Background:  The proportion of lung volume with reduced attenuation at <950 Hounsfield units (LAV%) is a quantitative chest CT measurement of emphysema.  We previously showed that LAV%>2.5% was associated with accelerated FEV₁ decline in WTC responders on longitudinal health surveillance [PMC7605357].  We compared subgroups with LAV% between 2.5% and 5% and LAV%>5%, which is more often used in studies of emphysema and lung function.

Methods:  Using data from 1004 WTC responders in the WTC Chest Imaging Archive. we performed unadjusted comparisons of longitudinal FEV₁ trajectories and other characteristics among three groups defined by LAV%, as follows: <2.5%, 2.5-5%, and >5%.

Results:  Table 1 shows the main characteristics of the subjects in the three LAV% groups.  Compared with subjects in the group with LAV%>5%, those in the group with LAV% 2.5-5% had a lower rate of FEV₁ decline and a higher proportion of improved FEV₁ trajectory (p<0.05 in both instances).

Discussion: In a cohort of WTC rescue and recovery workers, subjects with LAV% 2.5%-5% have lower FEV₁ decline and a substantial proportion of subjects with improved FEV₁ trajectory, and may thus have more disease reversibility and a better prognosis.