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To the Editor:
The American College of Occupational and Environmental Medicine (ACOEM) Guidance Statement,1 published in this issue, provides important updates to spirometry guidelines in the occupational setting. This ACOEM statement incorporates both the 2019 update of spirometry standards adopted by the American Thoracic Society (ATS) and European Respiratory Society (ERS)2 and the 2014 ATS Spirometry in the Occupational Setting Technical Standard.3 This editorial reviews how these three documents, which have overlapping audiences, work in harmony together and introduce changes to improve the overall quality of spirometry testing.
Surveillance of health indicators is a key feature of occupational health programs. In occupational environments that can potentially cause or exacerbate obstructive or restrictive lung diseases, spirometry is an important, and frequently mandated, tool to obtain an objective measure of this aspect of lung health. Spirometry is also a vital tool in clinical medicine and is required for diagnosing lung diseases such as chronic obstructive pulmonary disease and asthma, among other indications.2
There is a long history of workplace spirometry that has developed parallel to and often intertwined with, clinical spirometry testing. Standardization of spirometry in the United States was introduced in 1973 with proposed regulations for coal miners4. Then in 19785, the Occupational Safety and Health Administration (OSHA) promulgated the final Cotton Dust Standard containing requirements developed by the National Institute for Occupational Safety and Health (NIOSH) and the ATS—a collaboration between occupational health and clinical agencies. The elements of good testing mandated by this OSHA regulation served as the foundation for the subsequent 41 years of national and many international spirometry standards.
Workplace spirometry has unique aspects that do not impact clinical spirometry testing. Many workers have above average lung function and should be monitored over time as well as at each clinic visit. NIOSH-approved courses are mandated or recommended as training for technicians and the vast majority of technicians do not have respiratory backgrounds; regulations dictate the length of time for which medical records must be maintained, as well as what information can be provided to the employer; communication of results to the worker is specified in OSHA regulations; and compliance with applicable OSHA regulations is mandatory.
Since most occupational spirometry tests are periodic, consistency over time and within clinics of testing techniques, in particular, as well as reference values, is essential to permit accurate measurements of lung function to be assessed over working lifetimes. Without consistent testing techniques, a worker's measured values may be affected, which cannot be adjusted after the fact. Changes in testing technique or reference values may change the interpretation of results recorded by workers.
Qualified occupational health professionals need to be involved in the performance of tests as well in the interpretation of results, since a worker's lung function assessment can impact his/her job placement and/or ability to wear a mandated respirator. The impact of test results on a worker's livelihood, therefore, can be direct, and it differs from the impact on health and medical management that accompany clinical test results.
While many of the workers in occupational surveillance have normal lung function and no respiratory symptoms, patients performing spirometry in the clinical setting will likely have pulmonary disorders which may require special attention and consideration to help them achieve optimal results. Diagnoses of lung diseases, determination of treatment plans and monitoring the progression of disease, and the effectiveness of treatment rely on consistently good quality spirometry testing.
Reliable spirometry requires quality assurance of five main factors: (1) test procedure; (2) equipment; (3) technician performance; (4) subject/patient engagement and effort, and (5) interpreter expertise. National and international standards address these areas to ensure that the best possible spirometry result that can be achieved by the subject is recorded at the time of the test. Of all of these factors, the 2019 ATS/ERS changes that most affect occupational testing are procedural: (1) the determination of the revised end of the forced expiration, (2) confirmation that the expiration-only testing protocol, widely used in occupational testing, meets ATS/ERS recommendations when performed with maximal effort, and (3) use of sex assigned at birth as the designation of worker sex. All of these factors are included in the ACOEM Statement. These factors and other less substantial changes are discussed below.
The 2019 ATS/ERS standards accept a test procedure with an expiration-only protocol, which is more common in the occupational setting,6,7 or a procedure with an expiration–inspiration, which is more common in the clinical setting. Though the ATS/ERS update recommends a maximal inspiration following the forced expiration for flow-type spirometers, this final maximal inspiration is not required for a maneuver to be acceptable.
The biggest change in the procedure is the determination of the end of forced expiration. Minimum expiratory times have been eliminated and a maximum expiratory time of 15 seconds has been set. Spirometry systems are now required to provide audible alerts to technicians at end of expiration. Elimination of minimal expiratory times in the assessment of maneuver quality is especially useful in the occupational setting, where many young workers reach their forced vital capacity (FVC) plateaus very quickly. Though these tests were labeled as unacceptable in the past, they will now be acceptable. Going forward, users should ignore spirometer comments about inadequate length of exhalation (until the spirometer software is upgraded) and focus instead on curve shape.
ATS/ERS and ACOEM both recommend use of sex assigned at birth as the designation of worker sex, rather than reported adult sex identification. Such a designation will help the results of transgender workers to be more accurately evaluated.
The ACOEM Statement follows the requirement for increased accuracy in the ATS/ERS standards so that calibration verification using a 3 L calibration syringe has a maximum error tolerance of ±3%, down from the previous error tolerance of ±3.5%. While occupational standards and previous ATS/ERS standards8 focussed on volume based spirometers, they are far less common now, and the 2019 ATS/ERS update focusses more on flow-based spirometers, but continues to include volume-based devices.
