Abstract
Objectives Acute dyspnea is a common presenting complaint to the emergency department (ED), and point-of-care (POC) lung ultrasound (US) has shown promise as a diagnostic tool in this setting. The primary objective of this systematic review was to determine the sensitivity and specificity of US using B-lines in diagnosing acute cardiogenic pulmonary edema (ACPE) in patients presenting to the ED with acute dyspnea. Methods A systematic review protocol adhering to Cochrane Handbook guidelines was created to guide the search and analysis, and we searched the following databases: PubMed, EMBASE, Ovid MEDLINE, Ovid MEDLINE In-Process & Other Non-Indexed Citations, and the Cochrane Database of Systematic Reviews. References of reviewed articles were hand-searched, and electronic searches of conference abstracts from major emergency medicine, cardiology, and critical care conferences were conducted. The authors included prospective cohort and prospective case-control studies that recruited patients presenting to hospital with symptomatic, acute dyspnea, or where there was a clinical suspicion of congestive heart failure, and reported the sensitivity and specificity of B-lines in diagnosing ACPE. Studies of asymptomatic individuals or in patients where there was no suspicion of ACPE were excluded. The outcome of interest was a diagnosis of ACPE using US B-lines. A final diagnosis from clinical follow-up was accepted as the reference standard. Two reviewers independently reviewed all citations to assess for inclusion, abstracted data, and assessed included studies for methodologic quality using the QUADAS-2 tool. Contingency tables were used to calculate sensitivity and specificity. Three subgroup analyses were planned a priori to examine the effects of the type of study, patient population, and lung US protocol employed. Results Seven articles (n=1,075) were identified that met inclusion criteria (two studies completed in the ED, two in the intensive care unit [ICU], two on inpatient wards, and one in the prehospital setting). The seven studies were rated as average to excellent methodologic quality. The sensitivity of US using B-lines to diagnosis ACPE is 94.1% (95% confidence interval [CI]=81.3% to 98.3%) and the specificity is 92.4% (95% CI=84.2% to 96.4%). Preplanned subgroup analyses did not reveal statistically significant changes in the overall summary estimates, nor did exclusion of three potential outlier studies. Conclusions This study suggests that in patients with a moderate to high pretest probability for ACPE, an US study showing B-lines can be used to strengthen an emergency physician's working diagnosis of ACPE. In patients with a low pretest probability for ACPE, a negative US study can almost exclude the possibility of ACPE. Further studies including large numbers of ED patients presenting with undifferentiated dyspnea are required to gain more valid and reliable estimates of test accuracy in ED patients.