Test samples collected by people who swabbed their own nasal passages yielded results for the COVID-19 virus that were as accurate as samples collected by a health care worker, according to a small study by researchers at the Stanford University School of Medicine.
The 30 study participants, who previously had tested positive for COVID-19, collected their own samples at a drive-through testing site after watching a short video animation and reading a one-page document instructing them how to perform the swab. The nasal swab for the study is more comfortable to use than the long nasopharyngeal swab currently used to collect samples from the back of the nasal cavity.
Allowing people who suspect they may have COVID-19 to collect their own sample has many advantages. Sample-collection kits could be widely distributed, allowing more people to be tested. Those using the kit wouldn't have to travel to a testing site, negating the risk of transmission to health care workers and others with whom they interact in transit. Self-collection would also conserve supplies of personal protective equipment used by health care workers.
"There is an urgent need to increase our testing capacity to slow the overall spread of the virus," said Dr Yvonne Maldonado, professor of paediatric infectious diseases and of health research and policy. "A sample collection procedure that can safely and easily be performed by the patient in their own car or at home could reduce the exposure of health care workers and also allow many more people to submit samples for testing."
Maldonado is the senior author of the study, which was conducted in collaboration with Dr Andra L Blomkalns, the Redlich Family professor and professor and chair of emergency medicine, and Dr Prasanthi Govindarajan, associate professor of emergency medicine; senior research data analyst Jonathan Altamirano is the lead author.
The study participants had tested positive in March at Stanford Health Care for the virus that causes COVID-19. Maldonado and her team contacted each of them by phone at home and provided them with written instructions and a short video about how to collect a nasal swab.
They were asked to return to Stanford Health Care for drive-through testing. At that visit, they collected their own specimen by applying a nasal swab to both nostrils. Then, a physician collected two additional samples using a nasal swab and a swab applied to the back of the throat and the tonsils. All three samples were tested for the presence of the virus at the Stanford Clinical Virology Laboratory.
Of the 30 participants, 29 received identical results – either positive or negative for the presence of the virus – for the three samples. Eleven of the participants were positive, and 18 were negative. One person's self-collected swab at the drive-through site revealed the presence of the virus, whereas the two swabs collected by the physician tested negative.
The researchers were also interested in learning how long an infected person would test positive for the virus after they first experienced symptoms. Twenty-three participants reported that they first experienced symptoms between four and 37 days prior to returning for the drive-through test. (The timing of symptom onset was unavailable for seven of the participants.) Of the 12 people who returned within two weeks after symptoms began, seven tested positive; of the 11 people who returned for testing more than two weeks after symptom onset, only two tested positive.
"It is critical for us to understand how long an infected person may remain infectious and what the pattern of transmission might be within their household," Maldonado said. "This information would help public health workers craft guidelines as to how long a person with COVID-19 should remain quarantined and when it is likely to be safe to interact again with family members and co-workers. Understanding the timeline of viral shedding will be particularly important for previously infected health care workers who are needed to care for other COVID-19 patients."
Abstract
Introduction: Since the emergence of the sudden acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreak in Wuhan, China, in December 2019, the virus has spread to 173 countries, resulting in 3 855 788 confirmed cases and 265 862 deaths as of May 9, 2020.1 Stanford Health Care was one of the first nonfederal facilities to obtain US Food and Drug Administration approval for a proprietary test using reverse transcriptase–polymerase chain reaction for SARS-CoV-2 using nasopharyngeal and oropharyngeal specimens on March 2, 2020. However, specimen collection must be done by health care workers and requires extensive use of personal protective equipment. To minimize the risk of exposure during testing, reduce personal protective equipment use, and increase access to testing, we compared the diagnostic equivalence of a modified specimen collection method, patient-collected lower nasal swabs, with that of the current clinical standard, health care worker–collected oropharyngeal swabs. If the 2 methods proved to be diagnostically equivalent, patients would be able to collect specimens themselves without exposing health care workers to respiratory secretions.
