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

INTRODUCTION

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.