TABLE 5.

Association between symptoms experienced during methacholine testing and the result of methacholine testing

Symptom	Predictive value, %		P
	Positive	Negative
Dyspnea (n=227)
PC20<2 mg/mL	13.2	90.2	0.30
PC20<8 mg/mL	32.2	78.0	0.02
PC20≤16 mg/mL	50.7	65.3	0.001
Cough (n=232)
PC20<2 mg/mL	11.2	87.5	0.69
PC20<8 mg/mL	27.6	72.0	0.93
PC20≤16 mg/mL	47.4	61.3	0.08
Wheezing (n=121)
PC20<2 mg/mL	14.9	89.6	0.20
PC20<8 mg/mL	32.2	74.2	0.19
PC20≤16 mg/mL	52.9	60.2	0.02
Chest tightness (n=185)
PC20<2 mg/mL	15.1	91.2	0.05
PC20<8 mg/mL	31.4	75.3	0.14
PC20≤16 mg/mL	51.4	62.8	0.004

PC₂₀ Provocative concentration of methacholine causing a 20% fall in forced expiratory volume in 1 s