INTRODUCTION
More than two years after the description of the first Covid-19 cases, our understanding of the clinical impact of SARS-CoV-2 on child health is significantly improved. Overall, Covid-19 has caused much higher morbidity and mortality on adults compared with children, although hospitalizations, severe disease and deaths have been recorded in any age, including in the youngest children.1,2 Moreover, children have also suffered from post-acute complications of SARS-CoV-2 infection, including the Multisystem Inflammatory Syndrome and Long Covid.3-6
The recognition that the large majority of children infected with SARS-CoV-2 develop only mild symptoms and spontaneously completely recover poses the challenge to understand the optimal way to specifically evaluateinfected children, rather than simply translating adult practice into pediatrics. For example, symptomatic adults assessed in the emergency department (ED) frequently undergo laboratory diagnostics and imaging, including chest X-Ray or Computed Tomography.7 This approach was usually routine practice in the pre-vaccine era, when the clinical impact of Covid-19 on adults has been massive, and is now mostly reserved to symptomatic patients. In children, such an approach does not seem justified. As most children have a low risk of develop severe disease and vaccinations further reduce this risk, an approach based on routine traditional imaging does not seem justified, as it is associated with radiation exposure and longer waiting times in the pediatric emergency department (PED).1
In this context, an approach based on safe and rapid point-of-care tools to evaluate a child with SARS-CoV-2 infection seems to be more appropriate. As Covid-19 pneumonia mainly affects the peripheral areas of the lungs, early preliminary studies in both adults and children have documented that Lung Ultrasound (LUS) can easily detect low respiratory tract infection (LRTI) during SARS-CoV-2.8 However, while several adult studies on large cohorts have documented also a prognostic role of LUS in predicting hospitalizations and severe outcomes in infected adults, pediatric studies have provided less conclusive information, as they mostly included a small number of patients from single centers and without enough patients with moderate/severe disease. 9-18For these reasons, we performed this multicenter national study in order to better characterize the clinical and prognostic role of LUS in children with Covid-19 assessed in the PED.