Pulmonary Function Testing Guidelines

Introduction to PFT and Spirometry

Spirometry is a component test within the broader category of pulmonary function testing (PFT), which encompasses multiple distinct measurements of lung function, as stated by the European Respiratory Society 1

Spirometry specifically measures Forced vital capacity (FVC), the total volume exhaled during a forceful breath, Forced expiratory volume in 1 second (FEV1), the volume exhaled in the first second, and FEV1/FVC ratio, used to identify airflow obstruction, according to the European Respiratory Society 2
Spirometry also includes flow-volume curves, a graphical representation of expiratory airflow, as described by the American Thoracic Society 3

A complete pulmonary function test battery includes spirometry plus additional measurements, such as lung volume measurements, including Total lung capacity (TLC), Residual volume (RV), and Functional residual capacity (FRC), as recommended by the European Respiratory Society 1
Comprehensive PFT also includes Diffusing capacity (DLCO), which measures gas exchange across the alveolar-capillary membrane, assessing parenchymal lung disease, as stated by the European Respiratory Society and the American Thoracic Society 1, 3

Spirometry alone cannot diagnose restrictive lung disease and has limitations, including inability to distinguish between true restriction and pseudorestriction, quantify hyperinflation or air trapping, assess gas exchange abnormalities, or measure static lung volumes, as noted by the European Respiratory Society and the American Thoracic Society 1, 3

The American Thoracic Society recommends that interpretation of any pulmonary function testing should include quality assessment, comparison to reference values, identification of ventilatory defect patterns, and correlation with clinical context, whether performing spirometry alone or comprehensive PFT, as stated by the American Thoracic Society and the European Respiratory Society 1, 4
For initial screening and monitoring of obstructive diseases, spirometry provides essential measurements, but comprehensive PFT is necessary for accurate diagnosis when clinical suspicion exists for interstitial lung disease, neuromuscular weakness, chest wall disorders, or unexplained dyspnea with normal spirometry, as recommended by the American Thoracic Society and the European Respiratory Society 2, 3

The American Thoracic Society recommends that only Forced Vital Capacity (FVC), Forced Expiratory Volume in 1 second (FEV1), and FEV1/FVC need to be routinely reported for spirometry, as most other calculated parameters do not add clinical utility 5, 6

The American Thoracic Society notes that comprehensive pulmonary function testing, including spirometry and static lung volumes and Diffusing Capacity (DLCO), is necessary for accurate diagnosis when clinical suspicion exists for certain conditions, and recommends using "spirometry and, where feasible, static lung volumes and DLCO" in post-hematopoietic stem cell transplantation surveillance 7, 8, 9

The American College of Rheumatology recommends complete PFTs for suspected interstitial lung disease, as they reveal restrictive physiology and impaired gas exchange 10
The European League Against Rheumatism suggests baseline and serial monitoring with PFTs every 3-6 months initially, then 6-12 months once stable, for connective tissue disease screening 10, 11
The European Respiratory Society recommends objective measures, such as PFTs, to confirm asthma diagnosis and prevent overdiagnosis that occurs in 33% of patients diagnosed without PFTs 12

The American Thoracic Society states that oscillometry may be useful for detecting small airway dysfunction, and is more sensitive than spirometry for peripheral airways disease, but requires further validation before routine clinical use 10, 13
The American Academy of Pediatrics suggests that oscillometry can be used in young children (preschool age) who cannot complete forced expiratory maneuvers 13

The American College of Rheumatology recommends monitoring established disease requiring monitoring with standard PFTs every 6-12 months for stable disease, and more frequently (every 3 months) if progressive or symptomatic 10, 11