated so the test characteristics of this rule may be less favorable in the general population. Furthermore, the initial derivation study was conducted at specialized pediatric trauma referral centers so it is unclear how this instrument might perform in a community setting less accustomed to pediatric trauma patients. Importantly, however, the authors designed the prediction instrument to only include history and physical examination variables so that it could be widely used by clinicians regardless of access to ultrasound or specialized laboratory resources. Another weakness of the study was that CT scans were ordered at the treating physician's discretion. It is therefore possible that some IAIs requiring intervention could have been missed in spite of the authors’ well-designed follow-up analyses, potentially introducing differential verification bias.5 An important strength of this study was the use of a patient-centered outcome (IAIs requiring acute intervention) so that patients with benign, clinically insignificant IAIs may be able to safely forgo advanced imaging. A correlation between clinical suspicion and both rates of abdominal CT scanning and IAIs requiring acute intervention was noted. Among patients deemed to be at very low risk (<1%) by clinician suspicion, 35 of 9,252 (0.4%, 95% confidence interval [CI] = 0.3% to 0.5%) had IAIs requiring acute intervention. Of these 35 patients, only three (9%) were considered very low risk by the clinical prediction instrument. In contrast, among patients deemed to be very low risk by the prediction instrument, six of 5,040 patients (0.1%) were found to have IAIs requiring acute intervention. The clinical suspicions in these six patients were all ≤ 10%. The authors concluded that the sensitivity of the clinical prediction instrument (97.0%, 95% CI = 93.7% to 98.6%) significantly exceeded the sensitivity of clinical suspicion (82.8%, 95% CI = 77.0% to 87.3%). In contrast, the specificity of the prediction instrument (42.5%, 95% CI = 41.6% to 43.4%) was lower than the specificity of clinical suspicion (78.7%, 95% CI = 77.9% to 79.4%). Both risk stratification methods had similar negative likelihood ratios (prediction rule 0.1, 95% CI = 0.0 to 0.2; clinical suspicion 0.2, 95% CI = 0.2 to 0.3). Interestingly, the authors noted that nearly one-third (32.6%, 95% CI = 31.6% to 33.6%) of patients with very low (<1%) clinical suspicion for significant IAIs still received an abdominal CT scan, highlighting the potential overuse of imaging in this population.6 Because of the wide variation in CT utilization across different ED settings and the associated risks of harm from CT exposure (most notably radiation-induced cancers),7-9 physicians must use either informal (clinical gestalt) or formal methods (prediction instruments) for risk-stratifying patients to determine who is likely to benefit from a CT scan. In this study, the authors demonstrated that the clinical prediction instrument had a significantly higher sensitivity (but lower specificity) for identifying children with IAI requiring intervention in comparison to clinical suspicion. Interestingly, the higher specificity of clinical suspicion did not correlate well with clinical practice, as many children deemed to have “very low” suspicion for IAI requiring acute intervention still underwent a CT scan. These results underscore the need for further study as a validated prediction instrument could not only lead to potentially less “missed” injuries; it could also reduce the amount of unnecessary abdominal CT scans performed on very-low-risk children following blunt trauma. Currently, because this decision instrument is still awaiting proper validation, it should not be used in place of clinical judgment. Jeff Perry, University of Ottawa (comment on the Skeptics Guide to Emergency Medicine [SGEM] blog): The authors of this study are to be congratulated for their incredible work. This is a very large, well-conducted derivation study for a serious, but relatively rare clinical problem. Unfortunately the sensitivity of their proposed rule is 97% (94%–99%). This sensitivity is better than using the predictions by clinicians (with ≥1% being considered high risk; sensitivity of 83% [77%–88%]). However, physicians did not practice using this 1% cut point. They still investigated patients with a sensitivity of <1%. Therefore, it is doubtful that physicians will adopt a rule with 97% sensitivity, even if subsequently successfully validated. I hope that the authors are able to continue studying this problem to identify a more sensitive rule without drastically lowering the specificity. Otherwise, it is unlikely clinicians will use even a validated version of their rule. Suneel Upadhye, McMaster University (comment on the Skeptics Guide to Emergency Medicine [SGEM] blog): The value of any imaging CDR is the ability to be highly sensitive to rule OUT any significant disease so that imaging is not required. This rule does not meet this requirement with a sensitivity lower 95% CI of 76%, which misses one in four cases of significant abdominal injury. Increased utilization of CT scans with the CDR is also problematic … Kurt Eifling, Washington University in St. Louis (comment on the Skeptics Guide to Emergency Medicine [SGEM] blog): Yet the search should continue. The PECARN work that led to the derivation and validation of the use of head CTs after blunt head trauma … that has turned a common clinical scenario from muddy and spooky to a conversation about known risks, clear prognosis, and deliberate choices. I agree that blunt abdominal trauma is less common, and of such complexity that any signal in the data will likely be vague compared to the head trauma data. But if it eventually helps us bring an informed, understandable conversation to the bedside in this scenario, the grind of these authors’ hunt will be worthwhile. Michael Falk, SUNY Downstate Medical Center (comment on the Skeptics Guide to Emergency Medicine [SGEM] blog): Looking at the data and the study, I think we are still left with clinical judgment as the best option. I often do serial exams of the abdomen and use FAST to examine the belly and then make a decision. If it's late at night, keeping the patient till the am and then reassessing with surgery is always a great option. But if my clinical judgment is low and the FAST is negative, then I am comfortable with those types of plans. I would vote for “suspicious minds.” To maximize patient safety and minimize harm in the ED assessment of pediatric trauma victims, physicians must risk stratifying patients using their own clinical judgment to determine who is likely to have an IAI requiring acute intervention and therefore benefit from advanced imaging. The clinical prediction instrument proposed by Mahajan et al. shows promise, but still will require external validation. Although outside the scope of this article, diagnostic adjuncts in addition to history and physical exam exist and should be considered when evaluating pediatric trauma patients, including laboratory studies and ultrasound examinations in combination with simple observation and reevaluation.10

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