Elizabeth Flagg

To continue our recent discussions on disease testing, today we’re talking about swabbing and swabs.

Perhaps you’ve been lucky enough to experience a swab test firsthand. As testing becomes more widespread, we are all likely to have a nasopharyngeal swab taken for a COVID-19 test. When I was a child, maybe around seven, I remember going to the doctor’s office to be tested for influenza, another virus that replicates in the nasopharynx. When the nurse first pulled the slim, wire swab out of the packaging, I thought no way. No way that daunting, 5-cm long wire will fit up my nose. Sadly, I was mistaken. I won’t lie – it wasn’t the most pleasant experience. The tickling sensation lingered in my throat long after the swab had been removed. I still felt it even after my results had come back – negative, luckily for me. Just a common cold!

This kind of swab is referred to as a nasopharyngeal swab, which I learned many years later. Nasopharyngeal swabs are used to collect samples from the back wall of the nasopharynx (hence the name), which is where the nasal passages meet the throat. Other common swab tests include nasal swabs and oropharyngeal (throat) swabs.

Nasal swabbing vs. nasopharyngeal swabbing from link.

Swabs are made out of a number of different materials. Since the nasopharynx is much farther back in the nasal passage, the swab needed to get there must be longer and somewhat bendable. The swabs used for sampling the nostrils and throat are generally stiffer and shaped like long Q-tips. The materials that comprise the tips of these swabs are different, too. If you are trying to get material out of the oral or nasal cavities for testing, you need a surface at the tip that is good at grabbing that material. It is also important to be able to wash the material off and into the testing solution when needed. Thus, regular cotton is often not suitable.

In terms of COVID-19 testing, the swabs you’re most likely to encounter are nasopharyngeal and nasal swabs. Nasal swabs are less invasive. The swab only needs to be inserted 1 cm into the nostril and rubbed along the septum for a few seconds. Nasopharyngeal swabs, on the other hand, require a longer swab, which is inserted about 4-6 cm back into the nostrils (about half-way between the entrance to the nares and the base of the ear). The swab is then rotated inside the nasal passages and left in place for a few seconds to absorb the sample.

Check out Dr. Klapperich demonstrating anterior nares swabbing (AN) here and here on TikTok!

More fun with nostril swabbing! pic.twitter.com/3TyKUbqogu
— Cathie Klapperich (@DrKlapperich) July 25, 2020

Swabs made to sample the nasopharynx usually have a tip made of plastic foam, or another material with lots of surface area. These are called “flocked” swabs. Only a few factories in the world make these swabs, which is why you regularly hear about swab shortages for testing. Sadly, using a version of a regular Q-tip would not be a suitable replacement. There are a number of innovative groups around the world looking for ways around this shortage. Some of them include 3D printing swabs made from medical grade plastics. All swabs that are used to apply topical medications or collect fluid samples are considered Class I medical devices by the FDA.

In studies comparing the sensitivity of nasal vs nasopharyngeal swabs for influenza, nasopharyngeal swabs were found to be slightly more sensitive (94% vs. 89% sensitivity). This means that for the flu, a nasal swab sample will lead to a false-negative test result more often than a nasopharyngeal swab. But despite their inferior sensitivity, nasal swabs are simpler and useful for “self-swabbing”- taking your own sample to send or have delivered to a testing facility. According to the most recent update to the CDC’s COVID-19 specimen collection guidelines, nasal swabs taken by a healthcare worker or via self-swabbing are acceptable if taking a nasopharyngeal swab is not possible. But these guidelines are sure to change as more information comes out about how swab type affects false-negative rates for COVID-19. Early indications are that nostril swabs are not as good as nasopharyngeal swabs for this new virus.

A spirometer is a medical device often used to assess respiratory function and diagnose respiratory diseases, including asthma, chronic obstructive pulmonary disease, and asbestosis.¹ To use the device, you inhale and exhale as deeply as possible into a breathing tube attached to the spirometer itself, which measures your forced vital capacity (the maximum amount of air you can breathe in) and forced expiratory volume (how much you can breathe out in 1 second).¹

Figure 1: This shows the basic set-up of a modern spirometer test. The patient wears a nose clip and breathes into a mouthpiece, and a monitor displays a graph of their inhaled and exhaled volume. (Source Wikipedia)

For each patient who is tested using a spirometer, the operator must enter information about the patient, including their age, sex, height, and race.² Unbeknownst to many operators, selecting a patient’s race enables a “race correction” setting programmed directly into the spirometer software – typically a 10-15% lower baseline lung capacity for patients identified as Black, and 4-6% lower for patients identified as Asian.³ Despite conflicting studies contesting the validity of using racial correction factors,⁴ it continues to be taught in modern science. This idea that non-whites have intrinsically lower lung capacity began as a justification for slavery, and the ramifications of this notion have continued to manifest in modern-day medical devices.

