Bronchiectasis is diagnosed primarily through a high-resolution CT scan (HRCT) of the chest, which can show the widened, damaged airways that define the condition. But the diagnostic process typically starts well before that scan, beginning with a pattern of symptoms that prompts your doctor to look deeper, and continuing afterward with tests to figure out what caused the damage in the first place.
Symptoms That Raise Suspicion
The hallmark symptom is a chronic cough that produces mucus, present in up to 98% of people with bronchiectasis. More than 70% of patients produce sputum daily, and it’s typically mucoid and relatively odorless (though it can become discolored or foul-smelling during flare-ups). A persistent wet cough that doesn’t clear up after a standard course of antibiotics is a strong signal. One study of children with chronic wet cough found that those whose cough persisted after four weeks of oral antibiotics were 20 times more likely to have bronchiectasis than those who improved.
Other common symptoms include recurring chest infections, shortness of breath, and occasionally coughing up blood. If you’ve had repeated lung infections over months or years, especially with daily mucus production, that pattern is what typically leads a doctor to order imaging.
The CT Scan: How the Diagnosis Is Confirmed
A high-resolution CT scan is the definitive test. Standard chest X-rays can miss bronchiectasis entirely or show only vague abnormalities, so HRCT is needed for a reliable diagnosis. The scan produces detailed cross-sectional images of the lungs that reveal the size and shape of your airways.
Radiologists look for airways that are wider than the blood vessel running alongside them. In healthy lungs, a bronchial tube and its neighboring artery are roughly the same diameter. In bronchiectasis, the airway balloons to two, three, or even four times the width of the adjacent artery. This creates what’s sometimes called the “signet ring sign” on the scan, where the enlarged airway and smaller artery together resemble a ring with a stone.
The scan also reveals the shape of the damage. Cylindrical bronchiectasis shows uniformly widened tubes. Varicose bronchiectasis has an irregular, beaded appearance. Cystic (or saccular) bronchiectasis, the most severe form, shows balloon-like clusters at the ends of the airways. Thickened bronchial walls are another common finding, though radiologists don’t always agree on how to grade the severity of wall thickening. Studies show poor consistency between readers when scoring this feature, with interobserver agreement as low as 0.21 on the standard agreement scale.
Breathing Tests
Spirometry, a simple breathing test where you blow into a tube as hard and fast as you can, helps measure how much your lung function has been affected. It doesn’t diagnose bronchiectasis on its own, but it establishes a baseline and helps guide treatment.
The most common pattern is airflow obstruction, meaning air has trouble getting out of your lungs. About 60 to 73% of bronchiectasis patients show this obstructive pattern on spirometry. Roughly 20 to 24% have a mixed pattern combining obstruction and restriction (where the lungs also can’t fully expand). Pure restriction is less common, seen in about 3 to 10% of patients. A small percentage, around 6%, have completely normal spirometry despite having visible damage on their CT scan.
These numbers matter because the degree of obstruction feeds into severity scoring systems used to track the disease over time.
Finding the Underlying Cause
Once the CT confirms bronchiectasis, the next step is figuring out why it developed. This matters because treating the underlying cause, when one can be found, may slow further damage. However, in 30 to 50% of cases, no clear cause is ever identified.
The standard workup includes several targeted tests:
- Immunoglobulin levels check whether your immune system produces enough antibodies. Low levels (immunodeficiency) leave you vulnerable to repeated infections that can progressively damage the airways.
- Cystic fibrosis screening involves a sweat test, which measures the salt concentration in your sweat. Genetic testing may follow if results are borderline or if you have other features suggestive of cystic fibrosis.
- Allergic bronchopulmonary aspergillosis (ABPA) is a fungal allergy that causes airway inflammation and characteristic central bronchiectasis on CT. Diagnosing it requires a combination of blood tests: total IgE levels (values above 1,000 IU/mL are the hallmark), specific IgE antibodies to the Aspergillus fungus, IgG antibodies to Aspergillus, and an eosinophil count. No single test confirms ABPA on its own.
- Alpha-1 antitrypsin levels screen for a genetic condition where the body doesn’t produce enough of a protein that protects the lungs.
- Autoimmune screening looks for conditions like rheumatoid arthritis or inflammatory bowel disease, both of which can contribute to bronchiectasis.
Your doctor may also test for primary ciliary dyskinesia, a rare inherited condition where the tiny hair-like structures lining the airways don’t work properly, leaving mucus to pool and breed infection. This is more commonly investigated in younger patients or when bronchiectasis appears alongside chronic sinus problems and, in some cases, organs positioned on the opposite side of the body from normal.
Sputum Cultures
A sputum sample, collected when you cough up mucus, is sent to a lab to identify which bacteria are colonizing your airways. This doesn’t diagnose bronchiectasis itself, but it shapes how flare-ups are treated and helps assess severity.
A systematic review of sputum cultures found the two most common bacteria are Haemophilus influenzae (isolated in about 29% of patients) and Pseudomonas aeruginosa (about 28%). Other common organisms include Staphylococcus aureus (12%), Streptococcus pneumoniae (11%), and Moraxella catarrhalis (8%). Pseudomonas colonization in particular is associated with worse outcomes and more frequent exacerbations, which is why identifying it early matters for long-term management.
Distinguishing Bronchiectasis From Similar Conditions
Bronchiectasis shares symptoms with COPD and asthma, particularly the chronic cough, mucus production, and shortness of breath. All three can coexist, which complicates the picture. The CT scan is the clearest differentiator, since neither COPD nor asthma alone produces the permanent airway widening seen in bronchiectasis.
Bronchiectasis and COPD both tend to involve neutrophilic (infection-driven) inflammation and chronic bacterial colonization of the airways. Asthma, by contrast, more often involves eosinophilic (allergy-driven) inflammation, though overlap exists. Experts recommend that patients with severe COPD who have frequent infections undergo a CT scan specifically to check for coexisting bronchiectasis, since the combination is linked to a worse prognosis.
When bronchiectasis appears in just one area of the lung rather than spread across both sides, doctors may recommend bronchoscopy, a procedure where a thin camera is passed through the nose or mouth into the airways. This is done to rule out a blockage such as a tumor, an inhaled foreign body, or structural narrowing that could be causing localized damage.
Severity Scoring After Diagnosis
After diagnosis, two validated scoring systems help predict how the disease will behave over time. The Bronchiectasis Severity Index (BSI) incorporates nine factors: age, body mass index, lung function, prior hospitalizations, exacerbation frequency, breathlessness score, whether Pseudomonas is present, colonization with other organisms, and how widespread the damage looks on the CT. Scores range from 0 to 26, with 0 to 4 classified as mild, 5 to 8 as moderate, and 9 or above as severe.
The FACED score is simpler, using just five variables: lung function, age, Pseudomonas colonization, radiological extent, and breathlessness. It scores from 0 to 7, with 0 to 2 being mild, 3 to 4 moderate, and 5 or higher severe. Both tools help your care team decide how aggressively to manage the condition and how closely to monitor you going forward.