Proper Self-collection of Nasal Swabs Critical for Accurate COVID-19 Testing
As the number of nationwide COVID-19 cases begins to climb again, the U.S. Food and Drug Administration (FDA) has called upon healthcare providers to give clear, step-by-step instructions to patients who self-collect nasal samples for SARS-CoV-2 testing in healthcare settings, such as clinics and other testing sites.
Self-collected nasal swabs can make testing less invasive and more tolerable for patients than swabs taken by healthcare workers from the back of the nose (nasopharyngeal or NP swabs). For healthcare workers, self-collected nasal swabs can lower the risk of exposure to SARS-CoV-2, the virus that causes COVID-19. Healthcare workers can maintain at least 6 feet of separation from patients, which can help reduce the use of personal protective equipment and preserve limited supplies, according to the FDA.
But without proper instructions, patients may not collect an adequate sample for testing. Samples that are not collected correctly may not contain a sufficient amount of the virus (if present) to be detected, says FDA recommendations issued on October 7, 2020. Without proper sample collection, the test may give false-negative results and indicate that the patient is not infected, when, in fact, they are infected. “Health care providers have a critical role in helping patients perform self-collection accurately,” the recommendations say.
Those recommendations call upon healthcare providers to personally give step-by-step explanations of how to effectively collect nasal samples to patients. In addition, the FDA recommends providers give patients written or video instructions. In particular, healthcare providers should instruct patients to:
- Put the entire swab tip inside the nose and rub the side of the swab with moderate pressure against as much of the wall of the nostril—also called the anterior nares—as possible.
- Make four to five sweeping circles with the same swab in each nostril, for about 10-15 seconds per nostril. Both nostrils should be swabbed so that a sufficient sample is collected.
- Simply twirling the swab against one part of the inside of the nose or leaving the swab in the nose for 10-15 seconds is not proper technique and may result in an insufficient sample.
The recommendations also emphasize using the appropriate type of swab. Patients should only use the swab that they are provided and not substitute it with any other swab. Nasopharyngeal swabs and oropharyngeal specimens from the throat just behind the mouth are not appropriate for self-collection, the FDA adds.
The recommendations cite evidence that nasal specimens from the nostrils provide similar information to those from the back of the nose and throat, as long as the specimen is of good quality. Evidence comes from a French study of molecular detection of SARS-CoV-2 that found use of nasal swab specimens was nearly equivalent to the detection using nasopharyngeal swabs, which are considered to be the gold standard. SARS-CoV-2 detection from nasal samples showed high sensitivity and specificity. A U.S. study of 498 patients who both took their own nasal swabs and had nasopharyngeal swabs done by a healthcare professional reached a similar conclusion.
The FDA recommendations apply specifically to patients who are self-collecting in a healthcare setting. The FDA has approved some test kits that use samples that are self-collected by patients at home and then sent to a lab for testing. Patients who use these home-collection kits must follow the instructions for those specific test kits.
Recommendations on Providing Clear Instructions to Patients Who Self-Collect an Anterior Nares (Nasal) Sample in a Health Care Setting for SARS-CoV-2 Testing – Letter to Health Care Providers. Food and Drug Administration. Available online at https://www.fda.gov/medical-devices/letters-health-care-providers/recommendations-providing-clear-instructions-patients-who-self-collect-anterior-nares-nasal-sample?utm_medium=email&utm_source=govdelivery. Published October 7, 2020. Accessed October 13, 2020.
Péré H, Podglajen I, Wack M, et al. Nasal Swab Sampling for SARS-CoV-2: a Convenient Alternative in Times of Nasopharyngeal Swab Shortage. Journal of Clinical Microbiology. Available online at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7269411/ . Published May 26, 2020. Accessed October 19, 2020.
Yuan-Po Tu et al. Swabs Collected by Patients or Health Care Workers for SARS-CoV-2 Testing. New England Journal of Medicine. Available online at https://www.nejm.org/doi/full/10.1056/NEJMc2016321. Published July 30, 2020. Accessed October 19, 2020.