Quantitative CT marker of distal airway inflammation is correlated with marker of proximal airway dysfunction in WTC workers with low FVC

<bold>Introduction:</bold> A reduced forced vital capacity (low FVC) is the most frequent spirometric abnormality in World Trade Center (WTC) responders. We previously reported (PMC7245558) quantitative chest CT (QCT) evidence of proximal (wall area percent, WAP) but not distal (ratio of expiratory to inspiratory mean lung density, MLD_EI or expiratory air trapping at -856 HU, AT_EXP856) airway inflammation in subjects with low FVC. We investigated the correlation of MLD_EI and AT_EXP856 with WAP and FVC. <bold>Methods:</bold> The study group consisted of 640 WTC responders with stable spirometry patterns, including 414 with normal spirometry, 167 with low FVC, and 59 with fixed obstruction (COPD_spiro), and QCT measurements of WAP, MLD_EI and AT_EXP856. We examined correlations globally and by spirometry pattern between quantitative chest CT measurements and spirometry measured at the closest visit date to the CT. <bold>Results:</bold> Among subjects with low FVC, there were modest correlations between MLD_EI and WAP (r=0.38, p<0.01), and pre-BD FVC (r= −0.33, p=0.03), and a strong correlation with ATEXP856 (r=0.77, p=0.0008). These correlations were not observed with AT_EXP856, or in the subgroups with normal spirometry or COPD_spiro­. <bold>Conclusion:</bold> In subjects with consistently reduced FVC, the severity of WAP and FVC abnormality correlates with that of MLD_EI, suggesting a higher likelihood of small airway dysfunction.