Table 1.

Recruitment of the study population

	Cases		Controls
	N	%	N	%
Patients contacted	424	100	749	100
Not eligible	133	100	249	100
Moved from urban to rural area or vice versa	62	46.6	143	57.4
Without parent/legal guardian	19	14.3	33	13.3
Place of living outside Valdivia regiona	16	12.0	40	16.1
Asthma diagnosis not confirmed by a physician	29	21.8	NA	NA
Not born in Chile	1	0.8	3	1.2
Mentally/physically disabled	4	3.0	2	0.8
Control patient reporting diagnosis of asthma	NA	NA	24	9.6
Other	2	1.5	4	1.6
Eligible study population	291	100	500	100
Non-responder	53	100	173	100
No interest	21	39.6	90	52.0
No time	22	41.5	58	33.5
General doubts	9	17.0	12	6.9
Other	1	1.9	13	7.5
- Study population with complete interview and SPT data	188	100	294	100
Participation in additional study parts:
Stool samples	138	73.4	137	46.6
Blood samples	163	86.7	245	83.3
Dust samplesb	112	59.6	188	63.9

NA indicates not applicable

^a Indicating that people lived more than 100 km away from Valdivia

^b Dust samples from home visits