Abstract

Backround: A fall in FEV₁ of ⩾10% following bronchoprovocation (eucapnic voluntary hyperventilation (EVH) or exercise) is regarded as the gold standard criterion for diagnosing exercise induced asthma (EIA) in athletes. Previous studies have suggested that mid-expiratory flow (FEF₅₀) might be used to supplement FEV₁ to improve the sensitivity and specificity of the diagnosis. A study was undertaken to investigate the response of FEF₅₀ following EVH or exercise challenges in elite athletes as an adjunct to FEV₁.

Methods: Sixty six male (36 asthmatic, 30 non-asthmatic) and 50 female (24 asthmatic, 26 non-asthmatic) elite athletes volunteered for the study. Maximal voluntary flow-volume loops were measured before and 3, 5, 10, and 15 minutes after stopping 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.

Results: There was a strong correlation between ΔFEV₁ and ΔFEF₅₀ following bronchoprovocation (r = 0.94, p = 0.000). Sixty athletes had a fall in FEV₁ of ⩾10% leading to the diagnosis of EIA. Using the FEF₅₀ criterion alone led to 21 (35%) of these asthmatic athletes receiving a false negative diagnosis. The lowest fall in FEF₅₀ in an athlete with a ⩾10% fall in FEV₁ was 14.3%. Reducing the FEF₅₀ criteria to ⩾14% led to 13 athletes receiving a false positive diagnosis. Only one athlete had a fall in FEF₅₀ of ⩾26% in the absence of a fall in FEV₁ of ⩾10% (ΔFEV₁ = 8.9%).

Conclusion: The inclusion of FEF₅₀ in the diagnosis of EIA in elite athletes reduces the sensitivity and does not enhance the sensitivity or specificity of the diagnosis. The use of FEF₅₀ alone is insufficiently sensitive to diagnose EIA reliably in elite athletes.