Technician performance and accreditation of training programs have long been part of occupational spirometry testing, and were included in ACOEM statements and in the 2014 ATS Occupational Spirometry Statement. In the 2019 ATS/ERS Spirometry Update, requirements were also introduced to assess attainment and maintenance of technician competence in clinical spirometry facilities. The 2019 ATS/ERS standards have a greater emphasis on the technician's role in ensuring quality testing and have recommended system software changes to alert the technician to potential deficiencies in the performance of the test.
A survey of spirometry patients informed the revisions in the 2019 ATS/ERS update. It is anticipated that this information will also guide revision of technician training programs and increase the information regarding preparation for the test that will be circulated to subjects/patients prior to the spirometry test. For repeat maneuvers, it is important to check if the subject/patient is ready and how they feel about performing the next maneuver.
While the ACOEM guidelines deal extensively with spirometry interpretation, the 2019 ATS/ERS update is confined to technical standards. The 2005 ATS/ERS pulmonary function interpretation standards,9 on which the ACOEM guidelines and OSHA requirements are based,10 are currently under review. Nevertheless, though the 2019 ATS/ERS standards, with their international scope, recommend the use of the GLI (Global Lung Function Initiative) reference values11 as the default set, ACOEM sets national (USA) guidelines. As such, ACOEM prescribes use of the National Health and Nutrition Examination Survey, Round 3 (NHANES III) reference values12 which are drawn from a high quality study with a standardized testing protocol of a random sample of USA never smokers. Use of the NHANES III reference values for occupational testing in the US fully satisfies the 2019 ATS/ERS standards.
The 2014 ATS occupational spirometry recommendations that are most critical for occupational testing are: (1) scaling factor applied to Whites reference values to obtain more accurate reference values for Asian-American workers; (2) employ percent predicted method to evaluate change over time; and (3) recommendations for further evaluation of spirometric abnormalities in workers referred for follow-up. These factors are also discussed below.
- Since the NHANES III study12 developed reference values for Whites, African Americans, and Mexican Americans, but not Asian Americans, ATS recommends adjusting the Whites predicted and lower limit of normal values for FEV1 and FVC to obtain a more accurate reference value to evaluate Asian-American workers.3 The FEV1/FVC ratio is not adjusted.
- To evaluate potential excessive loss or variability of FEV1 over time, the ATS recommends the Percent Predicted Method as providing the most practical thresholds for clinicians to use in evaluating longitudinal FEV1 measurements.3 If FEV1% of predicted declines by 15% or more from the baseline test, it may indicate that the worker is experiencing excessive loss or measurement variability over time.
- Finally, the ATS made comprehensive recommendations for further evaluation of spirometric abnormalities in workers referred for follow-up.3
The 2020 ACOEM statement,1 and the 2019 ATS/ERS2 and 2014 ATS statements3 represent a continued tradition of working in harmony to develop spirometry standards that, while largely similar, recognize some important differences between occupational and clinical settings. All three of these documents seek to improve the outcomes for people requiring spirometry by ensuring that decisions regarding employment, diagnosis, and treatment are based on accurate measurements of lung function.
1. Townsend MC. “ACOEM Position Statement: Spirometry in Occupational Health - 2020.” J Occup Environ Med
2. Graham BL, Steenbruggen I, Miller MR, et al. Standardization of Spirometry – 2019 update: an Official American Thoracic Society and European Respiratory Society Technical Statement. Am Rev Resp Crit Care Med
3. Redlich CA, Tarlo SM, Hankinson JL, et al. Official American Thoracic Society Technical Standards: spirometry in the occupational setting. Am J Respir Crit Care Med
4. Department of Health, Education, Welfare. Second round of roentgenographic and medical examination in coal miners. Fed Regist
5. Occupational Safety, Health Administration. Part 1910-Occupational Safety and Health Standards - occupational exposure to cotton dust. Fed Regist
6. Townsend MC. The ATS/ERS 2019 Spirometry Statement and Occupational Spirometry Testing in the U.S (Letter to Editor). AJRCCM
7. Graham BL, Steenbruggen I. Reply to: The ATS/ERS 2019 Spirometry Statement and Occupational Spirometry Testing in the US. AJRCCM
8. Miller MR, Hankinson J, Brusasco V, et al. Standardisation of spirometry. Eur Respir J
9. Pellegrino R, Viegi G, Brusasco V, et al. Interpretative strategies for lung function tests. Eur Respir J
10. Occupational Safety and Health Administration (OSHA). Standards improvement project-phase IV. Fed Regist
11. Quanjer PH, Stanojevic S, Cole TJ, et al. Multi-ethnic reference values for spirometry for the 3-95 year age range: the global lung function initiative. Eur Respir J
12. Hankinson JL, Odencrantz JR, Fedan KB. Spirometric reference values from a sample of the general U.S. population. Am J Respir Crit Care Med