In Thomas Jefferson’s “Notes on the State of Virginia,” the former president and slaveholder described deficiencies in “the pulmonary apparatus” of Black slaves.⁵ Plantation physician Samuel Cartwright further elaborated on Jefferson’s sentiments with his own spirometer studies, reporting a 20% “deficiency in the negro” in regards to lung capacity.⁶ Cartwright promoted slavery on the grounds that forced labor was necessary for Black people’s health due to their innately lower lung capacity. He stated that “it is the red vital blood sent to the brain that liberates their mind when under the white man’s control.” ⁶

After the Civil War, Benjamin Apthorp Gould further expanded on Cartwright’s work by comparing the lung capacity of Black and White soldiers. Although Gould did not account for height, age, or the living conditions of recently emancipated slaves, Gould’s conclusions mirrored those who came before him: “full blacks” had lower lung capacity than “whites.” ^2,5,7 Gould’s study is still cited in scientific articles today.²

Over the course of the 20th century, researchers continued to fuel the idea of innate racial differences in lung function, repeatedly failing to account for the influence of socioeconomic conditions. In a review of articles published between 1922-2008 comparing lung function between races, 94% of articles did not examine race in the context of socioeconomic status.⁸ Although it is often ignored in research articles, lower lung capacity has been associated with poverty in past studies, as well as other social determinants including environmental toxin exposure and healthcare inaccessibility.^2,5

In 1984, J.E. Myers published an article that questioned the body of data supporting innate racial differences in lung function. Myers conducted his own spirometer studies of Black workers in South Africa, and his calculations showed that the published South African standards considerably underestimated the lung volume of Black people.⁴ Myers also challenged the assumptions made in previous studies, pointing out that they neglected to account for socioeconomic factors including environmental pollutants, housing quality and nutrition quality.⁴

Several years after Myers’ article, in 1999, asbestos manufacturer Owens Corning used the argument that Black people have an intrinsically lower lung capacity to evade lawsuits from Black workers with lung damage. The company tried to argue that Black workers should be held to a different standard when assessing asbestos-induced lung damage because Black people consistently score lower on pulmonary function tests.⁹ The motion was overruled, but the case highlighted how historic assumptions on race have infiltrated modern lung research. As in the case of Owens Corning, modified lung function standards based on race have the potential to reduce diagnosis rates for respiratory illnesses and lung damage.

Current spirometers implement “race correction” automatically, defining race as a purely genetic difference, rather than exploring the environmental and socioeconomic factors that have been shown to influence lung function. Lundy Brahn, a Brown University professor of Africana studies and medical science, addresses these issues in her article “Race, ethnicity and lung function: A brief history,” where she provides insights on how to address lung function research in the future.

“Research and clinical practice needs to devote more careful attention to the social nature of racial and ethnic categories and draw on more complex explanatory frameworks that incorporate disproportionate exposures to toxic environments, differential access to high-quality care and the daily insults of racism in every sphere of life that manifest biologically.”²

– Lundy Braun, PhD

Sources:

¹Spirometry: Mayo Clinic

https://www.mayoclinic.org/tests-procedures/spirometry/about/pac-20385201#:~:text=Spirometry%20is%20used%20to%20diagnose,is%20helping%20you%20breathe%20better.

²Race, ethnicity and lung function: A brief history, by Lundy Brahn

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4631137

³ Breathing race into the machine: The surprising career of the spirometer from plantation to genetics, by Lundy Braun

https://www.upress.umn.edu/book-division/books/breathing-race-into-the-machine

⁴Different ethnic standards for lung functions, or one standard for all?, by J.E. Myers

https://journals.co.za/content/m_samj/65/19/AJA20785135_10800

⁵Science reflects history as society influences science: brief history of “race,” “race correction,” and the spirometer, by Heidi L. Lujan and Stephen E. DiCarlo

https://journals.physiology.org/doi/full/10.1152/advan.00196.2017

⁶ The Science and Politics of Racial Research, by William H. Tucker

https://books.google.com/books/about/The_Science_and_Politics_of_Racial_Resea.html?id=OBsHSzmkYHkC

⁷Investigations in the Military and Anthropological Statistics of American Soldiers, by Benjamin Apthorp Gould

https://archive.org/details/investigationsi00goulgoog/page/n26/mode/2up

⁸Defining race/ethnicity and explaining difference in research studies on lung function, by Lundy Braun

https://erj.ersjournals.com/content/41/6/1362

⁹Racial basis for asbestos lawsuits?; Owens Corning seeks more stringent standards for blacks, by Erin Texeira

https://www.baltimoresun.com/news/bs-xpm-1999-03-25-9903250041-story.html