What Other Tests Will My Patient With Asthma Need?
This question considers 2 common scenarios in pediatric practice. The first situation involves the patient with chronic respiratory symptoms that are consistent with asthma and in whom the diagnosis needs confirmation and comorbidities assessed. The second scenario involves the ongoing follow-up of a patient with chronic asthma in whom periodic assessment and monitoring is required to be consistent with guideline-based asthma care as well as the evaluation for comorbidities should difficulties in asthma control arise. Because asthma is such a common clinical problem in pediatric practice, it is in the best interest of both the patient as well as the practitioner if a standard testing approach to or philosophy about asthma and its common comorbidities is employed. This is by no means suggesting that every patient with possible asthma be given a “rubber-stamp” evaluation, but rather that the practitioner making the assessment knows which tests to order at the appropriate time to aid in the diagnosis and management of the individual patient.
Testing will be needed based on other comorbidities that your patient may have or need to have ruled out. History and physical examination are the critical determinants of which testing will be needed and how urgently they may need to be obtained. Any red flags in the history, such as a history of severe symptoms or respiratory failure, a history suggestive of atopy or anaphylaxis, or a history of frequent infections, will suggest certain tests. As discussed below, allergy testing and immunologic testing are commonly obtained at some point in the evaluation and management of a child with asthma. Similarly, any physical examination features that are concerning or atypical for asthma will also require a prompt and thorough evaluation. Failure to thrive, clubbing, and crackles in a preschool-aged child will demand a different testing strategy than new-onset focal wheezing in an adolescent, yet both require prompt and appropriate evaluation if the diagnosis of cystic fibrosis is to be made in the first case and new-onset Hodgkin’s lymphoma in the second (Figure 43-1). The history and physical examination of the patient with respiratory symptoms is critical to track common problems and to pick up the occasional rare condition that is masquerading as asthma. However, because these things are common in medicine, testing for the patient with either established asthma or newly considered asthma is most often straightforward and non-urgent. Spirometry and chest x-ray are the most commonly obtained tests in patients with asthma and are discussed in more detail elsewhere.
Figure 43-1. Mediastinal masses are uncommon but important causes of new-onset or atypical wheezing in children and adolescents. Intrathoracic airway compression from the expanding tumor mass results in airflow obstruction and wheezing. Airway obstruction may become life-threatening. In this case, Hodgkin’s lymphoma resulted in new-onset wheezing in a 12-year-old patient.
Suffice it to say that spirometry is critical in the confirmation of airway obstruction, documenting its reversibility and severity and evaluating bronchial hyper-reactivity. Spirometry should be obtained regularly in any patient who is taking chronic medications for asthma so that management may be stepped up or down in accordance with the patient’s level of lung function and symptom control. Peak flow values alone are not sufficient to monitor pulmonary function in childhood asthma. School-aged patients can often perform accurate spirometry, but there will be some variability in the ability of individual patients, and some selectivity may be required. Any physician managing patients with asthma should identify a venue where their patients with asthma can have their lung function measured efficiently and accurately, whether this is right in your own office or in the pulmonary function testing (PFT) laboratory of the local hospital. If the local hospital is not a children’s hospital, a quick phone call to the PFT lab will confirm that the hospital does indeed test children and of what age. Other tests of lung function, such as lung volume measurements and lung diffusion, are less important in the ongoing management of asthma than is spirometry. Occasionally, a patient with asthma will require pulmonary challenge testing as part of his or her evaluation. Cardiopulmonary exercise testing can quantify the patient’s response to exercise and can help to clarify the complaints of exercise intolerance and chest pain or to assess the role of exercise-induced bronchospasm. Exercise testing can be done with concurrent flexible laryngoscopy to assess vocal cord motion during exercise when there is a question of vocal cord dysfunction. Other challenge testing may include isocapnic cold air or methacholine challenge testing to evaluate bronchial hyper-reactivity.
