Background Decreased chest expansion is a time honoured sign in patients with ankylosing spondylitis (AS). However, the clinical usefulness of this measurement and the frequency with which it is used remains largely unknown.
Objectives We studied: 1) the frequency of its clinical use among rheumatologists and 2) its inter and intra-observer variation along with its sensitivity and specificity among a group of patients with AS and suitable controls.
A total of 300 rheumatologists in the United States and in Europe were contacted by e-mail. The frequency they measured chest expansion in their daily practices and the characteristics of their patients they performed the test on, were inquired.
Thirty patients with AS, 36 with rheumatoid arthritis (RA), 31 with systemic lupus erythematosus (SLE) who were regularly followed in the Rheumatology Department of Cerrahpasa Medical Faculty and 76 healthy controls (HC) who consisted of healthy hospital staff were recruited. Chest expansion was measured at the 4th intercostal space by two independent observers in the morning (between 8–10 AM) in the afternoon (between 2–4 PM) and one week after the initial determinations. The relationship between the chest expansion and gender, age and vital capacity (VC), body mass index (BMI) were determined in all the patients and controls.
Results Eighty-two (27%) of the 300 rheumatologists responded. Three of the responders (4%) stated that they measured chest expansion in every patient whereas 72 (87%) said that they performed the test only in patients suspected to have ankylosing spondylitis. Seven rheumatologists (9%) reported that they never measured chest expansion.
There was a good intra and inter-observer agreement in chest expansion measurements as judged by a difference of less than 1 cm in 80% of the calculations. A chest expansion of less than 2.5 cm had a sensitivity of 23% in patients with AS whereas it had a specificity of 49% (2 patients with RA, 1 with SLE and 5 HC had values below 2.5 cm). There was a significant correlation between vital capacity and chest expansion only in male patients with AS (r = 0.51, p = 0.005). Chest expansion decreased with age in all groups (r2 = 0.083, F = 0.0001). There was no relationship between the chest expansion either with gender or with BMI, both among the patients and the controls.
Conclusion Most of the rheumatologists measure chest expansion only in patients suspected to have AS. It is a test that has good intra and inter-observer reliability. However it has a limited sensitivity and specificity in AS and its value in differential diagnosis is limited.
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