Table 2.

Age-sex specific and sex-specific conversion ratios to estimate the prevalence of reference Chronic Obstructive Airways (COA) disease (post-bronchodilator FEV1/FVC < Lower Limit of Normal) from two commonly presented COA prevalence estimates.

	Post-bronchodilator FEV1/FVC<LLN		Post-bronchodilator FEV1/FVC<70%		Pre-bronchodilator FEV1/FVC<70%
Age group	Male	Female	Male	Female	Male	Female
40-49 years	1	1	0.83	1.57	0.54	0.87
50-59 years	1	1	0.71	0.88	0.57	0.54
60-69 years	1	1	0.45	0.71	0.35	0.39
70+ years	1	1	0.50	0.54	0.36	0.34
40+ years	1	1	0.59	0.80	0.44	0.47

Note.

For example, to obtain the reference prevalence(post-bronchodilator FEV1/FVC<LLN) in males aged 50-59 given the prevalence in that age-sex group of COA using the definition of pre-bronchodilator FEV1/FVC<70%, multiply the given prevalence by 0.57.