The guidelines established by the New York State Workers Compensation Board are formulated to aid healthcare professionals in conducting diagnostic testing for interstitial lung disease (ILD).
Tailored for medical practitioners, these Workers Compensation Board guidelines offer support in determining the appropriate diagnostic tests for individuals suspected of having ILD.
It’s crucial to note that these guidelines do not replace clinical judgment or professional experience. The decision on diagnostic testing for interstitial lung disease should be a collaborative one, involving the patient and their healthcare provider in consultation.
Spirometry
Spirometry serves as an initial and valuable test for assessing lung function. It offers physiological evidence for occupational interstitial lung disease (ILD) and helps distinguish between obstructive and restrictive lung patterns. Employing spirometry is a crucial step in both diagnosing and monitoring occupational ILD. It’s important to note that ILD diagnosis isn’t solely defined by spirometry results. When spirometry indicates abnormalities, further testing, including confirmation through lung volume testing as per ATS recommendations or referral to a specialist, is warranted.
For a comprehensive diagnostic approach to pulmonary occupational diseases, it is ideal to include measurements of lung volumes and diffusing capacity. Depending on clinical needs, additional analyses of gas exchange physiology, cardiopulmonary exercise testing, and/or a six-minute walk test can enhance the diagnostic and therapeutic evaluations of occupational lung diseases.
When conducting diagnostic spirometry testing:
– Use recommended equipment and procedures, administered by a properly trained technician.
– Adhere to the most recent recommendations or requirements of organizations like the American Thoracic Society, Occupational Safety and Health Administration (OSHA), NIOSH, and Mine Safety and Health Administration (MSHA).
– In cases of abnormal diagnostic spirometry, consider repeating the test on another occasion to ensure maximal inhalation, forceful exhalation, and complete exhalation by the individual.
– If results remain abnormal, assess short-term reversibility by repeating spirometry after the individual undergoes a standardized short-acting bronchodilator inhalation protocol.
– Once a satisfactory test is recorded, the diagnostic interpretation can compare the individual’s largest results with normal ranges derived from relevant, similar populations.
Analysis – The interpretation of spirometry testing for the assessment of workers vulnerable to occupational interstitial lung disease (ILD) involves multiple stages. Initially, the interpreter must scrutinize and provide feedback on the quality of the test, assessing whether acceptability criteria are satisfied. If the test is deemed suitable for interpretation, the next step involves adjusting for age, height, gender, and race/ethnicity using relevant reference tables for normal or predicted values. In cases where patients have undergone spirometry in the past, alterations in test results are examined over time.
Spirometry is recommended for both the diagnostic assessment and ongoing monitoring of individuals dealing with occupationally related interstitial lung diseases. Here are the specific indications:
For Diagnostic Purposes:
– Patients with a history and/or chest radiography consistent with ILD, coupled with workplace exposure aligning with plausible etiologies (e.g., workers expressing concerns about chronic or intermittent cough, shortness of breath, or diminished physical abilities).
– Spirometry is generally advised to be postponed if recent surgery, respiratory infections, or recent cardiac problems are present.
For Monitoring/Surveillance:
– Periodic spirometry, typically on a yearly basis, with a longitudinal assessment of pulmonary function loss is recommended for workers in occupations where exposures are known or suspected to be associated with the development of occupational lung disease.
– The longitudinal evaluation involves tracking the loss of Forced Expiratory Volume in one second (FEV1) over time, as FEV1 is the most consistently repeatable lung function parameter.
– This assessment should be performed when spirometry tests meet the required technical quality standards.
– Generally, a loss of FEV1 exceeding 50 ml/year is considered a pulmonary function loss surpassing the aging effect. Different methodologies proposed by organizations like the American College of Occupational Medicine (ACOEM), the American Thoracic Society (ATS), and the National Institute of Occupational Safety and Health (NIOSH) can be used to calculate and determine if the loss of pulmonary function exceeds the expected age-related decline. Specialized software, such as NIOSH’s Spirola, is available for calculating trends over time.
