Asthmatic elite athletes currently require evidence of asthma to obtain a therapeutic use exemption certificate, which enables them to use doses of inhaled β2 agonists in and out of competition. A fall in forced expiratory volume in 1 second (FEV1) of ⩾10% following bronchoprovocation is regarded as the gold standard for diagnosing exercise induced asthma (EIA) in athletes. Previous studies have suggested that mid‐expiratory flow—that is, forced expiratory flow at 50% of vital capacity (FEF50), might be used to supplement FEV1 to improve the sensitivity and specificity of the diagnosis.
A study involving 66 men (36 asthmatic, 30 non‐asthmatic) and 50 women (24 asthmatic, 26 non‐asthmatic) investigated these claims. Maximum voluntary flow‐volume loops were measured before and 3, 5, 10, and 15 minutes after stopping eucapnic voluntary hyperventilation (EVH) or exercise. A fall in FEV1 of ⩾10% and a fall in FEF50 of ⩾26% were used as the cut‐off criteria for identification of EIA.
Sixty athletes had a fall in FEV1 of ⩾10% leading to the diagnosis of EIA. The lowest fall in FEF50 in an athlete with a ⩾10% fall in FEV1 was 14.3%. Of the 60 athletes who were diagnosed with EIA using the International Olympic Committee's Medical Commission criteria of a ⩾10% fall in FEV1, 21 (35%) would have received a false negative diagnosis using a combination of FEV1 and FEF50 falls. The authors conclude that the inclusion of FEF50 in the diagnosis of EIA in elite athletes reduces the sensitivity of the diagnosis. The use of FEF50 alone is insufficiently sensitive to diagnose EIA reliably in elite athletes.
▴ Dickinson JW, et al. Thorax 2006;61:111–4.
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