Role of Transthoracic Lung Ultrasonography in the Diagnosis of Pulmonary Embolism: A Systematic Review and Meta-Analysis

Abstract

Background: Pulmonary embolism (PE) is a potentially life-threatening condition. Although computed tomography pulmonary angiography (CTPA) is the reference standard for diagnosis, its early diagnosis remains a challenge, and the concerns about the radiation exposures further limit the general use of CTPA. The primary aim of this meta-analysis was to evaluate the overall diagnostic accuracy of transthoracic lung ultrasound (TLS) in the diagnosis of PE.

Methods: PubMed, Web of science, OvidSP, ProQuest, EBSCO, Cochrane Library and Clinicaltrial.gov were searched systematically. The quality of included studies was assessed using the Quality Assessment of Diagnostic Accuracy Studies-2 tool. The sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR) and hierarchical summary receiver operating characteristic (HSROC) curves were used to examine the TS performance. The Bayes analysis was used to calculate the post-test probability of PE. Publication bias was assessed with Deeks funnel plot.

Results: The results indicated that the sensitivity, specificity, PLR and NLR were 0.85 (95% confidence interval (CI), 0.78 to 0.90), and 0.83 (95% CI, 0.73 to 0.90). And the DOR and HSROC were 28.82 (95% CI, 17.60 to 47.21), 0.91(95% CI, 0.88, 0.93).

Conclusions: The present meta-analysis suggested that transthoracic lung ultrasonography is helpful in diagnosing pulmonary embolism. Although the application of transthoracic lung ultrasound may change some patients' diagnostic processes, it is inappropriate to generally use transthoracic ultrasonography in diagnosing pulmonary embolism currently.

Fig 1. Flow chart of study selection for inclusion in the systematic review.

Fig 2. Summary of QUADAS-2 assessments of included studies.

Fig 3. Forest plot for sensitivity and specificity.

Fig 4. Hierarchical summary receiver operating characteristic (HSROC) curves for the detection of pulmonary embolism using transthoracic ultrasonography.

Fig 5. The Deek’s funnel plot for the assessment of potential publication bias.

Fig 6. Fagan plot analysis to evaluate the clinical utility of transthoracic ultrasonography (TS) for the detection of pulmonary embolism (PE).

(a) With a pretest probability of PE of 1.3%, the post-test probability of PE, given positive and negative TS results, were 6% and 0%. (b) With a pretest probability of PE of 16.2%, the post-test probabilities of PE, given positive and negative TS results, were 50% and 3%. (c) With a pretest probability of PE of 40.6%, the post-test probability of PE, given positive and negative TS results, were 78% and 11%. The Fagan plot consists of a vertical axis on the left with the pretest probability, an axis in the middle representing the likelihood ratio, and a vertical axis on the right representing the post-test probability.

Fig 7. Fagan plot analysis to evaluate the clinical utility of transthoracic ultrasonography (TS) for the detection of pulmonary embolism (PE) from studies published post-2000.

(a) With a pretest probability of PE of 1.3%, the post-test probability of PE, given positive and negative TS results, were 8% and 0%. (b) With a pretest probability of PE of 16.2%, the post-test probabilities of PE, given positive and negative TS results, were 55% and 5%. (c) With a pretest probability of PE of 40.6%, the post-test probability of PE, given positive and negative TS results, were 81% and 15%. The Fagan plot consists of a vertical axis on the left with the pretest probability, an axis in the middle representing the likelihood ratio, and a vertical axis on the right representing the post-test probability.

Fig 8. The relationship between post-test probability and pre-test probability.