SERIES “ATS/ERS TASK FORCE: STANDARDISATION OF LUNG FUNCTION TESTING” 

Edited by V. Brusasco, R. Crapo and G. Viegi 

Number 5 in this Series 







This section is written to provide guidance in interpreting pulmonary function tests (PFTs) to medical directors of hospital-based laboratories that perform PFTs, and physicians who are responsible for interpreting the results of PFTs most commonly ordered for clinical purposes. Specifically, this section addresses the interpretation of spirometry, bronchodilator response, carbon monoxide diffusing capacity ( D L,CO) and lung volumes.

The sources of variation in lung function testing and technical aspects of spirometry, lung volume measurements and D L,CO measurement have been considered in other documents published in this series of Task Force reports 1–4 and in the American Thoracic Society (ATS) interpretative strategies document 5.

An interpretation begins with a review and comment on test quality. Tests that are less than optimal may still contain useful information, but interpreters should identify the problems and the direction and magnitude of the potential errors. Omitting the quality review and relying only on numerical results for clinical decision making is a common mistake, which is more easily made by those who are dependent upon computer interpretations.

Once quality has been assured, the next steps involve a series of comparisons 6 that include comparisons of test results with reference values based on healthy subjects 5, comparisons with known disease or abnormal physiological patterns ( i.e. obstruction and restriction), and comparisons with self, a rather formal term for evaluating change in an individual patient. A final step in the lung function report is to answer the clinical question that prompted the test.

Poor choices made during these preparatory steps increase the risk of misclassification, i.e. a falsely negative or falsely positive interpretation for a lung function abnormality or a change …

https://erj.ersjournals.com/content/erj/26/5/948.full.pdf

Interpretative strategies for lung function tests

https://ebmt.co.uk/wp-content/uploads/2013/08/GVHD1.pdf

National Institutes of Health Consensus Development Project on Criteria for Clinical Trials in Chronic Graft-versus-Host Disease: I. Diagnosis and Staging Working Group Report

The aim of the Task Force was to derive continuous prediction equations and their lower limits of normal for spirometric indices, which are applicable globally. Over 160,000 data points from 72 centres in 33 countries were shared with the European Respiratory Society Global Lung Function Initiative. Eliminating data that could not be used (mostly missing ethnic group, some outliers) left 97,759 records of healthy nonsmokers (55.3% females) aged 2.5-95 yrs. Lung function data were collated and prediction equations derived using the LMS method, which allows simultaneous modelling of the mean (mu), the coefficient of variation (sigma) and skewness (lambda) of a distribution family. After discarding 23,572 records, mostly because they could not be combined with other ethnic or geographic groups, reference equations were derived for healthy individuals aged 3-95 yrs for Caucasians (n=57,395), African-Americans (n=3,545), and North (n=4,992) and South East Asians (n=8,255). Forced expiratory value in 1 s (FEV(1)) and forced vital capacity (FVC) between ethnic groups differed proportionally from that in Caucasians, such that FEV(1)/FVC remained virtually independent of ethnic group. For individuals not represented by these four groups, or of mixed ethnic origins, a composite equation taken as the average of the above equations is provided to facilitate interpretation until a more appropriate solution is developed. Spirometric prediction equations for the 3-95-age range are now available that include appropriate age-dependent lower limits of normal. They can be applied globally to different ethnic groups. Additional data from the Indian subcontinent and Arabic, Polynesian and Latin American countries, as well as Africa will further improve these equations in the future.

https://erj.ersjournals.com/content/erj/40/6/1324.full.pdf

Multi-ethnic reference values for spirometry for the 3–95-yr age range: the global lung function 2012 equations

https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(07)61377-4.pdf

International variation in the prevalence of COPD (The BOLD Study): a population-based prevalence study

Background: Measurement of fractional nitric oxide (NO) concentration in exhaled breath (FeNO) is a quantitative, noninvasive, simple, and safe method of measuring airway inflammation that provides a complementary tool to other ways of assessing airways disease, including asthma. While FeNO measurement has been standardized, there is currently no reference guideline for practicing health care providers to guide them in the appropriate use and interpretation of FeNO in clinical practice.Purpose: To develop evidence-based guidelines for the interpretation of FeNO measurements that incorporate evidence that has accumulated over the past decade.Methods: We created a multidisciplinary committee with expertise in the clinical care, clinical science, or basic science of airway disease and/or NO. The committee identified important clinical questions, synthesized the evidence, and formulated recommendations. Recommendations were developed using pragmatic systematic reviews of the literature and the GRADE approach....

