FIGURE 1.

A summary of the place of spirometry in diagnostic algorithms from current guidelines. BTS: British Thoracic Society; SIGN: Scottish Intercollegiate Guidelines Network; NICE: National Institute for Health and Care Excellence; GINA: Global Initiative for Asthma; ERS: European Respiratory Society; FEV₁: forced expiratory volume in 1 s; FVC: forced vital capacity; LLN: lower limit of normal; F_ENO: fractional exhaled nitric oxide; BDR: bronchodilator responsiveness; PEF: peak expiratory flow; ⊕: positive; ⊝: negative. ^#: BTS/SIGN uses high probability/intermediate/low probabilities of asthma as part of the diagnostic algorithm. A patient in the high-probability category has an increased probability of having asthma if spirometry shows airflow obstruction reversible to bronchodilator; a child who is in the intermediate category can have asthma diagnosis confirmed if spirometry is abnormal and has significant responsiveness to bronchodilator; ^¶: direct challenge tests (methacholine challenge test positive if provocative concentration causing a 20% fall in FEV₁ ≤8 mg·mL⁻¹; mannitol test positive if fall in FEV₁ ≥15% at cumulative dose of ≤635 mg), indirect challenge test (exercise challenge positive range: 8–20% fall in FEV­₁); ⁺: indicated for children with severe disease or clinical suspicion of other conditions; ^§: GINA guideline provides two options in case the patient is on controller treatment and requires asthma diagnosis confirmation: in case there are variable respiratory symptoms but spirometry is normal, the recommendation is to consider repeating spirometry either when withholding bronchodilator or the patient is symptomatic. In case there are lesser respiratory symptoms and spirometry is normal, bronchodilator testing can be repeated when symptomatic or when temporarily stopping bronchodilator; ^ƒ: direct bronchial challenge test with methacholine or indirect bronchial challenge tests by using either a treadmill, bike or both; ^##: PEF variability would be an inferior choice to challenge tests and could be used if challenge tests are not available.