The most appropriate diagnostic test to perform next is high-resolution CT (HRCT). This patient most likely has bronchiectasis. Symptoms of bronchiectasis include chronic cough with purulent sputum and recurrent pneumonia (in both smokers and nonsmokers). Pulmonary function tests commonly detect mild to moderate airflow obstruction, which may overlap with other disease findings (such as COPD). Physical examination findings may include crackles and/or wheezing on lung auscultation. This patient has a history of pertussis as a child, has a chronic cough with mucopurulent sputum, and has increased bronchovascular markings on chest radiograph. The cause of bronchiectasis in this patient may be lung damage associated with her history of pertussis. In most patients with bronchiectasis, the chest radiograph shows nondiagnostic radiologic findings, including linear atelectasis or dilated and thickened airways (“tram” or “parallel” lines). HRCT is the gold standard diagnostic test for parenchymal lung disease, such as bronchiectasis, and should be performed in this patient. Contrast enhancement is not necessary. Airway dilatation with lack of tapering, bronchial wall thickening, and cysts may be seen on HRCT. After the diagnosis is confirmed, evaluation for underlying causes, such as cystic fibrosis, immunoglobulin deficiencies, and mycobacterial disease, should be performed based on the clinical circumstances of the patient.

Bronchoscopy may be helpful for evaluating a mass or foreign body if identified on CT. However, bronchoscopy is less useful in evaluating bronchiectasis and would not be the next study of choice in this patient.

MRI of the chest has a limited role in evaluating bronchiectasis owing to multiple technical factors. It is an established diagnostic modality for evaluating pleural, hilar, and mediastinal abnormalities. However, it would not be an indicated study in this patient.

Although repeat chest imaging might be helpful to document resolution or progression of a pulmonary finding, delaying further evaluation in this patient with chronic symptoms would likely not be beneficial.