Static (Full) Lung Volumes
The measurement of static lung volumes, including Total Lung Capacity (TLC), Functional Residual Capacity (FRC), and Residual Volume (RV), is warranted to complement information obtained from a spirometry test when further clarification of diagnosis is needed. When a reduced Forced Vital Capacity (FVC) is observed in spirometry, it can be attributed to various disease processes. To conclusively determine the presence of a true restrictive disorder, where FVC is reduced below the lower limits of normal, the measurement of static lung volumes is essential for a comprehensive diagnosis.
Static lung volumes can also be utilized in obstructive diseases, such as emphysema or asthma, to assess the presence of air trapping. In these conditions, Total Lung Capacity (TLC) increases, along with an elevated RV/TLC ratio. The measurement of static lung volumes can be achieved through inert gas dilution or body plethysmography.
It is recommended to employ static lung volume measurements in the evaluation of Occupational Interstitial Lung Disease (ILD) to clarify a reduced FVC observed in spirometry, especially when the FEV1/FVC ratio appears normal. This is particularly crucial in instances where additional clarification of the diagnosis is needed.
Measurement of Oxygenation
Measuring oxygenation can be achieved through non-invasive oximetry or arterial blood gas sampling. Non-invasive oximetry assesses oxyhemoglobin or oxygen saturation of hemoglobin, offering a simple method commonly utilized in outpatient settings. On the other hand, arterial blood gas sampling is valuable for accurately measuring the partial pressure and saturation of oxygen, allowing the calculation of the alveolar-arterial oxygen gradient.
- It is recommended to use non-invasive oximetry measurements (pulse oximetry) to evaluate and manage Occupational Interstitial Lung Disease (ILD).
- Arterial blood gas measurements are recommended for select patients where precise measurement of the partial pressure and saturation of oxygen, as well as the calculation of the alveolar-arterial oxygen gradient, is necessary.
- Measurements of oxygenation are indicated in the assessment of Occupational ILD.
Chest Radiographs
The evaluation of pulmonary occupational disease should encompass imaging studies, with at least a PA and Lateral chest radiograph as part of the diagnostic work-up. Preferably, these radiographs should be interpreted following the International Labor Organization Classification for Pneumoconiosis.
Radiographs provide crucial structural and anatomical information about lung parenchyma and pleura, aiding in the differential diagnosis of occupational ILD. They also offer insights into the extent and progression of the disease. However, it’s important to note that while radiographs contribute to the diagnosis of occupational lung diseases, they are less sensitive and specific compared to CT/HRCT scans.
- Radiographs should be interpreted by a physician with the necessary training, experience, and skills in ILD and occupational lung disease diagnosis.
- To document patterns and severity of radiographic appearances of pneumoconiosis, it is preferable to interpret radiographs according to the International Labour Organization (ILO) classification, ideally by readers with “B” reader certification or individuals possessing appropriate training and skills. The recognition is given that certain standard-setting organizations require “B” reader qualifications in specific situations.
Posterior-Anterior (PA) and Lateral Chest Radiographs
For the diagnosis of occupational interstitial lung disease, it is recommended to perform Posterior-Anterior (PA) and Lateral Chest Radiographs. Physicians interpreting these radiographs for occupational lung disease diagnosis should possess appropriate training, experience, and skills. Ideally, they should have “B” reader certification for the International Labour Organization (ILO) classification system, or individuals with the suitable training and skills.
High Resolution Computed Tomography (HRCT) Scans /Computed Tomography (CT)
Consideration of HRCT/CT is advised in the evaluation of occupational ILD when additional diagnostics are required based on clinical findings, including spirometry and chest X-ray. Readers of HRCT/CT scans for occupational lung disease should have appropriate training and experience. It is recommended that a specialized thoracic radiologist reviews the chest CT scan.
- HRCT/CT is recommended in the evaluation of occupational ILD to confirm or exclude the diagnosis of ILD.
- HRCT/CT may be helpful in confirming or excluding a diagnosis of occupational ILD, and when indicated, it should cover lung, mediastinal, and high-resolution windows.
- The imaging is generally performed in the supine position, with prone imaging being useful in certain circumstances, such as confirming subtle peripheral and/or basilar findings representing interstitial abnormality.
