DIAGNOSIS 2 Definition of asthma 3 Definition The

DIAGNOSIS 2

Definition of asthma 3

Definition The guidelines define asthma as: a chronic inflammatory disease of the airways many cells play a role (mast cells, eosinophils, and T lymphocytes)

Definition recurrent episodes of: • Wheezing • Breathlessness • chest tightness • Cough particularly at night and/or in the early morning

Definition widespread but variable airflow limitation at least partially reversible either spontaneously or with treatment

Definition increase in airway hyperresponsiveness to a variety of stimuli

Definition • Chronic Inflammation • Bronchial Hyperresponsivenes s • Reversible Airway Obstruction

Confirmation of the diagnosis of asthma is based on two key elements:

The history or presence of respiratory symptoms consistent with asthma The demonstration of variable expiratory airflow obstruction

The variation in expiratory airflow may be demonstrated with measurements made at different points in time

The variation in expiratory airflow or in response to administration of anti-asthmatic therapy

The diagnosis of asthma can be confirmed using several approaches depending on the patient's clinical presentation and clinical course

Diagnosis with pulmonary function testing

The 2007 asthma guidelines of the National Asthma Education and Prevention Program (NAEPP) recommend that spirometry, before and after administration of a bronchodilator be performed in all adolescents and adults in whom the diagnosis of asthma is being considered

The use of spirometry or bronchoprovocation testing to demonstrate reversible airflow obstruction is particularly important when the patient's symptoms or response to therapy are not typical

Use of pulmonary function testing in this manner helps to prevent both over- and under-diagnosis of asthma

As examples persons without asthma may have recurrent cough and chest congestion due to repeated bouts of bronchitis, episodic chest heaviness due to gastroesophageal reflux, or chronic cough due to post-nasal drip syndrome

In each of these conditions repeatedly normal spirometry or peak flow measurements would help to exclude the diagnosis of asthma.

Conversely reversible airflow obstruction in the patient with chronic cough but without other chest symptoms or wheezing on examination could assist in making the correct diagnosis of asthma

Diagnosis when initial PFTs are normal

Patients with asthma may have normal lung function at the time of evaluation. If the diagnosis is not apparent based on history alone then the following strategies are useful:

Repeat evaluation by the clinician when the patient is symptomatic Repeated patient-based measurements of PEFR over time, possibly with a therapeutic trial of bronchodilator Bronchoprovocative testing, such as with a methacholine or exercise challenge

Serial measurements of lung function over time

As previously noted, asthma is characterized by variable expiratory airflow obstruction. Normal individuals without asthma experience little variability (less than 20 percent) even when respiratory symptoms are present.

One useful strategy to diagnose asthma in patients with normal lung function at their medical visit is to provide them with a handheld peak flow meter for home use and ask that they keep a diary of their peak flow recordings, as described previously.

The diagnosis of asthma is confirmed by a reliable series of recordings that document more than 20 percent variability in PEFR over time (especially when PEFR reductions are associated with asthmatic symptoms)

Similar data collection can take place in the clinician's office by recording PEFR or spirometry at each patient visit. This method is less dependent on the reliability of the patient independently making selfmeasurements, although multiple visits may be required

Serial patient-recorded measurements of PEFR over time can be combined with a "therapeutic trial" of a bronchodilator.

Significant decreases in PEFR that reverse within minutes of use of an inhaled beta-adrenergic agonist typify asthma.

In individuals without asthma the increase in PEFR following bronchodilator administration would be expected to be less than 20 percent

Bronchoprovocation

Bronchoprovocation testing 33

the diagnosis of asthma can be confirmed with bronchoprovocation testing, usually in the form of methacholine challenge.

A provocative stimulus “direct” • methacholine and histamine “indirect” exercise, eucapnic voluntary hyperventilation, cold air hyperventilation, hypertonic saline, mannitol, adenosine monophosphate [AMP] 35

This diagnostic strategy is particularly useful for patients with atypical symptoms such as isolated chronic cough.

Standardized protocols for methacholine testing The test consists of performing spirometry at baseline and then after each dose of nebulized methacholine 37

Diagnosis based on history and clinical course

In some instances, the diagnosis is clear because of a characteristic history and clinical course.

As an example the diagnosis is readily made in a patient who describes repeated episodes over time of typical symptoms triggered by typical stimuli (especially allergic triggers) and responding to antiasthmatic medications.

in patients presenting to an urgent care setting or emergency department the diagnosis can be rapidly made when asthmatic symptoms and musical wheezes on auscultation resolve over the course of minutes to hours in response to bronchodilators and glucocorticoids

If spirometry is not available, a diagnosis of probable asthma can be made based upon history and response to therapy alone among patients with classic symptoms who respond promptly and completely to therapy.

In patients with less typical or persistent symptoms, further evaluation and a more formal approach to diagnosis is indicated

INDICATIONS FOR REFERRAL

Consultation with an asthma specialist, either a pulmonologist or an allergist is warranted when the diagnosis of asthma is uncertain, when the asthma is difficult to control, or when a patient has frequent exacerbations