A careful history and physical examination are essential for patients presenting with chronic cough. Table 2 highlights the important information to obtain in the history and physical examination.
Past medical history. The past medical history is important. Prematurity and surfactant-deficient lung disease may lead to chronic lung disease in older children. Infantile eczema predisposes to other atopic disorders, such as allergic rhinitis and asthma. Recurrent right middle lobe infiltrates and atelectasis are common diagnoses in children with asthma and increased mucus production. These conditions occur because of normally poor collateral ventilation of alveoli in the right middle lobe. A nonresolving pneumonia in one lobe may be caused by a congenital lung abnormality or focal airway obstruction. Severe infections caused by Bordetella pertussis or adenovirus have been associated with the subsequent development of bronchiectasis, bronchiolitis obliterans, and chronic lung disease.
Family history. A family history of asthma significantly raises the risk of an atopic disorder in the child. Contact history of tuberculosis should be carefully sought: ask about symptoms of cough, weight loss, and night sweats among close contacts.
Social/environmental history. As noted, cough has been associated with environmental factors, so ask about exposures to potential irritants.13 Chemical irritants, such as those from marijuana and cocaine, may lead to chronic cough. Fumes from biomass combustion of wood, crop residue, and dung (common in developing countries) may contribute to chronic cough. Inner-city children may be exposed to cockroach allergens. Exposure to pet dander may induce cough from bronchoconstriction, and exposure to bird and bat droppings may cause histoplasmosis with associated cough.
The quality of cough may indicate a specific diagnosis. Table 3 presents the characteristics of classic types of cough and the probable underlying disease. Important clinical features that point to a serious underlying disease process are listed in Table 4.
Chronic cough can be associated with significant consequences; hence, each patient should be carefully evaluated. The extent of diagnostic testing should be based on the clinical setting. Adverse effects associated with tests should be carefully considered in children (eg, sedation and radiation). Table 5 provides a guide for tests in children with chronic cough based on signs and symptoms.
Chronic productive cough is always pathologic. Consider referral to a pediatric pulmonologist before embarking on potentially harmful tests.
There are only case series and cohort studies available to examine the value of available investigations for evaluation of chronic cough in children. Some of the tests that may be considered in children with chronic cough are discussed here.
Chest films. Radiographs are indicated for all children with chronic cough.14 When findings on a chest radiograph are abnormal, the odds ratio of a specific cause is 3.16 (95% confidence interval, 1.32 - 7.62).11 Bilateral diffuse peribronchial cuffing may indicate asthma, cystic fibrosis, persistent bacterial bronchitis, chronic aspiration, or primary ciliary dyskinesia. Asymmetry in aeration or vascular markings suggests the possibility of a foreign body, bronchial obstruction, vascular compression, or bronchial stenosis. Right middle lobe infiltrates are commonly seen with obstructive airway disease. Mediastinal widening may suggest hilar adenopathy and may be seen in diseases such as tuberculosis, histoplasmosis, lymphoma, and sarcoidosis.
Spirometry. This test is useful for detecting reversible airway hyperresponsiveness in children older than 6 years.15 Children as young as 3 years may also be able to participate in spirometry. It is an important tool for differentiating restrictive from obstructive diseases. Abnormalities of the inspiratory loop indicate extrathoracic obstruction.
CT scans. Chest and sinus CT scans have a role in the diagnosis of a purulent cough. They are the gold standard for examining the small airway and are more sensitive than spirometry.14 The lifetime cancer mortality risk from exposure to radiation from CT is 10 times greater for a child than for a middle-aged adult. For a single CT examination of 200 mA in a 2.5-year-old child, there is a 1 in 1000 to 2500 chance of cancer mortality.16 The use of CT for assessing small-airway and focal abnormalities has to be rationalized. It is important to consult with a pulmonologist before performing chest CT in a child to determine the goals and utility of a test that is potentially harmful.
Flexible bronchoscopy. Flexible bronchoscopy is indicated when a foreign body or an airway abnormality is suspected, when localized changes are noted on a radiologic study, for evaluation of aspiration, or when there is a need for bronchoalveolar lavage (BAL) or bronchial brushings.
Bronchoalveolar lavage. The specimen obtained with BAL is useful for microbiologic diagnostic purposes. However, the airway cellular and inflammatory profile can be used only as supportive data because adequate evidence is not available for this use of BAL in children. Cultures of BAL fluid for bacteria, viruses, and fungi are valuable for determining antimicrobial therapy.
Esophageal pH monitoring. GERD is not considered an important cause of isolated cough in a developmentally normal child; therefore, the value pH monitoring is questionable. When features suggestive of GERD are present, however, it may be useful.
Paranasal sinus imaging. When clinical features of sinusitis are present, sinus radiographs may be obtained. However, the sensitivity and specificity of these radiographs are undetermined.
Other tests. Studies have described increased airway sensitivity in different disease processes. However, the tests for airway sensitivity are not available in the clinical setting; they are available only for research purposes. The use of exhaled nitric oxide for determining the cause of chronic cough has not been studied.