Table 3

Test qualities of different ways of expressing a positive bronchodilator response with PEF measurements (ΔPEF absolute with cut off values of 40, 60, and 80 l/min and ΔPEF % baseline with cut off values of 10%, 15%, and 20%) in relation to different references as assessed by spirometric tests (n = 240)

Δ PEF measurements	Sensitivity	Specificity	PPV	NPV
(A) ΔFEV₁ ⩾9% predicted
⩾10% baseline	56	85	36	93
⩾15% baseline	44	94	52	92
⩾20% baseline	25	98	67	90
⩾40 l/min	53	87	39	92
⩾60 l/min	28	95	45	90
⩾80 l/min	13	99	57	88

(B) ΔFEV₁⩾200 ml absolute
⩾10% baseline	41	86	52	81
⩾15% baseline	27	94	63	78
⩾20% baseline	16	99	83	77
⩾40 l/min	35	88	50	79
⩾60 l/min	18	95	55	76
⩾80 l/min	6	98	57	75

(C) ΔFEV₁⩾12% predicted and 200 ml absolute
⩾10% baseline	73	82	16	98
⩾15% baseline	42	93	37	93
⩾20% baseline	29	98	58	93
⩾40 l/min	64	84	16	98
⩾60 l/min	36	93	20	97
⩾80 l/min	9	97	14	96

(D) ΔFEV₁⩾15% baseline and 200 ml
⩾10%baseline	60	82	18	97
⩾15% baseline	47	91	26	96
⩾20% baseline	40	97	50	96
⩾40 l/min	53	84	18	96
⩾60 l/min	27	93	20	95
⩾80 l/min	7	97	14	94

PPV = positive predictive value; NPV = negative predictive value.