To the Editor:
I read with great attention the paper by Saldana and colleagues entitled “Association of Computed Tomography Densitometry with Disease Severity, Functional Decline, and Survival in SSc-ILD” (1). The study is very interesting because it further explores chest quantitative computed tomographic (QCT) imaging possibilities in to stratifying patients with systemic sclerosis (SSc) according to severity to establish the prognosis. As the authors point out, many of the elements useful for establishing the SSc–interstitial lung disease (ILD) prognosis (i.e., forced vital capacity, diffusing capacity of the lung for carbon monoxide, and fibrosis visual score) are subject to significant variability, whereas QCT imaging is operator independent (2).
Conversely, the paper indirectly leads to considering some issues as relevant limitations for QCT imaging implementation in trial or clinical practice. For example, patients with emphysema were excluded. However observational data suggest that in the SSc, emphysema is associated with ILD, appearing as a combined pulmonary fibrosis and emphysema syndrome (3). Having excluded these patients who have a poor prognosis could have depleted the cohort of patients at a high risk of mortality (4). A second limitation that Saldana and colleagues report is the scarce possibility of using QCT in clinical routine for the following two reasons: inability to process computed tomographic (CT) scans of all patients (38% of all CT scans performed) and the significant time required to evaluate each CT scan. Fortunately, these two issues can be overcome, as already described in the literature, by using an independent operator algorithm based on a free and open-source program that provides QCT indexes in a few seconds (5).
For this reason, we urge the authors to look with more optimism at their results, which support the possibility of easily establishing SSc-ILD prognosis, providing rheumatologists with new tools for tailoring treatments (in particular antifibrotics).
Footnotes
Author disclosures are available with the text of this letter at www.atsjournals.org.
References
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