TABLE 1

Sensitivity and specificity of different spirometry indexes for an asthma diagnosis

Index and threshold	Sensitivity (%)	Specificity (%)	Positive predictive value (%)	Negative predictive value (%)	Ref.
FEV₁
<80% predicted	22	95	46	87	[20]
<91% predicted	43	77	26	88	[20]
≤0.8 z-scores	44	77	83	35	[12]^#
FEV₁/FVC
<70% predicted	52	73	75	49	[11]
<80% predicted	12–52	72–93	Not applicable	Not applicable	[12]
<LLN	15	97	48	86	[20]
BDR
10%	58	60	81	33	[21]
12%	35–36	90–98	Not applicable	Not applicable	[12]
PEF variability 12%	50	72	48	74	[11]

FEV₁: forced expiratory volume in 1 s; FVC: forced vital capacity; LLN: lower limit of normal; BDR: bronchodilator response; PEF: peak expiratory flow. ^#: original source of data cited in the European Respiratory Society task force report was [14].