CRYPTOGENIC FIBROSING ALVEOLITIS AND THE FIBROSING ALVEOLITIS OF SYSTEMIC-SCLEROSIS - MORPHOLOGICAL DIFFERENCES ON COMPUTED TOMOGRAPHIC SCANS

Background - The purpose of this study was to identify morphological d ifferences on the computed tomographic (CT) scan between cryptogenic f ibrosing alveolitis (CFA) and the fibrosing alveolitis associated with systemic sclerosis (FASSc), and to examine their biological relevance . Methods - One hundred and seven patients with CFA (n=55) or FASSc (n =52) who had undergone thin section CT scanning were included. Multiva riate analysis was used to identify morphological differences on the C T scans between lone CFA and FASSc, and to determine whether the patte rn and distribution of disease on the CT scans were functionally signi ficant (as judged by the lung transfer factor (TLCO), forced vital cap acity (FVC), and arterial oxygen tension (Pao(2))) or predictive of su rvival (independent of the type and extent of fibrosing alveolitis, ag e, sex, and smoking history). Results - Increasingly extensive disease on CT scans was associated with a coarser reticular pattern (increase in reticular score per percentage increase in disease extent=0.06, 95 % confidence interval (CI) 0.03 to 0.09, p <0.0005) and increasing upp er zone involvement (increase in ratio of upper zone to total disease per percentage increase in disease extent=0.002, 95% CI 0.000 to 0.003 , p <0.04). Patients with CFA were characterised by a higher upper zon e ratio (difference=0.08, 95% CI 0.02 to 0.13, p <0.004) and a weak tr end towards a coarser reticular pattern (p=0.09), independent of disea se extent. Smokers with CFA had more upper zone involvement (differenc e=0.11, 95% CI 0.05 to 0.16, p <0.0005) and a coarser reticular patter n (difference in reticular score= 1.92, 95% CI 0.27 to 3.55, p <0.02) than smokers with FASSc. The extent of disease on the CT scan was pred ictive of lung function impairment and survival but the pattern and di stribution of disease were not. Conclusions - Patients with CFA have r elatively more upper zone involvement than those with FASSc independen t of the extent of disease on the CT scan. This finding may result fro m smoking related damage but is not functionally significant.