What is the appropriate laboratory workup for a patient with poorly controlled asthma?

From the Guidelines

Laboratory workup for poorly controlled asthma should include a comprehensive assessment of asthma severity and control, as well as identification of potential comorbidities and environmental triggers, to guide targeted therapy selection. The initial assessment should focus on characterizing the patient's asthma and guiding decisions for initiating therapy, including classifying asthma severity, identifying precipitating factors for episodic symptoms, and assessing comorbid conditions that may impede asthma management 1. Key components of the laboratory workup may include:

• Complete blood count with differential to assess for eosinophilia
• Serum IgE levels to identify allergic asthma and potential candidates for anti-IgE therapy
• Fractional exhaled nitric oxide (FeNO) testing to measure airway inflammation
• Sputum eosinophil count to guide therapy
• Allergy testing to identify environmental triggers
• Chest radiography to rule out alternative diagnoses or complications
• Pulmonary function tests with bronchodilator response to confirm reversible airflow obstruction Additional tests may be considered, such as alpha-1 antitrypsin levels, GERD evaluation, and CT imaging of sinuses, to further characterize the specific asthma phenotype and identify comorbidities 1. It is essential to monitor symptoms and lung function, as they represent different domains of asthma and correlate poorly over time in individual patients 1. By taking a comprehensive approach to laboratory workup, healthcare providers can develop targeted treatment plans, including inhaled corticosteroids, long-acting beta-agonists, leukotriene modifiers, or biologic agents, to improve asthma control and reduce the risk of exacerbations.

From the FDA Drug Label

The primary efficacy variable was the rate of asthma exacerbations during the 24-week, fixed steroid treatment phase An asthma exacerbation was defined as a worsening of asthma symptoms as judged clinically by the investigator, requiring doubling of the baseline inhaled corticosteroid dose for at least 3 days and/or treatment with rescue systemic (oral or IV) corticosteroids for at least 3 days.

The laboratory workup for poorly controlled asthma is not directly addressed in the provided drug label. However, the label does mention that asthma exacerbations were defined based on clinical judgment and the need for increased steroid treatment.

• The label does not provide a specific laboratory workup for poorly controlled asthma.
• It does mention that blood eosinophils and total IgE levels were measured in some trials, but it does not specify that these tests are part of a laboratory workup for poorly controlled asthma 2.

From the Research

Laboratory Workup for Poorly Controlled Asthma

• A basic diagnostic laboratory work-up is recommended for patients with poorly controlled asthma, to be modified and amplified according to individual patient needs 3.
• The laboratory work-up may include tests to identify remediable factors that are making the asthma more severe, such as chronic rhinosinusitis and gastroesophageal reflux 3.
• The Asthma Control Test (ACT) is a useful tool to help physicians identify patients with uncontrolled asthma, with a cutoff score of 19 or less providing optimum balance of sensitivity and specificity 4.
• Pulmonary function tests, such as spirometry, are essential for diagnosing asthma and monitoring its control, with reversible airway obstruction being a key characteristic of the disease 5.
• Other tests, such as peak expiratory flow (PEF) measurement, may be used to assess asthma severity and control, although diurnal variability of PEF may not always detect important changes in lung function 6.

Diagnostic Criteria

• The diagnosis of asthma requires symptoms such as wheezing, dyspnea, and cough, as well as demonstration of reversible airway obstruction using spirometry 5.
• Identifying clinically important allergen sensitivities is useful in diagnosing and managing asthma 5.
• The ACT is a reliable, valid, and responsive tool for identifying patients with poorly controlled asthma, with significant correlations between ACT scores and specialists' ratings of asthma control, as well as pulmonary function tests 4.

Management and Referral

• Patients with severe and poorly controlled asthma may require referral to an asthma specialist for consideration of additional treatment, including injectable biologic agents 5.
• Clear consensus criteria between primary health care and specialists must be determined to decide when a patient with asthma is referred from primary health care to specialist or vice versa 7.
• Incorporating questionnaires for asthma control into primary health care computer-based searches may be useful in improving the management of patients with severe and poorly controlled asthma 7.