RESPIRATORY INVOLVEMENT IN ANKYLOSING-SPO NDYLITIS - VALUE OF EARLY LUNG-FUNCTION TESTING

In 72 males (mean age 35.1 +/- 14.4 years) evaluated 0.1 to 45 years a fter onset of ankylosing spondylitis, mean chest expansion was 5.5 +/- 2.6 cm, versus 8.7 +/- 1.2 cm (p<0.03) in 36 controls matched on age, gender, and body mass index. Chest expansion was significantly lower in patients with than without the HLA B27 antigen (p=0.02). In the pat ients, chest expansion was correlated with vital capacity (r=+0.47; p= 0.0001), total capacity (r=+0.28; p<.02), and disease duration (r=0.48 , p=0.0001). Among patients, ten had a restrictive ventilatory defect (vs 0 controls, p<0.05), eight had obstruction of small bronchi (vs 0 controls), six had obstruction of large bronchi (vs two controls), 11 had distension (vs two controls), and ten had impaired diffusion (vs f our controls); none of these differences were significant. Distension was more marked in the patients (FRC=106.9%+/-21.1%, vs 96.8%+/-18.3%; p<0.02; RV=100.7+/-30.6 vs 89.2+/-17.6; p<0.04). In the patients, dis ease duration was correlated with total capacity (r=-0.32, p=0.006) an d FEVS (r=-0.32, p=0.005). Three of the ten restrictive defects and fi ve of the ten diffusion decreases were detected within four years of d isease onset; all these patients were nonsmokers. Of the 11 distension syndromes, eight were detected within five years of disease onset; fo ur of these patients were smokers. FEVS and FEVS/VC were decreased in the 37 patients who smoked as compared with the 35 patients who did no t smoke (p<0.05 and p<0.005, respectively); in the control group, no s uch difference was found between the 13 smokers and the 23 nonsmokers. Lung function testing allows early detection of lung function impairm ent due to ankylosing spondylitis.