Table 2. Variables and point values used for the model.

Factors	Variables	Points
Living environment	×1*	Urban =0, rural area =1
Gender	×2*	Male =1, female =0
Age	×3*	Years
Educational level	×4	No =0, primary school =1, Junior school =2, high school =3, college =4, graduate =5
Dyspnoea	×5*	Only get breathless with strenuous exercise =1; Get short of breath when hurrying on the level or up a slight hill =2; Walk slower than people of the same age on the level because of breathlessness or have to stop for breath when walking at one’s own pace on the level =3; Stop for breath after walking 100 yards or after a few minutes on the level = 4; Too breathless to leave the house =5
Cooking fuels	×6	No =0, electricity =1, gas =2, coal =3, biomass fuel =4
Smoking index	×7*	Number of packs/day*years
Occupational exposure	×8*	Years
Family history	×9	No =0, one person =1, two persons or more =2
Childhood infection history	×10	No =0, one infection =1, two infections =2, three infections =3
Body mass index	×11*	Weight(kg)/body height(meter)square kg/m2
Cough	×12*	Cough for more than two years & over three months/year no =0 yes = years
Sputum	×13	Cough with production for more than two years & over three months/year no =0 yes = years
Wheezing	×14*	No =0, yes =1

*These statistically significant variables were incorporated into the final function model by stepwise discriminant analysis.