Lung Ultrasound Is Effective for Screening for Sickle Cell Acute Chest Syndrome

Using LUS to diagnose ACS in sickle cell disease allows for more rapid diagnosis in the ED and spares patients from ionizing radiation exposure.

Lung ultrasound (LUS) has excellent sensitivity and very good specificity for diagnosing acute chest syndrome (ACS) in patients with sickle cell disease (SCD), according to findings of a systematic review and meta-analysis published in Chest.

“Lung ultrasound is emerging as a point-of-care method to diagnose ACS, allowing for more rapid diagnosis in the emergency room setting and sparing patients from ionizing radiation exposure,” review researchers explained. The review and meta-analysis evaluated the diagnostic test accuracy of LUS for ACS using the current reference standard of chest x-ray (CXR).

Researchers conducted a literature search on March 17, 2022, in the Embase, MEDLINE, Web of Science, and Google Scholar databases. Eligible studies reported data from patients with SCD of any genotype, had a sample size of at least 5 patients, and provided data on test characteristics of LUS compared with the reference standard of CXR for ACS.

A total of 6 prospective, observational studies were included in the quantitative synthesis; of these, 4 were conducted in the US, 1 in France, and 1 in Brazil; 5 were conducted in pediatric emergency departments; and 2 studies were reported in conference abstracts. The studies yielded data for 625 possible cases of ACS and 95 confirmed diagnoses of ACS (pre-test probability, 15.2%).

Regarding the overall diagnostic accuracy of LUS, the area under the curve (AUC) was 0.96 (95% CI, 0.94-0.97), with a summary sensitivity of 0.92 (95% CI, 0.68-0.98) and a summary specificity of 0.89 (95% CI, 0.69-0.97). The summary positive likelihood ratio (LR) was 8.4 (95% CI, 3.0-23.6), with a summary negative LR of 0.09 (95% CI, 0.02-0.38). The summary positive predictive value was 0.88 (95% CI, 0.81-0.95), the summary negative predictive value was 0.90 (95% CI, 0.83-0.98), and the cumulative diagnostic odds ratio was 89 (95% CI, 32-244).

The results of our meta-analysis demonstrate that LUS may be a valuable tool in the evaluation of ACS in patients with SCD due to the lack of radiation exposure, low cost, and ease of use, especially in pediatric populations.

A sensitivity analysis conducted after the abstract-only studies were excluded showed a summary sensitivity of 0.87 (95% CI, 0.58-0.97), with a summary specificity of 0.92 (95% CI, 0.77-0.97) and AUC of 0.96 (95% CI, 0.94-0.97). The summary positive LR and summary negative LR were 10.8 (95% CI, 4.1-28.3) and 0.14 (95% CI, 0.04-0.52), respectively. The summary positive predictive value and summary negative predictive value were 0.90 (95% CI, 0.84-0.96) and 0.86 (95% CI, 0.81-0.92), respectively. The cumulative diagnostic odds ratio was 78 (95% CI, 30-206).

The between-study heterogeneity was I2 = 67.01% (95% CI, 38.40-95.63) for sensitivity and I2 = 97.36% (95% CI, 96.21-98.50) for specificity, based on the midas STATA command.

The researchers noted that all I2 values should be interpreted with caution because only 6 studies were included. Other limitations are the inclusion of conference abstracts and the fact that most studies included only patients who presented to the emergency department. In addition, there are no established sonographic findings for the diagnosis of ACS using LUS.

“The results of our meta-analysis demonstrate that LUS may be a valuable tool in the evaluation of ACS in patients with SCD due to the lack of radiation exposure, low cost, and ease of use, especially in pediatric populations,” stated the investigators. “Our results show that LUS provided excellent sensitivity and good specificity, favoring the use of LUS as an initial screening tool for ACS.”

Disclosure: One of the study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.

References:

Omar M, Jabir AR, Khan I, Novelli EM, Xu JZ. Diagnostic test accuracy of lung ultrasound for acute chest syndrome in sickle cell disease: a systematic review and meta-analysis. Chest. Published online December 9, 2022. doi:10.1016/j.chest.2022.11.042