Summarising published results from spirometric surveys of COPD: the problem of inconsistent definitions
OBJECTIVE: To derive adjustment factors that allow the comparison of studies using different spirometric criteria.
METHODS: Pre- and post-bronchodilator one-second forced expiratory volume (FEV1) and forced vital capacity (FVC) values were taken from the Burden of Obstructive Lung Disease (BOLD) survey in 16 centres. Using a post-bronchodilator FEV1/FVC ratio less than the lower limit of normal (LLN) as our reference prevalence, we calculated simple multiplicative adjustments to transform other reported prevalence estimates to reference values. These adjustments were then tested on independent data sets from six further BOLD centres and five centres from the PLATINO study, a Latin American survey on obstructive lung disease.
RESULTS: Prevalence estimates based on pre-bronchodilator fixed-ratio measurements were 5–25% higher than reference values, and were strongly positively biased with age and prevalence level. Applying simple adjustments provided prevalence estimates that were almost unbiased and within 5% of the reference values.
CONCLUSIONS: Using the BOLD data, we have been able to estimate COPD prevalences based on post-bronchodilator FEV1/FVC < LLN by adjusting estimates based on other common definitions, enabling more meaningful comparisons of published findings.
Document Type: Research Article
Affiliations: 1: Respiratory Epidemiology and Public Health, National Heart and Lung Institute, Imperial College, London, UK 2: Instituto Nacional de Enfermedades Respiratorias, Mexico City, Mexico 3: Woolcock Institute of Medical Research, Sydney, New South Wales, Australia 4: Kaiser-Permanente Center for Health Research, Portland, Oregon, USA 5: Post-Graduate Programme in Epidemiology, Federal University of Pelotas, Capão do Leão, Rio Grande do Sul, Brazil
Publication date: August 1, 2014
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