Date: November 21st, 2016
Reference: Eisenbrown et al. Which Febrile Children with Sickle Cell Disease Need a Chest X-Ray? AEM November 2016
Guest Skeptic: Dr. Corey Heitz is an associate professor of emergency medicine at the Virginia Tech Carilion School of Medicine in Roanoke Virginia. He is also the CME editor for Academic Emergency Medicine and the associate editor for emergency medicine simulation at the AAEM MedEdPORTAL.
Case: You are working in the Emergency Department on an overnight pediatric coverage shift. A worried mother brings her 2-year-old child in with a fever of 38.6C (that’s 101.5F). The female child’s medical history is significant for sickle cell disease. On exam, the child is uncomfortable appearing, tachycardic, tachypnic and febrile. Mom says the child has had a runny nose and a mild cough along with the fever.
Background: Children with sickle cell disease who develop fever are at higher risk of severe bacterial infection than children without sickle cell disease. The National Heart, Lung, and Blood Institute (NHLBI) suggest a routine workup that includes a CBC, blood cultures, and empiric antibiotics (NHLBI Expert Panel Report 2014).
One of the life-threatening infections for which these children are most at risk is acute chest syndrome (ACS). The NHLBI recommend a chest x-ray (CXR) for children with respiratory signs or symptoms (shortness of breath, tachypnea, cough, and/or rales).
Controversy exists as to whether the history and physical exam are sensitive enough to determine which febrile children need a CXR.
Clinical Question: Which febrile children with sickle cell disease presenting to the emergency department should get a CXR to help diagnose acute chest syndrome?
Reference: Eisenbrown et al. Which Febrile Children with Sickle Cell Disease Need a Chest X-Ray? AEM November 2016.
- Population: Children age three months to 21 years with sickle cell disease presenting to one of two children’s emergency departments with a fever of 38.4C or greater.
- Intervention: Accuracy of white blood cell count, history and physical exam findings to rule-in or rule-out acute chest syndrome.
- Comparison: None
- Primary Outcome: Presence of acute chest syndrome.
- Secondary Outcomes: Classification and regression tree (CART) analysis, sensitivity, specificity, positive and negative likelihood ratios of constellations of WBC, history/physical exam findings for acute chest syndrome.
The SGEM HOP episodes always have one of the authors on the show. Dr. David Brousseau is a Pediatric Emergency medicine physician at the Children’s Hospital of Wisconsin.
Author’s Conclusions: Children with SCD presenting to the ED with fever and shortness of breath, tachypnea, cough, rales, or chest pain should receive a CXR due to high ACS rates. A higher WBC count or history of ACS in a child without one of those symptoms may suggest the need for a CXR. Prospective validation of these criteria is needed.
- The study population included or focused on those in the ED. Yes
- The patients were representative of those with the problem. Yes
- All important predictor variables and outcomes were explicitly specified. Yes
- This is a prospective, multicenter study including a broad spectrum of patients and clinicians (level II). No, this was a retrospective chart review at two children’s hospitals
- Clinicians interpret individual predictor variables and score the clinical decision rule reliably and accurately. Yes
- This is an impact analysis of a previously validated CDR (level I). No
- For Level I studies, impact on clinician behavior and patient-centric outcomes is reported. Not applicable
- The follow-up was sufficiently long and complete Yes
- The effect was large enough and precise enough to be clinically significant. Yes
- Abstract Training – Were the abstractors trained before the data collection? Yes, but unclear how
- Case Selection Criteria –Were the inclusion and exclusion criteria for case selection defined? Yes
- Variable Definition – Were the variables defined? Yes
- Abstraction Forms – Did the abstractors use data abstraction forms? Yes
- Performance Monitored – Was the abstractors’ performance monitored? Yes
- Binding to Hypothesis– Were the abstractors aware of the hypothesis/study objectives? No
- Inter Rater Reliability (IRR) Mentioned – Was the interobserver reliability discussed? Yes, for the identification of fever
- IRR Tested – Was the interobserver reliability tested or measured? Yes, for the identification of fever
- Medical Record Identified – Was the medical record database identified or described? Yes, if by that you mean the population (2 hospitals, Jan 1 2010-Dec 31 2012, detailed inclusion criteria)
- Sampling Method – Was the method of sampling described? Yes, assuming this means the description of the sample size calculation.
