High-resolution CT pulmonary findings in idiopathic ankylosing spondylitis: correlations with clinical assessment, plain chest X-ray and pulmonary function tests

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Aim: The aim of this study is to evaluate pulmonary manifestations of ankylosing spondylitis on high-resolution computed tomography (CT) scan and to correlate these findings with clinical assessment, plain chest X-ray and pulmonary function tests. Methods: The study comprised 32 patients (26 males [81.3%], 6 females [18.8%]) who met the modified New York criteria for diagnosis of idiopathic ankylosing spondylitis; in addition 10 normal subjects not complaining of any respiratory symptoms and matched for age and sex served as a control group. All patients were subjected to full history-taking, full clinical examination, chest X-ray, high-resolution computed tomography (HRCT) chest and pulmonary function tests. Results: The abnormalities on HRCT included evidence of apical lung fibrosis in two patients (6.3%), interstitial lung disease in six (18.8%), minor interstitial abnormalities in eight (25%), bronchiectasis in four (12.5%), lung nodules in three (6.3%) and pleural thickening in five patients (6.3%). Nine patients (28.1%) showed negative findings by chest X-ray which revealed positive findings on HRCT. Five patients (15.6%) showed positive findings on both HRCT and plain chest X-ray, and 18 patients (56.3%) showed no findings on both HRCT and chest X-ray. Four patients (12.5%) showed normal pulmonary function tests, 25 (78.13%) showed restrictive pattern, 17 (53.13%) had obstructive pattern and 26 patients (81.3%) had diffusion defects. Conclsuion: The identification of non-apical minor basal interstitial lung disease in our study which was previously reported in other studies, raises a possible association to ankylosing spondylitis. High-resolution CT scan is more sensitive than chest X-rays in detection of such minor interstitial lung disease (ILD), and other parenchymal lung changes.