The cost-effectiveness of chest radiography as a screening test for chronic obstructive pulmonary disease among the Bangkok elderly.

Regular screening with chest radiography (CXR) in an annual physical check up of the elderly is most frequently practiced. This study aimed to identify the CXR indices and the cost-effectiveness of CXR as a screening test for Chronic Obstructive Pulmonary Disease (COPD) among the elderly in 124 urban communities of Bangkok around Siriraj Hospital. The gold standard for diagnosing COPD followed the guidelines of the Thoracic Society of Thailand. There were 3,094 subjects who participated, completed spirometry and a CXR. The selected nine indices from PA and lateral CXR for diagnosing COPD were based on the presence of hyperinflation. The positive criteria of each index were reported. The cut-off point of best average accuracy ie, Z score of the CXR was 0.07 with a sensitivity of 75.9 per cent (95% CI 70.2-81.6%), specificity of 72.4 per cent (95% CI 70.8-74.0%) and the best average accuracy of 74.1 per cent (95% CI 72.5-75.7%) whereas the cost-effective cut-off point of a Z score of CXR as a screening test for COPD was 0.04 at the lowest grand total cost. The cost to detect one case of COPD was 2,008 baht and needed to screen 17 elderly. It is suggested that CXR is probably not a suitable screening test for COPD in the elderly due to the complicated derivation of the CXR indices. However, its efficacy may be of some value in in-office diagnosis of COPD.