Radiographic studies should be tailored to the clinical question at hand. If a previous chest x-ray has been completed, any follow-up studies should address a specific question rather than be done for screening purposes. The initial chest x-ray may be normal or may demonstrate common features of asthma (Figure 43-2). Additional radiographic studies may be required from time to time. Possible scenarios include sinus imaging in patients with chronic sinus disease that is complicating asthma management and lateral neck films in patients with chronic congestion, mouth breathing, or middle ear disease.
Figure 43-2. The typical features of asthma are well-depicted on this chest radiograph of an adolescent with persistent asthma. In the AP view (A), peribronchial thickening is evident as is evidence of hyperinflation of the lungs. Hyperinflation is often best seen on the lateral chest radiograph
(B) with flattening of the diaphragms and expansion of the retrocardiac air space.
Cystic fibrosis (CF) is the most common life-shortening genetic disease in Whites. CF occurs in people of all races, however, and often presents with chronic respiratory symptoms that may be similar to asthma. Common respiratory symptoms include cough, chest congestion, with or without wheezing, and recurrent upper and lower respiratory tract infections. CF is a multisystem disease, however, and nonrespiratory complaints, particularly gastrointestinal complaints, are also common. While all 50 states now have newborn screening in place for CF, any patient with a truly chronic cough (particularly a chronic wet cough) should have a sweat test. Associated failure to thrive or persistent crackles makes this recommendation more urgent than routine. The sweat test should be done at an accredited CF care center to reduce the occurrence of either false-positive or false-negative results. Additionally, patients with clubbing, nasal polyps, or rectal prolapse also warrant a sweat test in a timely fashion. Genetic testing is also available for CF, but sweat chloride testing remains the gold standard first-line test.
Many patients with asthma also have an allergic component. This may present as allergic rhinitis, eczema, or even food allergy. The presence of food allergy is an additional risk factor for more severe asthma. While antihistamines or intranasal steroids can be trialed to control allergic symptoms, if symptoms are uncontrolled, further testing can be helpful. An elevated serum immunoglobulin-E (IgE) level or eosinophilia from a complete blood count can nonspecifically indicate an allergic disposition and correlate with risk of asthma persistence. An extremely high IgE requires further evaluation as it may suggest allergic bronchopulmonary aspergillosis or simply severe atopy. Radio-allergosorbent (RAST) testing and/or allergy skin prick testing can identify specific substances to which a patient is allergic. RAST testing is done on a blood sample, and many potential allergic triggers can be tested. Skin testing is a procedure that is performed in the physician’s (most often an allergist’s) office. While the results of allergy testing may not correlate perfectly with the clinical response of the patient, identifying potential triggers in an objective fashion with testing can certainly guide environmental control. In young children, allergy testing may be less reliable as the immune system may not be fully developed.
A patient with recurrent upper or lower respiratory tract infections may require an initial workup for immunodeficiency with serum immunoglobulins. This should be considered in patients with frequent illnesses, particularly in young children (Table 43-1). While significant immunodeficiency usually presents with recurrent invasive bacterial infections in more than one site (bacterial pneumonia and meningitis, for example) or unusual infections (such as fungal disease or Pneumocystis carinii pneumonia), it is not at all uncommon to order these studies. It is important to be aware of the development of the immune system and use age-specific normal values for immunoglobulin levels. Specific antibody titers to vaccines such as tetanus or pneumococcus can be ordered as well, as part of a more detailed evaluation. Thankfully, severe immunodeficiency disorders such as severe combined immunodeficiency and Wiskott-Aldrich syndrome are quite rare.