Methods: This prognostic study was approved by the Stanford University institutional review board. Participants provided oral informed consent to clinical research coordinators and then signed a consent form with the physician who collected the oropharyngeal swab. This study complies with the Standards for Reporting of Diagnostic Accuracy (STARD) reporting guideline.
The target population was Stanford Health Care outpatients with a reverse transcriptase–polymerase chain reaction test that was positive for SARS-CoV-2 in March 2020. We included a convenience sample of patients who consented to be contacted by our study staff. Our study staff obtained informed consent remotely, to minimize exposure of research staff to infected patients and to reduce the duration of study visits, and sent instructional materials electronically. Health care workers were excluded because of their familiarity with specimen collection, as were patients enrolled in drug trials for SARS-CoV-2.
After informed consent was obtained, participants were scheduled to return to Stanford Health Care for drive-through collection of 3 specimens using a patient-collected lower nasal swab (Puritan Sterile Foam Tipped Applicator; Puritan Medical Products), a physician-collected lower nasal swab (Puritan Sterile Foam Tipped Applicator; Puritan Medical Products), and a physician-collected oropharyngeal swab (FLOQ Swabs; Copan Diagnostics). During the visit, participants received a $20 incentive. The 3 specimens were placed in separate 3-mL tubes of viral transport medium (M4RT Transport; Remel MicroTest), stored in a cooler, and delivered to the Stanford Clinical Virology Laboratory. Specimens were tested for SARS-CoV-2 using reverse transcriptase–polymerase chain reaction targeting the envelope or open reading frame 1 ab genes.2,3
We report participant demographic characteristics, sensitivity and specificity, and discordant probabilities with 95% binomial CIs of patient-collected lower nasal compared with physician-collected oropharyngeal specimens. All analyses were performed with SAS statistical software version 9.4 (SAS Institute). Data analysis was performed in May 2020.
Results: Of 129 eligible SARS-CoV-2–infected patients, 30 participated in the study (mean [SD] age, 48.2 [16.0] years; 16 men [53%]). We do not have reasons for refusal for nonparticipants. Participants were predominantly white (20 participants [66%]), with no sex or age group predominance. Twelve participants (40%) self-reported possible exposure to SARS-CoV-2. Cough (20 participants [67%]), fever (13 participants [43%]), and sore throat (8 participants [27%]) were commonly reported symptoms during the first visit. Approximately one-half of the participants had documentation of chronic medical conditions (16 participants [53%]), and 5 participants (17%) tested positive for coinfections with other respiratory viruses (Table 1).
We observed diagnostic equivalence across the 3 methods of specimen collection (Table 2). Eleven participants (37%) had test results that were positive for SARS-CoV-2 across patient- and physician-collected specimens, and 18 participants (60%) had results that were negative for SARS-CoV-2 across patient- and physician-collected specimens. The only discordant result was a participant whose self-collected nasal specimen tested positive, whereas both of their physician-collected specimens tested negative (3.30%; 95% CI, 0.08%-17.00%). The sensitivity of the patient-collected specimens was 100% (95% CI, 72%-100%), and the specificity was 95% (95% CI, 74%-100%).
Discussion: These findings contribute to the recently released US Food and Drug Administration guidance4 that lists patient-collected lower nasal swab as an acceptable specimen collection method for SARS-CoV-2 testing. Self-collected lower nasal swabs could also be used for home- or office-based testing of asymptomatic patients. However, these preliminary findings are limited by small sample size, have limited generalizability, and need to be validated further in diverse clinical settings. These validation efforts are currently under way at our institution.
Authors
Jonathan Altamirano, Prasanthi Govindarajan, Andra L Blomkalns, Lauren E Kushner, Bryan Andrew Stevens, Benjamin A Pinsky, Yvonne Maldonado
[link url="http://med.stanford.edu/news/all-news/2020/06/self-swabbing-tests-for-covid-19-accurate-and-safe.html"]Stanford Medicine material[/link]
[link url="https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2767065"]JAMA Network Open abstract[/link]