- Missing Data Management Plan – Was the statistical management of missing data described? No
- Institutional Review Board Approved – Was the study approved by the institutional or ethics review board? Yes
Key Results: There were 1,837 febrile emergency department visits made by 697 children with sickle cell over two years. The median age was 3.5 years and it was a 50/50 male/female
Primary Outcome: 10% (185/1,837) of the febrile sickle cell children presenting to the emergency department met acute chest syndrome criteria.
- Secondary Outcomes: CART Model
- Using NHLBI guidelines alone, 27 cases of ACS would have been missed if no CXR was done but avoided CXRs in 45% (825/1,838) of children
- Using NHLBI or CP, 23 cases of ACS would have been missed (3%), increased sensitivity to 88% and would avoid CXRs in 43% (781/1,1837) of children
- Using NHLBI or CP or WBC>18.75, 12 cases of ACS would have missed (2), increased sensitivity to 94% and avoid CXRs in 32% (593/1,837) of children
- Using NHLBI or CP or WBC> 18.75 or history of ACS, 4 cases of ACS would have been missed, increased sensitivity to 98% and would avoid CXRs in 23% (430/1,837) of children
Listen to the podcast to hear Dr. Brousseau’s responses to our questions.
- Use of ICD-9 Codes: You used ICD-9 codes to identify children with sickle cell disease. Is this a validated method?
- Relying on Charting: You considered a patient having shortness of breath if something was documented on the chart but the absence of documentation of respiratory symptoms was treated as a negative. How do you think that could have influenced your results?
- Normal Range: We were impressed you used Fleming et al Lancet 2011 to determine tachypnea, a paper we have covered on SGEM#68.
- White Blood Cell (WBC) Count: Why did you pick WBC as the laboratory test when other tests also had significant differences?
- WBC Cut-Off: How did you decide >18.75 would be the cut off?
- Classification and Regression Tree (CART): You used CART analysis to determine predictive factors for a diagnosis of ACS. Can you explain the CART process?
- Acceptable Miss Rate: What is an acceptable miss rate for acute chest syndrome?
- Retrospective Chart Review: This was a retrospective chart review. While providing some information you do need to prospectively validate the results.
Comment on authors’ conclusion compared to SGEM Conclusion: We generally agree with the authors’ conclusions.
SGEM Bottom Line: Adding clinical features such as chest pain, WBC count >18.75 or history of ACS may improve sensitivity of criteria directing the decision to order a CXR in febrile sickle cell children presenting to the ED. A prospective validation study in febrile children with sickle cell disease presenting to the ED using these criteria is needed to determine which children should get a CXR to help diagnose acute chest syndrome.
Case Resolution: You obtain a CXR in your febrile patient with sickle cell disease, along with a complete blood count and blood cultures, and start empiric antibiotics. The CXR is negative for an acute infiltrate, and the patient is admitted to the hospital for further care.
Clinically Application: Getting a CXR in pediatric sickle cell disease patients presenting to the emergency department with NHLBI consensus criteria or chest pain will identify most cases of acute chest syndrome. However, getting a CXR in patients with WBC >18.75 count or history of acute chest syndrome is associated with an increased sensitivity while decreased specificity.
What do I tell my patient? During your discussion with the patient’s mother, you explain that the minimal respiratory symptoms her daughter has combined with a negative CXR make you feel comfortable that the patient does not have acute chest syndrome. However, febrile patients with sickle cell disease are still at high risk of serious bacterial illness, and you would like to admit her daughter to the hospital for treatment.
Keener Contest: Last weeks’ winner was Jaroslaw Gucwa from Poland. He knew the medial term for the “ketamine tiger“ is emergence delirium.
Listen to the podcast for this weeks’ keener contest question. If you know the answer then email it to me at TheSGEM@gmail.com and the first correct answer will receive a cool skeptical prize.
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