When is a pulmonary function test recommended?

Indications for Pulmonary Function Testing (PFT)

Pulmonary function tests (PFTs) are recommended for patients with respiratory symptoms, known respiratory diseases, risk factors for pulmonary complications, or as part of surveillance protocols for specific conditions to detect early changes in lung function that may impact morbidity and mortality.

Primary Indications for PFT

Diagnosis and Evaluation of Respiratory Symptoms

• Persistent respiratory symptoms including:
  • Dyspnea (shortness of breath)
  • Chronic cough
  • Wheezing
  • Chest tightness
  • Exercise intolerance 1

Monitoring Known Respiratory Disease

• Follow-up of established respiratory conditions (accounts for approximately 53% of all PFT referrals) 2
• Assessment of disease progression or response to treatment 2
• Detection of early changes before clinical deterioration 3

Surveillance in High-Risk Populations

Neuromuscular Disease (NMD)

• Baseline and regular monitoring for patients with neuromuscular diseases:
  • Initial testing at age 7 years or when child can perform the test
  • Every 6 months minimum, adjusted based on disease progression
  • Tests should include: vital capacity (FVC or SVC), maximum inspiratory/expiratory pressures (MIP/MEP), sniff nasal inspiratory pressure (SNIP), and peak cough flow (PCF) 3

Post-Hematopoietic Stem Cell Transplantation (HSCT)

• Surveillance schedule for post-HSCT patients:
  • Every 3 months during first year post-HSCT
  • Every 3-6 months during second year
  • Every 6 months during third year
  • Annually after 3 years (up to 10 years post-HSCT)
  • More frequent testing for patients with chronic graft-versus-host disease (cGVHD) 3

Osteogenesis Imperfecta (OI)

• Baseline testing at age 7 years or when capable
• Follow-up testing based on severity:
  • Mild OI: Every 5 years if normal values and no symptoms
  • Severe OI: Annually 3

Preoperative Evaluation

• Preoperative risk assessment for:
  • Upper abdominal surgery
  • Cardiac surgery
  • Lung resection surgery 4
  • Tumor-infiltrating lymphocyte (TIL) cell therapy 3

Specific Risk Factors Requiring PFT

• Smoking history ≥20 pack-years
• Recent smoking cessation (within past 2 years) or current smoking
• History of pulmonary disease including pneumonitis, COPD, asthma
• Significant respiratory symptoms or abnormal chest X-ray
• History of pleural drainage within past 3 months 3
• Age >35 years with or without smoking history 1
• Family history of asthma in all age groups 1

Specific Parameters to Evaluate

Basic PFT Components

• Spirometry: FVC, FEV1, FEV1/FVC ratio (pre- and post-bronchodilator)
• Lung volumes: Total lung capacity (TLC), residual volume (RV), RV/TLC ratio
• Diffusing capacity (DLCO)
• Maximum respiratory pressures (MIP/MEP) for respiratory muscle strength
• Peak cough flow (PCF) - values <160 L/min indicate need for intervention 5

Additional Testing When Indicated

• 6-minute walk test: For patients unable to perform reliable spirometry 5
• Pulse oximetry: Values <90% require evaluation by a pulmonologist 5
• Arterial blood gases: To assess oxygenation and ventilation 5
• Cardiopulmonary exercise testing: To determine if exercise limitation is pulmonary, cardiac, or deconditioning 5

Special Considerations

Pulmonary Arterial Hypertension (PAH)

• PFTs with DLCO should be performed to evaluate for lung disease in patients with PAH
• Regular testing (every 6-12 months) for patients with systemic sclerosis to detect pulmonary vascular or interstitial disease 3

Tumor-Infiltrating Lymphocyte (TIL) Cell Therapy Candidates

• Spirometry and DLCO recommended for candidates with risk factors
• Postbronchodilator values: FEV1/FVC >70% or FEV1 >50% of predicted normal
• DLCO <50% may indicate patient is not a candidate for TIL cell therapy 3

Common Pitfalls to Avoid

• Misdiagnosis of restriction without TLC measurement (spirometry alone can be misleading)
• Overlooking cardiac causes of restrictive patterns
• Ignoring mild abnormalities that may indicate early disease
• Missing mixed patterns (both obstructive and restrictive components) 5

Key Thresholds for Referral to Specialist

• FVC <60% of predicted value
• FEV1/FVC <50% (absolute value)
• Pulse oximetry <90%
• DLCO <90% of predicted after volume adjustment
• History of >2 pneumonia episodes treated with antibiotics in last 5 years
• Any pneumonia episode requiring hospitalization in last 5 years 3, 5

PFTs are a valuable tool for early detection of respiratory abnormalities that can significantly impact morbidity and mortality. The frequency and specific components of testing should be tailored based on the underlying condition, risk factors, and clinical presentation.