PFT with diffusion is a breathing test combination: standard pulmonary function testing (spirometry and lung volumes) plus measurement of diffusion capacity (DLCO). It evaluates airflow, lung volumes and how effectively gas (using a small carbon monoxide tracer) transfers from alveoli into blood. It helps diagnose emphysema, interstitial lung disease and pulmonary vascular disease. Avoid smoking or some inhalers before testing.

A diffusion test (disc diffusion) evaluates how susceptible bacteria are to antibiotics. A bacterial lawn is spread on agar, antibiotic-impregnated discs are placed on the surface, and after incubation the clear zones (zones of inhibition) around discs are measured. Zone sizes indicate susceptible, intermediate, or resistant. Results—produced under standardized conditions—help clinicians select effective antibiotics.

Pulmonary function test costs vary by country and facility. In the US private clinics typically charge about $50–$500 depending on whether it’s simple spirometry or full PFTs (diffusion, plethysmography). In the UK it’s usually free on the NHS or about £60–£250 privately. In India expect roughly ₹300–2,500. Insurance or public healthcare often covers medically necessary tests.

Pulmonary function tests (PFTs) detect functional lung damage by measuring airflow, lung volumes and gas exchange (including DLCO). They identify obstructive or restrictive patterns, quantify severity, and monitor progression or treatment response. However, PFTs show functional impairment rather than exact structural changes—localized scarring, early emphysema, or bronchiectasis often require chest imaging (X‑ray or CT) for definitive diagnosis.

A pulmonary function test (PFT) is noninvasive and generally not painful. You breathe through a mouthpiece and perform normal and forced breaths; this can cause temporary discomfort such as coughing, shortness of breath, lightheadedness, chest tightness or fatigue. Bronchial challenge tests may provoke wheeze. Serious complications are rare; tell staff about recent heart problems, bleeding or severe symptoms before testing.

Diffusion capacity (DLCO) measures gas transfer from alveoli to blood. A good DLCO is within the predicted reference range—generally ≥80% of predicted for age, sex, height and hemoglobin (often ~20–30 mL/min/mmHg). Values 60–79% indicate mild reduction, 40–59% moderate, and <40% severe impairment. Results should be interpreted with clinical context and hemoglobin correction.