Table 2 Relative frequency (%) by age group of observations of FEV₁/FVC below 0.70 (GOLD), below 88% predicted in women and 89% predicted in men (ERS), below 0.70 and FEV₁<80% predicted (BTS) or below the LLN

Age (y)	No of subjects			GOLD				ERS				BTS			Proposed
	No of subjects			FEV₁/FVC <0.7				FEV₁/FVC <88%pred				FEV₁/FVC<0.7 and FEV₁<80%pred			FEV₁/FVC <LLN
	Dutch	UK*	USA†	Dutch	UK*		USA†	Dutch	UK*	USA†		Dutch	UK*	USA†	Dutch	UK*	USA†
Men
16–29	110	709	804	4.6	2.1		1.4	6.4	6.6	5.0		0.9	0.7	0.5	3.6	5.4	5.4
30–39	108	675	372	9.3	2.8		2.2	8.3	5.2	4.6		0.0	0.9	0.3	6.5	5.3	4.0
40–49	58	448	211	6.9	3.4		5.7	1.7	4.7	6.6		0.0	0.4	1.0	0	4.0	6.6
50–59	28	312	96	21.4	10.3		7.3	24.3	9.0	6.3		3.6	1.9	2.1	7.1	7.1	6.3
60–69	11	213	127	45.4	17.8		16.5	18.2	12.2	4.7		9.1	3.8	2.4	9.1	6.1	4.7
⩾70	6	122	96	16.7	18.1		29.2	0.0	12.3	13.5		0.0	3.3	9.4	0.0	3.3	9.4
Total	321	2479	1706												4.4	5.3	5.5
Women
16–29	135	856	1055	0.0	0.4	0.9		5.2	11.3		5.2	0.0	0.1	0.8	5.9	5.1	4.6
30–39	195	863	1058	6.7	1.4	1.0		9.2	11.7		5.7	2.1	0.7	0.4	7.7	6.8	4.4
40–49	200	671	871	6.5	3.9	2.0		7.5	12.5		5.4	3.0	0.8	1.2	2.5	7.0	4.4
50–59	220	454	674	15.4	3.1	5.4		11.4	10.1		7.4	2.7	0.4	4.7	5.5	5.1	5.1
60–69	115	410	525	26.1	7.1	16.6		14.8	11.7		12.8	5.2	1.4	11.8	6.1	5.6	10.0
⩾70	18	302	285	5.6	13.3	21.1		0.0	16.2		13.0	0.0	6.6	10.9	0.0	8.3	9.1
Total	883	3556	4468												5.3	6.2	5.6

Data relate exclusively to asymptomatic never-smokers. Predicted values were derived from equations that fitted each data set (Falaschetti and colleagues,20 Hankinson and colleagues26 and the Dutch equations derived in this study).
*UK, data from the Health Survey for England 1995–1996. †USA, data from NHANES III.
BTS, British Thoracic Society; ERS, European Respiratory Society; FEV₁/FVC, forced expiratory volume in 1 s/forced vital capacity; GOLD, Global Initiative for Chronic Obstructive Lung Disease; LLN, lower limit of normal; NHANES III, National Health and Nutrition Examination Survey III.