. 2015 Aug;7(8):1423–1440. doi: 10.3978/j.issn.2072-1439.2015.08.16

Table 1. The essential characteristics of the studies we included.

First author	Year	Ethnicity	Genotyping method	Diagnostic criteria of COPD	Resources		Sample size		Mean age		Smoking history (pack-years)		Gender distribution (male/female)		Mean FEV₁ (L)		Mean FEV₁/FVC (%)		HWE
First author	Year	Ethnicity	Genotyping method	Diagnostic criteria of COPD	Cases	Controls	Cases	Controls	Cases	Controls	Cases	Controls	Cases	Controls	Cases	Controls	Cases	Controls	HWE
Lu (22)	2004	Asian	PCR-RFLP	Guidelines of COPD diagnosis and treatment [1997]	local hospital	Healthy smokers (≥400 pack-years) with no history of COPD and a normal spirometry (age ≥50 years)	69	52	67.1±7.4	64.9±8.6	820.4±429.7	690.6±353.5	NG	NG	NG	NG	NG	NG	0.45
Huang (28)	2007	Asian	PCR-RFLP	Guidelines of COPD diagnosis and treatment [2002]	local hospital	Healthy individuals with a normal spirometry	75	69	60±6	60±6	37±4	37±4	75/0	69/0	NG	NG	60±4	86±3	0.095
Shen (25)	2010	Asian	PCR-RFLP	Guidelines of The American Thoracic	local hospital	Healthy adults with no history of COPD and spirometry show FEV₁ >85% pred and FEV₁/FVC >75%	100	100	62.3±9.7	60.9±8.6	123.5±29.7	25.6±13.3	72/28	66/34	1.28±0.43	3.57±0.65	43.5±12.8	92.8±5.8	0.12
Shen (25)	2010	Asian	PCR-RFLP	Society	local hospital		100	100	62.3±9.7	60.9±8.6	123.5±29.7	25.6±13.3	72/28	66/34	1.28±0.43	3.57±0.65	43.5±12.8	92.8±5.8	0.12
Laufs (29)	2004	Caucasian	PCR-RFLP	Guidelines of The American Thoracic	local hospital	Healthy volunteers from the same area (mostly non-smokers)	102	183	71.7	42.9	38	NG	42/60	105/78	NG	NG	NG	NG	0.84
Laufs (29)	2004	Caucasian	PCR-RFLP	Society	local hospital	Healthy volunteers from the same area (mostly non-smokers)	102	183	71.7	42.9	38	NG	42/60	105/78	NG	NG	NG	NG	0.84
Ito (24)	2004	Asian	PCR-RFLP	Guidelines of The American Thoracic	local hospital	Healthy smokers (>20 pack-years) with no history of COPD and a normal spirometry	103	88	67.4±7.8	60.8±12.0	58.3±29.1	41.1±22.2	Apr-99	72/16	1.18±0.49	2.66±0.86	45.8±10.4	80.1±7.8	0.016
Ito (24)	2004	Asian	PCR-RFLP	Society	local hospital		103	88	67.4±7.8	60.8±12.0	58.3±29.1	41.1±22.2	Apr-99	72/16	1.18±0.49	2.66±0.86	45.8±10.4	80.1±7.8	0.016
Ishii (23)	2001	Asian	PCR-RFLP	Guidelines of The American Thoracic	local hospital	Healthy, anonymous, ethnically matched volunteers	63	82	68.3±9.9	NG	102.2±40.4	NG	Mar-60	42/40	NG	NG	44.3±12.7	NG	0.31
Ishii (23)	2001	Asian	PCR-RFLP	Society	local hospital	Healthy, anonymous, ethnically matched volunteers	63	82	68.3±9.9	NG	102.2±40.4	NG	Mar-60	42/40	NG	NG	44.3±12.7	NG	0.31
Horne (27)	1990	Caucasian	Isoelectric focusing electrophoresis	Chronic bronchitis and emphysema	local hospital	local residents with similar ethnic origins	104	413	NG	NG	NG	NG	NG	NG	NG	NG	NG	NG	0.34
Wood (21)	2011	Caucasian	PCR-RFLP	FEV₁/FVC<0.7 and post-bronchodilator FEV₁<80% predicted	the UK national registry	Healthy, anonymous, geographically matched individuals	93	351	NG	NG	NG	NG	NG	NG	NG	NG	36	NG	0.45
Jung (34)	2014	Asian	PCR-RFLP	post-bronchodilator FEV₁/FVC<0.7	KOLD Cohort	Healthy smokers with a normal spirometry	203	157	67	53	46.0±23.4	30.7±17.4	199/4	148/9	1.42±0.49	3.17±0.59	47.5±10.9	78.3±5.1	0.12

COPD, chronic obstructive pulmonary disease; FEV₁, forced expiratory volume in one second; FVC, forced vital capacity; HWE, Hardy-Weinberg equilibrium; PCR-RFLP, polymerase chain reaction-restriction fragment length polymorphism; KOLD, Korean obstructive lung disease.