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Importance: Standard tools used to diagnose pulmonary edema in acute decompensated heart failure (ADHF), including chest radiography (CXR), lack adequate sensitivity, which may delay appropriate diagnosis and treatment. Point-of-care lung ultrasonography (LUS) may be more accurate than CXR, but no meta-analysis of studies directly comparing the 2 tools was previously available.
Objective: To compare the accuracy of LUS with the accuracy of CXR in the diagnosis of cardiogenic pulmonary edema in adult patients presenting with dyspnea.
Data Sources: A comprehensive search of MEDLINE, Embase, and Cochrane Library databases and the gray literature was performed in May 2018. No language or year limits were applied.
Study Selection: Study inclusion criteria were a prospective adult cohort of patients presenting to any clinical setting with dyspnea who underwent both LUS and CXR on initial assessment with imaging results compared with a reference standard ADHF diagnosis by a clinical expert after either a medical record review or a combination of echocardiography findings and brain-type natriuretic peptide criteria. Two reviewers independently assessed the studies for inclusion criteria, and disagreements were resolved with discussion.
Data Extraction and Synthesis: Reporting adhered to the Cochrane Handbook for Systematic Reviews of Diagnostic Test Accuracy and the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. Two authors independently extracted data and assessed the risk of bias using a customized QUADAS-2 tool. The pooled sensitivity and specificity of LUS and CXR were determined using a hierarchical summary receiver operating characteristic approach.
Main Outcomes and Measures: The comparative accuracy of LUS and CXR in diagnosing ADHF as measured by the differences between the 2 modalities in pooled sensitivity and specificity.
Results: The literature search yielded 1377 nonduplicate titles that were screened, of which 43 articles (3.1%) underwent full-text review. Six studies met the inclusion criteria, representing a total of 1827 patients. Pooled estimates for LUS were 0.88 (95% Cl, 0.75-0.95) for sensitivity and 0.90 (95% Cl, 0.88-0.92) for specificity. Pooled estimates for CXR were 0.73 (95% CI, 0.70-0.76) for sensitivity and 0.90 (95% CI, 0.75-0.97) for specificity. The relative sensitivity ratio of LUS, compared with CXR, was 1.2 (95% CI, 1.08-1.34; P < .001), but no difference was found in specificity between tests (relative specificity ratio, 1.0; 95% CI, 0.90-1.11; P = .96).
Conclusions and Relevance: The findings suggest that LUS is more sensitive than CXR in detecting pulmonary edema in ADHF; LUS should be considered as an adjunct imaging modality in the evaluation of patients with dyspnea at risk of ADHF.
|Family Medicine (FM)/General Practice (GP)|
|General Internal Medicine-Primary Care(US)|
The lack of blinding of outcome adjudicators to CXR, the incorporation of CXR as part of the reference standard, and small number of studies are the major limitation. Sensitivity of lung ultrasonography between studies are very different from 0.58 to 0.97.
This review suggests that lung ultrasound (US) is more sensitive than CXR for acute heart failure (HF). That may be true, but there are some limitations. The authors don`t provide a statistical measure of heterogeneity, but 2 of the 6 included studies found much lower sensitivity (58% and 63%) for lung US (LUS) than the point estimate in meta-analysis. Different studies used different protocols and different thresholds to diagnosis HF by LUS, and LUS was interpreted by US experts, or at least those with some interest in studying LUS. Alternatively, CXR probably benefited from incorporation bias by the CXR findings being included in the "gold standard" of expert chart review to determine whether the patient actually had HF. These results for CXR are better than in previous meta-analyses. Learning how to look for B lines on LUS is actually easier than most US skills. If you have any proficiency in US, LUS is probably a useful, but far from definitive, test for acute HF.
High-quality systematic review providing expanding evidence of the diagnostically accurate superiority of POCUS over standard CXR for acute decompensated CHF exacerbation.
Interesting concept but I am not aware of anyone who is doing this in my institution. I suppose there must be a learning curve and, the more you do, the sensitivity and specificity may go up.
Comparison of both positive and negative LRs between the two testing methods gives the following: +LR = 7.3 CXR vs 8.8 LUS; -LR = 0.3 CXR vs 0.13 LUS. While LUS is better at both diagnosing and ruling out pulmonary edema from CHF, it is the sensitivity difference (the power in ruling out) that is the important feature to weigh in this analysis. Consider that LUS is reported to cost $140 and CXR costs $370 (found on line at a hospital in NYC). The difference in -LR between the two studies finds LUS 2.3 times better at ruling out disease. So for every LUS ordered at $140, it will take 2.3 CXRs at $370, or a cost of $850, which is $710 more than LUS to achieve the same rule-out diagnostic yield with CXR than with LUS. So, the better ability to rule out with LUS is an amazing savings as well. This finding will definitely change my diagnostic choices.
This study suggests that a prospective study comparing these 2 modalities would be appropriate given the limitations of this retrospective review. Unfortunately, there is probably no perfect reference standard to use to compare them to calculate sensitivity and specificity. Also, US use is highly operator-dependent, and the number of trained operators is limited at this time.