Quantitative CT metrics of injury patterns among WTC workers on different longitudinal FEV₁ trajectory groups

We have demonstrated diverging FEV₁ trajectories in WTC workers on longitudinal health surveillance. We performed a cohort study to investigate the association of those FEV₁ trajectories with novel QCT markers of subtle lung parenchymal injury.

We included WTC responders with CT scans with quantitative measurements (all as percentage of the CT-measured lung volume) of five different metrics: normal parenchyma (Norm%), high attenuation normal parenchyma (NormHA%), interstitial lung abnormality features (ILAV%), honeycombing pattern (HcV%), and emphysema. We used linear regression to calculate each subject's FEV₁ slope and classified them into three distinct trajectories: 1) accelerated decline (ACCEL): < -62.5 mL/year; 2) normal decline (NORM): 0 to -30 ml/year, baseline FEV₁%predicted>70% and no significant dyspnea; 3) improved: >0 mL/year.

Among 446 participants, 211 had ACCEL, 142 NORM, and 93 improved FEV₁ trajectory. On chest CTs at an average of 7.5 years after 11-September-2001 and compared to the NORM subgroup, ACCEL and improved trajectory subgroups both had less normal lung tissue (Norm%), with ACCEL having more emphysema, and improved participants higher ILAV% and NormHA%. The values of HcV% were very low and not significantly different across groups. ACCEL had a significantly higher all-cause mortality.

In this occupational cohort on longitudinal surveillance, accelerated lung function decline appears primarily associated with emphysema and airway disease, while lung function improvement is associated with subtle quantitative CT findings suggestive of interstitial inflammatory processes. The latter appeared largely nonprogressive at the time, as honeycombing was very infrequent and not different across trajectory subgroups.