LUS for COVID‐19 Pneumonia: Flexible or Reproducible Approach?

To the Editor: We read with great interest the reply by Ma IWY and co‐workers ¹ to our letter. ² In their consensus‐based recommendations, ³ authors preferred to promote a flexible rather than a prescriptive approach on how LUS should be performed in the case of COVID‐19 patients. We raised a concern on the statement that currently there are no data to support the use of one protocol over another. Instead, our protocol has been validated both in relation to other acquisition protocols and for its prognostic value. ⁴

In their reply, the authors, while recognizing the value of our conclusions, defended their positions not endorsing a single protocol over others, preferring a flexible approach on LUS acquisition data from patients. ¹ The main reason to choose this approach instead of a rigorous one is to adapt acquisition scans not to answer only focused questions. This can give an advantage in order to perform a more extensive evaluation for patients with comorbidities (pulmonary edema, fibrosis), particular clinical conditions, or with limitations to be placed in peculiar positions. Moreover, patients' disposition decisions cannot be made solely on LUS findings. ¹

Although these considerations can be considered fully sharable, some issues deserve to be discussed.

We need to distinguish between LUS approaches that can support physicians in reaching a diagnosis from a LUS protocol useful to stratify a target pathology such as COVID‐19 pneumonia.

The first considers LUS for respiratory patients as an extension of the medical semiotic. We totally agree, in that context, with the authors. A more extensive LUS examination, integrating data from different organs and anatomic districts, medical history, classic semiotic maneuvers has to become the most correct approach to patients. Actually, ultrasonography is an amplifier of signs, which could not be gathered or cannot be easily detected with classic semiotics. It allows often detecting an incidental and unexpected finding, a small detail, which changes the diagnostic pathway. It is able to improve the accuracy of diagnosis, enhance physician–patient interaction, optimize, limit or justify other diagnostic techniques, and guide interventional procedures or therapeutic choices. Our group published a dedicated article related to this interesting topic. ⁵

The second represents an attempt to give rules to physicians performing LUS evaluations in patients with COVID‐19 pneumonia.

Our validated protocol tried early, and for the first time in this pandemic, to standardize LUS imaging settings, acquisition anatomic‐landmarks, and LUS scoring system. ⁴ Afterward, this approach was compared to other acquisition protocols, and its prognostic role was validated. ⁶ , ⁷ , ⁸ The final goal of our work was to provide shared rules to physicians in order to speak the same language regarding the use of LUS in COVID‐19 pneumonia. This is crucial to allow the development of scientific knowledge in a new context such as this pandemic.

Similar to other imaging techniques (Chest‐X‐rays and CT scans), in which both the acquisition and the reading protocol are standardized, at least for specific organs and pathologies as well, a standardized protocol for LUS improves accuracy and reproducibility. From this point of view, promoting a flexible approach can lead to increasing confusion especially when discussing observations related to ultrasound artifacts. Moreover, a rigorous approach can limit the multiplication in the literature of works addressing “fanciful signs”, which often refer to the same imaging pattern. Indeed, only by focusing on the links between the underlying physical phenomena, the anatomy, the image formation processes, and the LUS patterns of interest, it will be possible to develop a solid and reliable methodology. ⁹ , ¹⁰ , ¹¹