Point-of-care lung ultrasonography for early identification of mild COVID-19: a prospective cohort of outpatients in a Swiss screening center
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Abstract
Early identification of SARS-CoV-2 infection is important to guide quarantine and reduce transmission. This study evaluates the diagnostic performance of lung ultrasound (LUS), an affordable, consumable-free point-of-care tool, for COVID-19 screening.
Design, setting and participants
This prospective observational cohort included adults presenting with cough and/or dyspnoea at a SARS-CoV-2 screening centre of Lausanne University Hospital between 31 March and 8 May 2020.
Interventions
Investigators recorded standardised LUS images and videos in 10 lung zones per patient. Two blinded independent experts reviewed LUS recording and classified abnormal findings according to prespecified criteria to investigate their predictive value to diagnose SARS-CoV-2 infection according to PCR on nasopharyngeal swabs (COVID-19 positive vs COVID-19 negative).
Primary and secondary outcome measures
We finally combined LUS and clinical findings to derive a multivariate logistic regression diagnostic score.
Results
Of 134 included patients, 23% (n=30/134) were COVID-19 positive and 77% (n=103/134) were COVID-19 negative; 85%, (n=114/134) cases were previously healthy healthcare workers presenting within 2–5 days of symptom onset (IQR). Abnormal LUS findings were significantly more frequent in COVID-19 positive compared with COVID-19 negative (45% vs 26%, p=0.045) and mostly consisted of focal pathologic B lines. Combining clinical findings in a multivariate logistic regression score had an area under the receiver operating curve of 80.3% to detect COVID-19, and slightly improved to 84.5% with the addition of LUS features.
Conclusions
COVID-19-positive patients are significantly more likely to have lung pathology by LUS. However, LUS has an insufficient sensitivity and is not an appropriate screening tool in outpatients. LUS only adds little value to clinical features alone.
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SciScore for 10.1101/2021.03.23.21254150: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Institutional Review Board Statement Consent: Written informed consent was obtained from all participants.
IRB: The study was approved by the Swiss Ethics Committee of the canton of Vaud (CER-VD 2019-02283).Randomization not detected. Blinding For interpretation of LUS pathology, a physician experienced in LUS (TB) and an expert radiologist (JYM), blinded to patients’ diagnoses, independently filled a standardized report form as previously described [8]. Power Analysis It was calculated using a COVID prevalence of 20% and an estimated sensitivity of LUS to identify COVIDpos at 80% This sample size guarantees a power of 80% with a false discovery rate of 5% [10]. Sex as a biological variable not detected. T…
SciScore for 10.1101/2021.03.23.21254150: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Institutional Review Board Statement Consent: Written informed consent was obtained from all participants.
IRB: The study was approved by the Swiss Ethics Committee of the canton of Vaud (CER-VD 2019-02283).Randomization not detected. Blinding For interpretation of LUS pathology, a physician experienced in LUS (TB) and an expert radiologist (JYM), blinded to patients’ diagnoses, independently filled a standardized report form as previously described [8]. Power Analysis It was calculated using a COVID prevalence of 20% and an estimated sensitivity of LUS to identify COVIDpos at 80% This sample size guarantees a power of 80% with a false discovery rate of 5% [10]. Sex as a biological variable not detected. Table 2: Resources
Software and Algorithms Sentences Resources R Core Team (2019) statistical software and python 3.0 with the sklearn library was used for analyses. pythonsuggested: (IPython, RRID:SCR_001658)Results from OddPub: Thank you for sharing your data.
Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:Limitations: Our study has some limitations. First, most of our subjects were healthy and young healthcare workers, which prevents extrapolation of our results to an older and comorbid population. However, young, healthy subjects are of a prime importance in the management of the virus spread [26]. Second, SARS-CoV-2 Rt-PCR nasopharyngeal swab was used as the gold standard, and we might have missed some early infections when it has limited sensitivity [27]. However, it is considered as the reference diagnostic method. Furthermore, we sought to mitigate technical and sample collection error using validated nucleic acid amplification tests and a dedicated trained medical team performing nasopharyngeal swabs [28]. In addition, we had 30-day follow-up, which may have reduced the number of patients misclassified as COVIDneg. To better investigate the predictive potential of LUS findings, we built a multivariate score. The small sample size and high feature count (n= 22) exposes the model to the risk of overfitting. Thus, this score is not ready for clinical use, but rather is a mean to demonstrate the feature importance by RFE.
Results from TrialIdentifier: No clinical trial numbers were referenced.
Results from Barzooka: We did not find any issues relating to the usage of bar graphs.
Results from JetFighter: We did not find any issues relating to colormaps.
Results from rtransparent:- Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
- Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
- No protocol registration statement was detected.
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