Lung diseases

Tests

The goals with testing are to diagnose lung diseases, determine their causes where possible, and evaluate their severity. Many doctors will order blood gasses to evaluate oxygen and carbon dioxide levels, lung or pulmonary function tests (PFTs) to help diagnose and monitor lung function, and chest x-rays and or CT (computed tomography) scans to look at lung structure. Other testing is performed to help diagnose specific conditions.

Laboratory Tests

Blood gases – an arterial blood sample is collected to evaluate blood pH, oxygen and carbon dioxide
Full blood count (FBC) – to look for anaemia
Cystic fibrosis tests (CF gene mutation testing, sweat chloride, immunoreactive trypsin (IRT), stool trypsin) – to look for the genetic mutations causing cystic fibrosis and to diagnose the condition
Alpha-1 antitrypsin – to determine if patient has AAT deficiency
Sputum culture – to diagnose lung infections caused by bacteria
AFB smear and culture – to diagnose tuberculosis and nontuberculous mycobacteria (NTM)
Blood cultures – to diagnose bacteria and sometimes yeast infections that have spread into the blood
Influenza tests – to diagnose influenza
Lung biopsy – to evaluate lung tissue for damage and for cancer
Sputum cytology – to evaluate lung cells for abnormal changes and for cancer
Fetal lung maturity (FLM) tests - used to evaluate the lung maturity of a fetus and may include tests for lecithin/sphingomyelin (L/S) ratio, phosphatidylglycerol (PG), foam stability index (FSI), or lamellar body counts (LBC). May be used to determine age of gestation before caesarean delivery or when a pregnant woman is having symptoms of premature labour.
Drug sceen - to detect drugs in overdoses that lead to decreased respiration or acute respiratory distress

Lung function tests (pulmonary function tests, PFT)
A few of the more common tests are listed below. For more complete information visit the website for Johns Hopkins Medicine: Pulmonary Function Laboratory.

Spirometry – measures the amount and rate of air exhalation as a patient blows out through a tube. It is performed to evaluate narrowed or obstructed airways.
Air flow with a peak flow meter – measures the rate of exhalation. It can be used at home by patients with asthma to help monitor their condition.
Lung volume – the quantity of air a person takes into their lungs and how much is left in the lungs after exhalation. Helps evaluate the elasticity of the lungs, the movement of the rib cage, and the strength of the muscles associated with respiration.
Diffusing capacity measurement – assesses the transfer of oxygen from the lung air sacs to the bloodstream by evaluating how much carbon monoxide is absorbed when a small quantity is inhaled (not enough to harm).

Imaging studies

Chest x-ray – to look at lung structure and chest cavity
CT (computed tomography) scan – a more detailed evaluation of lung structure
MRI (magnetic resonance imaging) – detailed pictures of organs and vessels in the chest
Ultrasound – used to detect fluid between the pleural membranes
Nuclear lung scanning – used to help detect pulmonary embolism and rarely, to evaluate the effectiveness of lung cancer treatment
Positron emission tomography (PET) scans – used to help diagnose lung cancer

Other tests

Electrocardiogram (ECG) – to look at heart rhythm, to determine if heart disease may be affecting breathing
Sleep studies – usually performed at special sleep centers to help determine whether a person is breathing normally during sleep.