- Inspiratory/expiratory imaging is particularly useful when considering air trapping associated with Hypersensitivity Pneumonitis (HP).
- HRCT/CT is recommended in the diagnostic workup of pneumoconiosis and other pulmonary occupational diseases, especially in lung diseases increasing the risk for lung cancer. This imaging study not only has diagnostic value but can also be used as a screening test for the early detection of lung cancer.
Magnetic Resonance Imaging (MRI) of the Chest
Using Magnetic Resonance Imaging (MRI) of the chest is not recommended as a primary diagnostic tool for occupational ILD.
PET/CT Scans of the Chest
In select cases, PET/CT scans of the chest are recommended in the evaluation of cancer associated with ILD, such as lung cancer and mesothelioma, and certain other comorbid condition
Carbon Monoxide Diffusing Capacity (DLco)
DLco, which stands for Diffusing Capacity of the Lungs, is a test designed to measure the transfer of gas from the lungs (alveoli/air spaces) to the blood circulating in the pulmonary capillaries. Typically, DLco refers to the single breath diffusing capacity test, where the patient inhales a known amount of CO, and the difference between the inhaled and exhaled CO is measured as the diffusing capacity of the lungs into the blood. This test indirectly evaluates the lungs’ ability to transfer oxygen to the blood using a calibrated test gas, CO. Proper methods and adjustments, as outlined in the ATS/ERS statement from 2017, should be followed to ensure a valid test.
- The DLco test is a valuable tool for assessing lung function and detecting various lung diseases, including ILD.
- The test should adhere to the ATS/ERS statement guidelines, ensuring at least two DLco tests are performed, with the results agreeing within 10%.
- Smoking status is crucial information to collect, as cigarette smoking can lead to measurable baseline levels of CO, causing increased backpressure and carboxyhemoglobin.
- It’s important to have the patient’s hemoglobin levels available, as anemia can lower the measured diffusion, and equations for correction of anemia are accessible.
Carbon Monoxide Diffusing Capacity (DLco) – Recommendations and Indications
The use of DLco is recommended for diagnosing occupational lung diseases. The test may assist in diagnosing gas exchange abnormalities in patients with lung disease. However, it’s essential to recognize that DLco may be influenced by different diseases and exposures, as outlined in . These factors must be considered when interpreting the test results.
Biological Sampling
Invasive Procedures
Invasive procedures, such as bronchoscopy, bronchoalveolar lavage analysis, and lung biopsy, are not routinely necessary for diagnosing occupational lung disease. However, they should be considered as part of the diagnostic toolkit when clinically indicated or essential to confirm or exclude a specific diagnosis. In certain conditions, specific CT findings are often deemed diagnostic, rendering invasive procedures less frequently required.
Sputum Samples and Bronchoalveolar Lavage (BAL)
When there is insufficient objective clinical evidence obtained from physical examination, chest radiographs, and spirometry, additional testing, including biological sampling, may be warranted to confirm the diagnosis of occupational ILD.
- Sputum Sample (both induced and spontaneous):
- Recommended in select patients as an aid for the diagnosis of occupational lung disease.
- If insufficient clinical objective evidence is obtained from physical examination, chest radiographs, and spirometry, additional testing, including sputum sampling, may be indicated to confirm the diagnosis of occupational ILD.
- Sputum sampling, although not mandatory due to the availability of modern testing like HRCT, can support the diagnosis of occupational lung disease. The sampling involves having the patient cough to produce sputum from deep within the lungs, with a recommended minimum sample volume of 15 mL to enhance sensitivity.
- Bronchoalveolar Lavage (BAL):
- Recommended in select patients as an aid for the diagnosis of occupational lung disease.
- To assist in the diagnosis of occupationally-related interstitial lung disease, BAL may be utilized, although it is not obligatory given the availability of modern testing like HRCT.
- BAL should be performed following the ATS guidelines on the performance of BAL for ILD.
Bronchoscopy and/or Lung Biopsy
Bronchoscopy and/or lung biopsy are recommended in very select patients to confirm or exclude a diagnosis in specific cases.