Evaluation of the “aerodigestive system” is often indicated in young children with chronic respiratory symptoms and asthma. Airway films, including airway fluoroscopy, can evaluate for tracheobronchomalacia, and an upper gastrointestinal series (UGI) is helpful in determining whether a vascular ring or sling may be present. Together, these studies provide a noninvasive means of detecting overt anatomic abnormalities in the airway. However, if there is adequate suspicion, further testing with either bronchoscopy or more detailed imaging may still need to be undertaken, and some patients with complex problems will require multiple studies to enable an adequate understanding of their airway anatomy and physiology. Gastroesophageal reflux is a commonly considered asthma comorbidity. If reflux is noted during the upper GI study, then this study is helpful with diagnosing reflux. However, a negative upper GI study cannot rule out reflux, as an episode may not occur during the study. This is also true for a gastric emptying scan, which may document reflux more easily because the study evolves over a more prolonged period of time. A pH study or a dual multichannel intraluminal impedance-pH monitoring is another test that is available to document reflux. With dual multichannel intraluminal impedance-pH monitoring, all reflux events are documented, both acidic and nonacidic. According to Pilic and colleagues,1 of 700 measurements using both pH and multichannel intraluminal impedance monitoring in patients ranging from age 3 weeks to 16 years, 270 measurements were abnormal, with 120 of the events abnormal only from impedance monitoring. In this study, 320 subjects tested had pulmonary symptoms. Additionally, 133 of the 320 subjects had abnormal values, and 77 of these (58%) were with impedance monitoring only. If indicated, upper GI endoscopy can be performed to evaluate for reflux or eosinophilic esophagitis.
If primary ciliary dyskinesia is suspected, due to recurrent sino-pulmonary infections or due to the presence of situs inversus, a tracheal or nasal brushing or biopsy should be obtained. The sample is examined under electron microscopy to determine whether ultrastructural abnormalities of the cilia are present. Olin and colleagues recently described an outpatient technique for obtaining a nasal scrape biopsy.2 With this technique, 88% of the samples were able to be interpreted out of 448 specimens from 107 young children (range: 0 to 5 years), 189 older children (range: 5 to 18 years), and 152 adults (older than 18 years).
Vocal cord dysfunction may co-exist with asthma as well. This condition commonly masquerades as difficult-to-treat asthma or exercise-induced asthma. It is a condition that can be difficult to diagnose, but it may be suspected when there is flattening of the inspiratory loop during spirometry. Nasolaryngoscopy may need to be performed to diagnose paradoxical vocal fold motion, and this may also be performed as part of an exercise study in the appropriate setting. Patients with vocal cord dysfunction may benefit from speech therapy to learn breathing exercises to help control future episodes.
The evaluation of a patient with asthma may need to be comprehensive if symptoms are severe and involve more than one organ system. Conversely, in a well-appearing child with typical asthma symptoms and a more benign history and physical examination, spirometry and chest radiography may be all that are required. Patients with established asthma should have regular evaluation with spirometry, and other testing should be considered if evidence of a new comorbidity arises. Testing should be sensible and streamlined to eliminate unnecessary cost and procedures, and testing should be specific to the clinical question at hand. Every patient with asthma does not need every single test, rather he or she needs those results that will guide the therapy that will contribute to the best possible outcomes.
1. Pilic D, Fröhlich T, Nöh F, et al. Detection of gastroesophageal reflux in children using combined multichannel intraluminal impedance and pH measurement: data from the German Pediatric Impedance Group [published online ahead of print October 28, 2010]. J Pediatr. doi:10.1155/2011/271404.
2. Olin JT, Burns K, Carson JL, et al. Diagnostic yield of nasal scrape biopsies in primary ciliary dyskinesia: a multicenter experience [published online ahead of print January 31, 2011]. Pediatr Pulmonol. doi: 10.1002/ppul.21402.
Heinle R, Linton A, Chidekel A. Exercise-induced vocal cord dysfunction presenting as asthma in pediatric patients: toxicity of inappropriate inhaled corticosteroids and the role of exercise laryngoscopy. Ped Asthma Allergy Immunol. 2003;16:215-225.
Lederman HM, Gelfand EW. Approach to the child with recurrent infections. In: Leung DYM, Sampson HA, Geha RS, Szefler SJ, eds. Pediatric Allergy: Principles and Practice. St. Louis, MO: Mosby; 2003.