Differential Diagnosis

• During presentation with acute episodic disease, the diagnosis of asthma is typically straightforward given the presence of wheezing and dyspnea. 
  • As part of the assessment, personal & family history indicative of allergic disease including eczema, urticaria, and rhinitis provides additional support. Asthma is often characterized by nocturnal awakening with wheezing and/or dyspnea. 
  • If nocturnal awakening is not present, its absence is sufficient to cast doubt concerning the asthma diagnosis. Nevertheless, other conditions may make the asthma diagnosis problematic. 
    • For example, airway obstruction caused by tumor or laryngeal edema constitute an alternative to the asthma diagnosis. However, these patients will present with stridor with harsh respiratory sounds that appear localized to particular tracheal area. That is, the more diffuse wheezing throughout the lung fields will be missing. Bronchoscopy or laryngoscopy may be required to resolve the situation. 
    • Glottic dysfunction can induce symptoms similar to asthma because these patients narrow their glottis while breathing causing occasional severe airway obstruction with periodic carbon dioxide retention. In these cases, by contrast to asthma, arterial oxygen tension is maintained. Furthermore with glottic narrowing, alveolar-arterial oxygen gradient is maintained in contrast to the alveolar-arterial oxygen gradient widening seen with lower airway obstruction (asthma). Direct examination of the patient will symptoms are present is required to establish glottic narrowing diagnosis. 
    • Alternative presentations may be seen in generalized endobronchial disease following foreign body aspiration, bronchial stenosis, or tumor presence. In these cases, persistent wheezing will tend to be quite localized in presented together with coughing paroxysms. 
    • Occasionally, acute left ventricular heart failure exhibit some signs and symptoms consistent with asthma; however, gallop rhythms, blood-tinged sputum with basilar rales allow discrimination. 
    • Bronchospasm secondary to carcinoid tumors, chronic bronchitis, and recurrent pulmonary emboli also present diagnostic alternatives. 
      • With chronic bronchitis one would not expect persistent symptom-free periods; by contrast, in asthma there should be symptoms-free periods, although with chronic bronchitis acute wheezing may occur at this is on top of persistent coughing with sputum production. 
      • On the other hand, pulmonary emboli symptoms may be quite close to those exhibited in asthma. For example, episodic breathlessness observed on exertion with wheezing may be common. Pulmonary function diagnostics also may reveal peripheral airway obstruction. Lung scans may be of normal. Differential diagnosis may be aided by patient response to bronchodilator medications and anticoagulant treatment; however, angiographic assessment would be the gold standard in establishing the definitive diagnosis.
  • Diagnosis: Asthma must be demonstrated through documentation of reversible airway obstruction in which reversibility may be defined as a 15% or greater increase in FEV1 following two puffs about beta-adrenergic agonist (e.g. terbutaline). If the initial spirometry tests are normal, increased airway reactivity may be unmasked through the use of provocative agents such as methacholine, histamine, or by forcing the patient to hyperventilate cold air.

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