Filtering Pulmonary Function Tests Through Race/Ethnicity May Add To Biased Care

Walter Alexander

November 08, 2021

The use of race/ethnicity in medicine to explain and interpret pulmonary function test (PFT) differences between individuals may contribute to biased medical care and research. Furthermore, it may perpetuate health disparities and structural racism, according to a study published in CHEST.

Current practices of PFT measurement and interpretation are imperfect in their ability to accurately describe the relationship between function and health outcomes, according to Nirav R. Bhakta, MD, University of California, San Francisco, and colleagues.

The authors summarized arguments against using race-specific equations, while voicing genuine concerns about removing race from PFT interpretations, and described knowledge gaps and critical questions needing to be addressed for remediation of health disparities.

"Leaving out the perspectives of practicing pulmonologists and physiologists has global relevance for increasingly multicultural communities in which the range of values that represent normal lung function is uncertain," Bhakta said in an interview.

A Lesson in History

Tracing the history of spirometry, the authors stated that observations about vital lung capacity showing differences attributable to height, age, sex, and occupation (e.g., typesetter vs. firefighter) were then extended to include social classes and ultimately race. Whites showed greater average vital capacity for the same sex, height, and age than non-Whites.

While some investigators pointed to environmental sources (such as early life nutrition, respiratory illness, air pollution, exercise, and altitude), research into their mechanisms and magnitudes of effect was not pursued, but rather "a narrative of innate differences took hold," Bhakta and colleagues reported.

That sort of narrative risks comparison with those used to uphold slavery and structural racism in the past. More recently, such a narrative was used to deny disability claims of Welsh versus English White miners, and was expanded to interpret algorithms designed to predict expected lung function.

Use Of Standing Height Questioned

The current practice of using normalized standard height for lung function comparisons misses racial and ethnic differences in the proportion of sitting height to standing height shown in multiple studies, the authors stated. These comparisons may ignore effects on standing height of early-life nutrition, genetics, lung-specific factors such as respiratory infections and exposures to indoor and outdoor pollution, physical activity, and high altitude.

Using sitting height instead of standing height reduces lung volume differences up to 50% between White and Black populations, they noted, and socioeconomic variables, such as poverty and immigration status, accounted further for the differences seen. Population differences disappeared by as much as 90% when chest measurements used to estimate surface area or volume were more finely detailed.

The researchers warned, however, that, "because current clinical and policy algorithms rely so heavily on the comparison of an individual's observed lung function to that which is expected for similar people without typical respiratory disease, an abrupt change to not using race/ethnicity, if not paired with education and a reform of existing algorithms and policies, is also expected to have risks on average to groups of non-White individuals."

That could lead to potential challenges for some groups ranging from the ability to obtain employment in certain occupations, to being considered for potentially curative lung resections, or having access to home assisted ventilation and rehabilitation programs. "An abrupt change to not using race/ethnicity and taking a society's overall average as the reference range also has the potential to lead to delayed care, denial of disability benefits, and higher life insurance premiums to White individuals."

"Although evidence demonstrates differences in lung function between racial/ethnic groups, the premise that dividing lung function interpretation up by racial/ethnic background is helpful in the clinical setting is not a proven one." The authors cited some evidence that lung function interpretation without consideration of race/ethnicity has superior prognostic ability. In addition, research has shown only a weak relationship between lung function and work ability, according to the authors. More appropriate ways of assessing expected lung function for an individual in the absence of a diagnoses are under study.

Offering an Alternative

As an alternative to race, Bhakta and colleagues proposed using a range of values that include individuals across many global populations while still adjusting for sex, age, and height. The resultant value would represent a diverse population average and widen the limits of normal that can be expected in otherwise-healthy people.

The approach would include PFTs with other factors for clinical decision-making, but would allow clinicians and patients to appreciate the limitations of interpretation based on comparison to reference values. However, such an approach may miss pathophysiologically reduced lung function in some individuals, in which case lifesaving therapies, such as chemotherapy, lung cancer resection, and bone marrow transplantation could be withheld. In other instances the consequence would be overtesting and diagnosis, they acknowledged.

The authors further discussed general concerns about the use of race in interpretation of PFTs, addressing limits/considerations as well as knowledge and practice gaps.

For example, one particular concern involves the fact that race does not capture acculturation and mixed ancestry. The limit/consideration is the need to discover mechanisms for differences and to suggest societal interventions, and the knowledge gap pertains to ignorance regarding mechanisms leading to differences in lung function.

For the concern that race is not a proxy for an individual's genetics, the limit/consideration is that race captures only some genetics and the gap is the need for better genetic information. As an antidote to over reliance on lung function thresholds (without supporting data), they urged outcomes-based standards rather than comparisons with reference populations.

New Thinking Needed

Bhakta and colleagues pointed out that the forced expiratory volume in 1 second/forced vital capacity ratios important for diagnosis of obstructive lung disease are similar between racial/ethnic categories, underscoring the need for education about limitations of thresholds and reference values with regard to race, particularly as they are used to detect mild disease.

Ignoring race, on the other hand, can lead to unnecessary testing and treatment (with concomitant side effects), and anxiety.

"Reporting through race-based algorithms in the PFT laboratory risks portraying racial disparities as innate and immutable. By anchoring on the improved prediction of lung function from racial/ethnic-specific reference equations, we miss how the significant residual variation still leaves much uncertainty about the expected value for an individual," the authors concluded. "Given their origin and historical and current use in society, these racial/ethnic labels are better used to identify the effects of structural racism on respiratory health in research and ensure adequate representation in research, rather than in clinical algorithms."

One of the authors is a speaker for MGC Diagnostics. The others indicated that they had no relevant disclosures.

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