LEICESTER – Asthma has traditionally been viewed as a series of reversible episodes of bronchoconstriction. Newer radiological visualisation techniques however, show that severe asthma patients at least often present irreversible radiological findings such as bronchial wall thickening. A new study has found that, out of a group of severe asthmatics examined by high-resolution CT (HRCT), only 20% had normal results.
“Approximately 5% to10% of asthma patients have severe and/or difficult-to-treat asthma. These patients with inadequately controlled severe asthma are at a particularly high risk of exacerbations, hospitalisation and death, and often have a severely impaired quality of life“ write Dr Sumit Gupta and his colleagues of the Institute for Lung Health, University of Leicester, UK, in the journal Chest.
The detection of bronchial wall changes is important in patients with severe asthma as this may impact the management strategy. High-resolution CT (HRCT) scanning, a useful tool to noninvasively assess airway wall changes in patients with asthma, is part of the diagnostic workup of severe asthma, but its application varies between centres.
Data from the retrospective study of 185 patients with severe asthma treated at the Difficult Asthma Clinic (DAC) in the UK showed that HRCT scan abnormalities were present in 80% of subjects: 62% had bronchial wall thickening, 40% had bronchiectasis and 8% had emphysema, with many patients showing features of multiple pathologies.
“We have demonstrated that there is a high prevalence of bronchiectasis and bronchial wall thickening in the population of patients with severe asthma” write the study’s authors.
Most patients with severe asthma not only have CT scan abnormalities but the findings on high-resolution CT scans correlate poorly with clinical findings. “The most common indication for performing a high resolution CT scan in our study had been a clinical suspicion of bronchiectasis, but this had only a 74% sensitivity and a 45% specificity.”
The FEV1/FVC ratio could possibly serve as a better indicator of the likelihood that abnormalities will be found on HRCT.
“Nonradiologic assessments fail to reliably predict important bronchial wall changes; therefore, to define fully the prevalence of CT scan abnormalities, CT scanning will need to be undertaken in all patients with severe asthma,” they conclude.
Gupta S et al.: Chest. 2009 Dec;136(6):1521-1528
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