Nevertheless, the lack of correlation between MEF25 aiid FVC or TLC in these patients does not support this concept. Moreover, the lack of any difference in the mean age, disease duration and form, pulmonary symptoms, and/or roentgenologic abnormalities and positive serologic features between our abnormal lung function patients with and without SAD (Table 4) indicates that the presence of SAD is not strictly related to the severity of the pulmonary disease. In addition, the observed difference in Deo between the SAD-positive and SAD-negative patients does not indicate difference in the severity of pulmonary involvement, since lung restriction, which is related to the worst prognosis, was not different between them as suggested by the FVC and TLC values (Table 5).
The low prevalence of SAD that we found is not in agreement with the reports by others. Guttadauria et al found 42 percent prevalence of SAD and 27 percent of obstructive disease in 45 studied patients with scleroderma. The most frequent abnormality they found was elevated RV in 33 patients, while RV/TLC was high in 21 patients. They considered as evidence of SAD an elevated RV in patients with no reduced lung volumes and supported that this is a common and early finding in scleroderma. However, it should be noted that high RV may be due to some other cause, such as the involvement of chest wall or diaphragm in patients with scleroderma. It is also noteworthy that expiratory flow rates were normal in 15 of 19 patients considered to have SAD, while 10 of them were smokers.