<unk>  can be difficult to diagnose clinically given the lack of specific symptoms and frequent misinterpretation as manifestations of vigorous<unk> . There are many mimics that present with similar symptoms, such as vocal cord dysfunction, cardiac arrhythmias, cardiomyopathies, and gastroesophageal reflux disease. It is also important to distinguish those who have asthma with<unk>  worsening, and who consequently will have abnormal testing at rest, from true<unk> , where there will be normal baseline results. Because of the wide differential diagnosis of exertional respiratory complaints, the diagnosis of<unk>  based on history and self-reported symptoms alone has been shown to be inaccurate and will result in an incorrect diagnosis more than 50% of the time. An important and often over-looked differential diagnosis is<unk><unk>  laryngeal obstruction EILO. The latter can co-exist with<unk>  and is best differentiated using objective testing and continuous laryngoscopy during<unk>  (CLE) testing. Spirometry Objective testing should begin with spirometry at rest. In true<unk> , the results should be within normal limits. Should resting values be abnormal, then asthma, or some other chronic lung condition, is present. There is, of course, no reason why asthma and<unk>  should not co-exist but the distinction is important because without successful treatment of underlying asthma, treatment of an<unk>  component will likely be unsuccessful. If baseline testing is normal, some form of<unk>  or pharmacologic stress will be required, either on the sideline or practice venue, or in the laboratory.<unk>  testing Treadmill or ergometer-based testing in lung function laboratories are effective methods for diagnosing<unk> , but may result in false negatives if the<unk>  stimulus is not intense enough. Field-exercise challenge Field-exercise challenge tests that involve the athlete performing the sport in which they are normally involved and assessing FEV1 after<unk>  are helpful if abnormal but have been shown to be less sensitive than eucapnic voluntary hyperventilation. Eucapnic voluntary hyperventilation challenge The International Olympic Committee recommends the eucapnic voluntary hyperventilation (EVH) challenge as the test to document<unk><unk>  asthma in Olympic athletes. In the EVH challenge, the patient voluntarily, without<unk> ng, rapidly breathes dry air enriched with 5% for six minutes. The presence of the enriched compensates for the losses in the expired air, not matched by metabolic production, that occurs during hyperventilation, and so maintains levels at normal. Medication challenge Medication challenge tests, such as the methacholine challenge test, have a lower sensitivity for detection of<unk>  in athletes and are also not a recommended first-line approach in the evaluation of<unk><unk>  asthma. Mannitol inhalation has been recently approved for use in the United States. A relatively recent review of the literature has concluded that there is currently insufficient available evidence to conclude that either mannitol inhalation or eucapnic voluntary hyperventilation are suitable alternatives to<unk>  challenge testing to detect<unk>  and that additional research is required.
Exercise-induced bronchoconstriction
Bronchial hyperresponsiveness
Reactive airway disease
Hypoxic pulmonary vasoconstriction
Central neurogenic hyperventilation
Cholinergic urticaria
Coronary vasospasm
Mediastinal fibrosis