Purpose of review: Asthma is defined by the 1997 National Asthma Education and Prevention Program guideline as a chronic inflammatory disorder of the airways which leads to an increase in bronchial hyperresponsiveness to a variety of stimuli or triggers. Since it is difficult to determine whether an individual patient has the above pathophysiology, particularly in young children, it is essential that clinically useful criteria be identified that can serve as proxies for the presence of asthma.
Recent findings: There are three reasons for making a diagnosis: to identify the most effective treatment to alleviate symptoms and prevent mortality; to educate the parent or primary caregiver to manage symptoms and avoid triggers; and to estimate the prognosis. A diagnostic test is a procedure which gives a rapid, convenient and inexpensive indication of whether a patient has a certain disease. The likelihood ratio incorporates both the sensitivity and specificity of the test and provides a direct estimate of how much a test result will change the odds of having a disease.
Summary: By applying the principles of evidence-based medicine to define likelihood ratios for each criterion, it should be possible to define the probability of asthma and to identify the best treatment. Future research should permit accurate correlations to be drawn between the underlying pathophysiology and the clinical condition commonly known as asthma.