Nishad Rahman, MD
Cohen, S. G., et al. (2020, September 1). Utility of Point-of-Care Lung Ultrasonography for Evaluating Acute Chest Syndrome in Young Patients With Sickle Cell Disease. Annals of Emergency Medicine, 76(3), S46-S55. https://doi.org/10.1016/j.annemergmed.2020.08.012.
Prospective observational study
The objective of this study was to determine the accuracy of point-of-care lung ultrasound compared to the gold standard of chest X-ray in identifying an infiltrate suggestive of acute chest syndrome in patients with sickle cell disease.
Acute chest syndrome is the leading cause of mortality in patients with sickle cell disease, and therefore this is a question with significant clinical relevance. As a result, these patients experience multiple radiological exposures starting at very young ages. If ultrasound is comparable to the current gold standard of chest radiography, patients with sickle cell disease may experience significantly less radiation exposure over their lifetimes.
This prospective observational study was conducted at 2 freestanding urban pediatric centers between November 2015 and July 2017. The study population was a convenience sample based on the availability of ultrasonographers. Exclusion factors included hemodynamic instability, chest radiography at an outside institution, and unavailability of a study ultrasonographer. Inclusion factors included documented sickle cell disease, aged 0-21 years old, and chest radiography within the current admission. Symptoms concerning for acute chest syndrome included chest pain, fever, vomiting, and respiratory symptoms such as cough. Ultrasonography was performed by sonographers who were blinded to physical examination and chest radiographic findings, ideally before chest radiography was performed.
Study sonographers included one expert blinded reviewer with 6 years of experience and specialized training in point-of-care lung ultrasonography, as well as five novice ultrasound trainees. The 5 novice sonographers underwent a 1-hour lecture on lung ultrasonography, a 1-hour practical hands-on imaging session, and 5 point-of-care lung ultrasonographic examinations before enrolling patients in the study. Consolidated lung findings by ultrasound were characterized by a hypoechoic region with irregular borders containing hyperechoic air bronchograms, requiring measurement greater than 1 cm to be determined positive. This is because consolidations less than 1 cm are often not identified on chest radiography. The expert sonographer was blinded to any previous interpretation and reviewed all studies that were performed.
Secondary outcomes included patient or guardian satisfaction, tolerability of the examination, and inter-operator reliability between trainees and the expert blinded reviewer. Satisfaction was assessed through a 10-question survey, using a Likert scale of 1 to 5 (1 being the least satisfied and 5 being the most satisfied). Satisfaction questions included queries about the entire ED visit as well as specific questions concerning the experience with point-of-care lung ultrasonography, including measures such as “pain and comfort during the scan, efficiency of the scan, whether the patient and family would like a point-of-care lung ultrasonographic examination at subsequent visits, how the scan affected interactions with healthcare providers, and the total patient experience in the ED.” The gold standard was the pediatric radiologist’s interpretation of the chest radiography.
Based on the afore-mentioned inclusion and exclusion criteria, 220 patients were eligible for participation. Of these, 21 patients declined enrollment, ultrasonography was incomplete for 7 patients, and 1 patient withdrew in the middle of examination due to discomfort. Ultimately, 191 patients were included in the data analysis.
This is a prospective observational study, which is not randomized or double-blinded. This study design is intrinsically at risk for confounding factors and potential selection bias. Furthermore, observational studies are only able to support correlation, never causation.
Included only six study ultrasonographers
Only 191 patients were enrolled out of possible 220. The small study size can skew the results and subsequent conclusions by encapsulating only a limited group, which is not generalizable to the general population.
Included only two centers
Convenience sample based on availability of ultrasonographers
Included only pediatric patients, so not generalizable to adults
This study makes me more likely to perform a screening point-of-care lung ultrasound searching for a consolidation of greater than 1 cm prior to ordering a chest X ray in young patients concerning acute chest syndrome, a life threatening complication in sickle cell disease.