Utility of lung ultrasound assessment for probable SARS-CoV-2 infection during pregnancy and universal screening of asymptomatic individuals.

Abstract

Pregnant women are a risk group for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, which has been shown to be associated with increased rates of preterm delivery and Cesarean section1. Despite reassuring safety profile, imaging modalities, such as computed tomography, are used scarcely in pregnancies with suspected SARS-CoV-2 infection due to concerns about undue exposure of the fetus to ionizing radiation. However, false-positive and false-negative results are not uncommon in reverse transcription polymerase chain reaction (RT-PCR) testing. Anecdotal reports suggest that the adjunct use of imaging modalities can help manage cases in which molecular testing results and the clinical presentation are conflicting2. Furthermore, use of imaging modalities is suggested for the preoperative screening of emergency cases3. Lung ultrasound (LUS) is an ionizing-radiation-free, reproducible imaging modality for evaluating lung lesions, and its results are readily available, well in advance of the RT-PCR results4. However, the added benefit of LUS for managing symptomatic and asymptomatic patients with SARS-CoV-2 infection during pregnancy remains unclear. This was a retrospective cohort study conducted in two large SARS-CoV-2 pandemic hospitals in Turkey (Ankara University Hospital, Ankara, and Sancaktepe Training Hospital, Istanbul). Asymptomatic pregnant women admitted for delivery and symptomatic pregnant women evaluated for probable SARS-CoV-2 infection between May and June 2020 were included. Patients with fever, cough, shortness of breath, loss of taste or smell, or fatigue were considered symptomatic. Patients living in the same household with a person diagnosed with SARS-CoV-2 infection were considered exposed. All women were evaluated using LUS. Posterior, basal and lateral portions of the maternal lungs were examined and videoclips were stored for offline evaluation. The obstetricians performing the examinations received a brief training course on LUS and saved images were subject to quality control measures4. Two researchers (E.K., M.Y), who were blinded to the RT-PCR results of the patients, evaluated and scored the anonymized videoclips. The lung area with the highest LUS score was used for analysis (Table S1)5. The added utility of LUS to symptoms and exposure history for predicting a positive RT-PCR test result was assessed using mixed-effects binomial regression with varying intercepts. The predictive value of models with and without LUS was compared. We included 601 women in the study, of whom 82 (13.6%) had a positive RT-PCR result for SARS-CoV-2 infection. The maternal characteristics and LUS findings of both groups are presented in Table 1. The addition of LUS scoring to the baseline model consisting of symptoms, exposure history and body mass index improved significantly the prediction of a positive RT-PCR result (log-likelihood, –18.1; df, 3; P < 0.001). The additional value of LUS was weaker for asymptomatic cases (log-likelihood, –4.523; P = 0.028) in comparison to symptomatic cases (log-likelihood, −14.8; P < 0.001). In asymptomatic cases, the area under the receiver-operating-characteristics curve (AUC) improved from 0.93 (95% CI, 0.88–0.99) to 0.95 (95% CI, 0.90–1.00) with the addition of LUS scoring, albeit the change was not statistically significant (P = 0.252). In symptomatic cases, the AUC was increased significantly (P < 0.001) from 0.76 (95% CI, 0.65–0.88) to 0.93 (95% CI, 0.88–0.99) with the addition of LUS scoring (Figure 1). In symptomatic women, the positive predictive value of the model improved from 77.1% (95% CI, 67.0–84.8%) to 93.7% (95% CI, 83.7–97.8%) and the negative predictive value from 77.4% (95% CI, 62.6–87.5%) to 80.6% (95% CI, 66.0–89.9%) with the addition of LUS scoring. The LUS scoring would diagnose 24.0 (interquartile range, 18.0–30.0) additional SARS-CoV-2 infections per 100 symptomatic women compared with exposure history alone. LUS scoring could facilitate the early diagnosis of symptomatic women with probable SARS-CoV-2 infection. The projected second peak of SARS-CoV-2 pandemic is closing in and imaging modalities have proved to be very useful for managing cases during the early stages of the pandemic when availability of RT-PCR testing was limited. LUS could be useful for managing patients and rationing resources in cases in which waiting for the RT-PCR results is not an option (e.g. urgent elective procedures) or when testing capacity is strained. Strengths of our study include the use of data from two large pandemic hospitals with varying SARS-CoV-2 prevalence and the blinded assessment of LUS videoclips. Our findings are limited by the lack of external validation and the required expertise to perform the LUS assessment6. We acknowledge the work of the TUrkish Lung ultrasound In Pregnancy (TULIP) collaboration members. The full list of members who participated in this project can be found in tulipcollaboration.com and in Appendix S1. The data that support the findings of this study are available from the corresponding author upon reasonable request. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.