Lung Elastance and Microvascularization as Quantitative Non-Invasive Biomarkers for the Aetiological Diagnosis of Lung Consolidations in Children (ELASMIC Study)

<b>Background:</b> Acute lower respiratory tract conditions are highly prevalent in paediatrics. Many of these conditions present as consolidations on imaging studies. One of the most common causes is bacterial pneumonia (BP), which requires an accurate diagnosis to implement the best treatment plan. Despite the fact that major guidelines constrain the use of invasive tests, chest X-ray (CXR) or blood tests are still routinely used for the diagnosis. In this regard, the introduction of lung ultrasound (LUS) signified an advancement in reducing the invasiveness of diagnosis. However, there are still situations where distinguishing between different aetiologies remains challenging, especially in the case of atelectasis. <b>Methods:</b> This is a prospective cohort study to assess the diagnostic accuracy of new non-invasive, quantifiable, and reproducible imaging biomarkers (lung elastance and microvascularization ratio) for differentiating BP from another major entity that causes the appearance of consolidation in imaging tests, atelectasis. It will be conducted at Sant Joan de Déu Hospital in Spain from June 2025 to June 2027. Firstly, imaging biomarkers will be measured in well-aerated lung tissue without consolidation to establish their values in healthy lung tissue, according to a predefined imaging acquisition protocol. Subsequently, the imaging biomarkers will be assessed in patients with confirmed lung consolidation by LUS (Group 1: BP; Group 2: atelectasis). <b>Results</b>: The study aims to determine whether there are statistically significant differences in the biomarker values in relation to the normal values and between the different etiological groups. <b>Conclusions</b>: The demonstration of the reliable diagnostic accuracy of these biomarkers could significantly reduce the need for invasive techniques and improve the therapeutic management of many patients with BP and other pulmonary conditions presenting with consolidation in imaging tests.