TABLE 2.

PREVALENCE OF PERSISTENT WHEEZE, RECURRENT WHEEZE, AND POSITIVE ASTHMA PREDICTIVE INDEX AT AGE 36 MONTHS BY QUARTILE OF ECAT EXPOSURE

Exposure		Persistent Wheeze		Recurrent Wheeze		Asthma Predictive Index*
Quartile ECAT	Estimated ECAT (μg/m3)	% Wheeze	OR† (95% CI)	% Wheeze	OR† (95% CI)	% Positive	OR† (95% CI)
<25th percentile	≤ 0.30	9.0	1	13.5	1	12.2	1
≥25th percentile to 50th percentile	0.31–0.34	12.2	1.4 (0.7–2.9)	14.1	1.1 (0.6–2.0)	12.8	1.1 (0.5–2.1)
≥50th percentile to 75th percentile	0.35–0.40	12.8	1.5 (0.7–3.1)	16.7	1.3 (0.7–2.4)	14.1	1.2 (0.6–2.3)
≥75th percentile	≥0.41	18.6	2.3 (1.2–4.6)	21.8	1.8 (1.0–3.3)	23.1	2.2 (1.2–4.0)

Definition of abbreviations: CI = confidence interval; ECAT = elemental carbon attributable to traffic; OR = odds ratio.

^*Asthma Predictive Index: Defined as positive if the child was reported to have recurrent wheezing at age 36 months and met at least one of three major criteria (parental asthma history, allergic sensitization to more than one aeroallergen, and eczema) or two of three minor criteria (wheezing without a cold, physician-diagnosed allergic rhinitis, and allergic sensitization to milk or egg).

^†Unadjusted odds ratios.