Table 7.

Asthma age DIF analysis

Short form	Item stem	Age DIF (5–7 vs. 8–17)		Age DIF (8–12 vs. 13–17)
		X2 (df)	p	X2 (df)	P
SF	My child's asthma bothered him/her.	3.9 (5)	0.57	1.4 (5)	0.92
SF	My child had trouble breathing because of his/her asthma.	1.0 (5)	0.96	3.5 (5)	0.62
SF	My child felt wheezy because of his/her asthma.	2.6 (5)	0.77	1.8 (5)	0.88
SF	It was hard for my child to take a deep breath because of asthma.	4.2 (5)	0.53	3.8 (5)	0.58
	My child was bothered by the amount of time he/she spent wheezing.	6.4 (4)	0.17	3.0 (4)	0.57
	My child had asthma attacks.	0.8 (5)	0.98	4.1 (5)	0.53
SF	My child's chest felt tight because of asthma.	7.0 (5)	0.22	3.1 (5)	0.69
	My child's body felt bad when he/she was out of breath.	2.6 (5)	0.76	1.6 (5)	0.90
SF	My child had trouble sleeping at night because of asthma.	5.3 (5)	0.38	6.1 (5)	0.30
	My child was bothered by asthma when he/she was with friends.	0.6 (4)	0.96	3.1 (4)	0.54
	My child got tired easily because of his/her asthma.	3.6 (4)	0.46	2.0 (4)	0.73
SF	It was hard for my child to play sports or exercise because of asthma.	5.0 (5)	0.41	2.4 (5)	0.79
	My child had trouble walking because of asthma.	7.6 (4)	0.11	4.7 (4)	0.32
SF	My child felt scared that he/she might have trouble breathing because of asthma.	1.5 (5)	0.91	1.6 (5)	0.90
	My child missed school because of asthma.	9.8 (4)	0.04	3.8 (4)	0.44
	It was hard for my child to play with pets because of asthma.	3.2 (5)	0.67	5.1 (5)	0.40
	DIF items
	My child coughed because of his/her asthma. *	19.6 (5)	0.00	1.3 (5)	0.94

^*Items that exhibited statistical DIF that were retained with caution.