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 gases 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

Some tests that may be performed to help determine a person's health status and how well the lungs are working include:

• Blood Gases – an arterial blood sample is collected to evaluate blood pH, oxygen and carbon dioxide
• Complete Blood Count (CBC) – to evaluate blood cells and check for anemia
• Comprehensive Metabolic Panel (CMP) – to evaluate organ function and chemical and electrolyte balances

Additional tests may be performed to help diagnose certain lung conditions:

• Cystic Fibrosis tests 
  • CF Gene Mutation Testing – to look for the genetic mutations that cause cystic fibrosis
  • Sweat chloride
  • Immunoreactive trypsin (IRT) 
  • Stool trypsin
• Alpha-1 antitrypsin – to determine if a person has AAT deficiency
• Pleural fluid analysis – to investigate the cause of fluid accumulation between the chest wall and the outside of each lung; it may be due to, for example, cancer or infections.
• Allergy tests – may be ordered to determine asthma triggers
• Tests for specific infections:
  • Sputum culture – to diagnose lung infections caused by bacteria or fungi
  • 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
  • Respiratory syncytial virus (RSV)
  • Pertussis – to diagnose whooping cough
  • Fungal tests
• Tests for autoantibodies may help determine if an autoimmune disorder is affecting the lungs:
  • Anti-nuclear antibody (ANA)
  • Extractable nuclear antigen (ENA) panel
  • Anti-ds DNA
• Lung biopsy – to evaluate lung tissue for damage and for cancer
• Sputum cytology – to evaluate lung cells for abnormal changes and for cancer
• Soluble mesothelin-related peptides (SMRP) – to monitor mesothelioma, a specific type of lung cancer
• Drug screen – to detect drugs in overdoses that can lead to decreased respiration or acute respiratory distress
• 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 cesarean delivery or when a preganant woman is having symptoms of premature labor.

Lung Function Tests (Pulmonary Function Tests, PFT)
A few of the more common tests are listed below. For more complete information, visit the web site for John Hopkins Medicine: Pulmonary Function Laboratory.

• Spirometry – measures the amount and rate of air exhalation as a person 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 people 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

For more on these, see the RadiologyInfo.org web site.

Other Tests

• Electrocardiogram (EKG, 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