/pdf/an-official-ats-clinical-practice-guideline-interpretation-1iahut6ven.pdf

An official ATS clinical practice guideline: interpretation of exhaled nitric oxide levels (FENO) for clinical applications.

Spirometric reference values for Caucasians, African-Americans, and Mexican-Americans 8 to 80 yr of age were developed from 7,429 asymptomatic, lifelong nonsmoking participants in the third National Health and Nutrition Examination Survey (NHANES III). Spirometry examinations followed the 1987 American Thoracic Society recommendations, and the quality of the data was continuously monitored and maintained. Caucasian subjects had higher mean FVC and FEV 1 values than did Mexican-American and African-American subjects across the entire age range. However, Caucasian and Mexican-American subjects had similar FVC and FEV 1 values with respect to height, and AfricanAmerican subjects had lower values. These differences may be partially due to differences in body build: observed Mexican-Americans were shorter than Caucasian subjects of the same age, and African-Americans on average have a smaller trunk:leg ratio than do Caucasians. Reference values and lower limits of normal were derived using a piecewise polynomial model with age and height as predictors. These reference values encompass a wide age range for three race/ethnic groups and should prove useful for diagnostic and research purposes. Hankinson JL, Odencrantz JR, Fedan KB. Spirometric reference values from a sample of the general U.S. population. AM J RESPIR CRIT CARE MED 1999;159:179‐187.

https://www.atsjournals.org/doi/pdf/10.1164/ajrccm.159.1.9712108

Spirometric Reference Values from a Sample of the General U.S. Population

Early in the COVID-19 pandemic, demand for N95 respirators far exceeded the supply, leading to widespread shortages. Initially, the US Centers for Disease Control and Prevention did not recommend N95 respirators in nonhealthcare settings, in order to reserve them for healthcare workers. As N95s became more available, the recommendations were updated in May 2021 to include N95 respirators for nonhealthcare settings. In this study, we estimated the numbers of N95s needed for nonhealthcare essential workers in the United States. This information is valuable for crisis preparedness and planning for future large-scale communicable respiratory infectious disease epidemics or pandemics. We adapted a spreadsheet-based tool originally built to estimate the potential demand for N95 respirators during an influenza pandemic. We defined nonhealthcare essential occupations according to the 2020 US Department of Homeland Security guidance and used US Bureau of Labor Statistics employment numbers and Occupational Information Network data as model parameters. We modeled minimum, intermediate, and maximum N95 provision scenarios (as 1, 2, and 5 N95 respirators, respectively) per week per worker, for pandemic durations of 15 and 40 weeks. For 85.15 million nonhealthcare essential workers during a 15-week pandemic, an estimated 1.3 billion N95 respirators would be needed under minimum provision scenarios, 2.6 billion for intermediate provision, and 6.4 billion for maximum provision. During a 40-week pandemic, these estimates increased to 3.4 billion, 6.8 billion, and 17 billion. Public health authorities and policymakers can use these estimates when considering workplace respirator-wearing practices, including prioritization of allocation, for nonhealthcare essential workers. Our novel spreadsheet-based tool can also be used to quickly generate estimates of other preparedness and response equipment.

Kathleen B. Fedan

Papers

Spirometric Reference Values from a Sample of the General U.S. Population

Estimated N95 Respirator Needs for Nonhealthcare Essential Workers in the United States During Communicable Respiratory Infectious Disease Pandemics.