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Is a novel 3-dimensionally printed nasopharyngeal swab (3DP swab) accurate in detecting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)?
In this diagnostic study for coronavirus disease 2019 (COVID-19) across 2 institutions of 79 patients with COVID-19 and 10 controls, the overall agreement and positive percentage agreement of the 3DP swab was 91.1% and 93.5%, respectively, compared with the traditional FLOQSwab (COPAN Diagnostics) and Dacron swab (Deltalab). The positive percentage agreement was 100% for COVID-19 cases tested within the first week of illness, and reverse-transcriptase polymerase chain reaction cycle threshold values for the ORF1ab and E-gene targets showed a strong correlation between the 3DP and traditional swab on independent testing at each institution despite differences in sample processing.
The 3DP swab performed accurately and consistently across health care institutions and may help mitigate strained resources in the escalating COVID-19 pandemic.
Three-dimensionally printed nasopharyngeal swabs (3DP swabs) have been used to mitigate swab shortages during the coronavirus disease 2019 (COVID-19) pandemic. Clinical validation for diagnostic accuracy and consistency, as well as patient acceptability, is crucial to evaluate the swab’s performance.
To determine the accuracy and acceptability of the 3DP swab for identifying severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).
Design, Setting, and Participants
A diagnostic study was conducted from May to July 2020 at 2 tertiary care centers in Singapore with different reference swabs (FLOQSwab [COPAN Diagnostics] or Dacron swab [Deltalab]) and swab processing techniques (wet or dry) to evaluate the performance of the 3DP swab compared with traditional, standard-of-care nasopharyngeal swabs used in health care institutions. The participants were patients with COVID-19 in the first 2 weeks of illness and controls with acute respiratory illness with negative test results for SARS-CoV-2. Paired nasopharyngeal swabs were obtained from the same nostril and tested for SARS-CoV-2 by reverse-transcriptase polymerase chain reaction. The sequence of swabs was randomized based on odd and even participant numbers.
Main Outcomes and Measures
Primary outcome measures were overall agreement (OA), positive percentage agreement (PPA), and negative percentage agreement of the 3DP swab compared with reference swabs. Secondary outcome measures were the correlation of cycle threshold (Ct) values of both swabs.
The mean (SD) age of participants was 45.4 (13.1) years, and most participants were men (87 of 89 [97.8%]), in keeping with the epidemiology of the COVID-19 pandemic in Singapore. A total of 79 patients with COVID-19 and 10 controls were recruited. Among the patients with COVID-19, the overall agreement and PPA of the 3DP swab was 91.1% and 93.5%, respectively, compared with reference swabs. The PPA was 100% for patients with COVID-19 who were tested within the first week of illness. All controls tested negative. The reverse-transcriptase polymerase chain reaction Ct values for the ORF1ab and E-gene targets showed a strong correlation (intraclass correlations coefficient, 0.869-0.920) between the 3DP and reference swab on independent testing at each institution despite differences in sample processing. Discordant results for both gene targets were observed only at high Ct values.
Conclusions and Relevance
In this diagnostic study of 79 patients with COVID-19 and 10 controls, the 3DP swab performed accurately and consistently across health care institutions and could help mitigate strained resources in the escalating COVID-19 pandemic.
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Accepted for Publication: December 22, 2020.
Published Online: February 18, 2021. doi:10.1001/jamaoto.2020.5680
Corresponding Author: David M. Allen, MD, Division of Infectious Diseases, Department of Medicine, National University of Singapore, 1E Kent Ridge Rd, Singapore 119228 (email@example.com).
Author Contributions: Drs Tay and Allen had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis. Drs Tay and Dr Cross are equal contributors.
Concept and design: Tay, Cross, Toh, J. Loh, Z. Lim, W. Chow, Goh, Siow, K. Loh, Chua, H. Tan, Chan, Wang, Fuh, Yen, Wong, Allen.
Acquisition, analysis, or interpretation of data: Tay, Cross, Toh, Lee, J. Loh, Z. Lim, Ngiam, Chee, Gan, Saraf, Lian, W. Loh, C. Lim, T. Tan, Yan, Ko, Oon, V. Chow, Wang, Allen.
Drafting of the manuscript: Tay, Cross, Toh, Z. Lim, Chee, Gan, Saraf, Yan, Chan, Yen, Allen.
Critical revision of the manuscript for important intellectual content: Tay, Cross, Toh, Lee, J. Loh, Ngiam, Chee, W. Chow, Goh, Siow, Lian, W. Loh, K. Loh, C. Lim, Chua, T. Tan, H. Tan, Ko, Oon, V. Chow, Wang, Fuh, Yen, Wong, Allen.
Statistical analysis: Tay, Z. Lim, Ko, V. Chow.
Obtained funding: K. Loh, Wong.
Administrative, technical, or material support: Cross, Toh, Lee, J. Loh, Z. Lim, Ngiam, Chee, W. Chow, Goh, Siow, Lian, K. Loh, Chua, H. Tan, Chan, V. Chow, Wang, Fuh, Yen, Wong.
Supervision: Cross, K. Loh, Yan, Chan, V. Chow, Wang, Yen, Wong, Allen.
Other - Conduct of the trial: Cross.
Other - conduct experiment: Gan.
Other - mechanical testing: Saraf.
Other - SGH data: Ko.
Conflict of Interest Disclosures: Dr Yen and Mr Chow reported a patent filed by the National University of Singapore describing the design of the 3-dimensionally printed nasopharyngeal swab reported in this article. All clinical aspects of the study (clinical testing, analysis and interpretation) were performed independently from the swab design team, including Dr Yen and Mr Chow. No other disclosures were reported.
Funding/Support: This study was supported in part by the National Medical Research Council, Singapore (grant NMRC/CIRG18nov-0045) and the National Research Foundation, Singapore under its International Research Centres in Singapore Funding Initiative.
Role of the Funder/Sponsor: The funding organizations had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.
Disclaimer: Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not reflect the views of National Medical Research Council or the National Research Foundation, Singapore.
Additional Contributions: We acknowledge the support of our medical colleagues and patient participants during the clinical study, as well as the National University Hospital Operating Theatre for their support in sterilizing the 3DP swabs. We thank Paul A. Tambyah, MD, for advice on the study design. We thank Chaw Sing Ho, PhD, and the National Additive Manufacturing Innovation Cluster Singapore for their coordinating efforts between stakeholders and regulatory agencies. Images of the final swab were also contributed by Eye-2-Eye Communications and Structo. Data from the mechanical testing was kindly provided by TÜV SÜD PSB Singapore.
Additional Information: The data shown in this article are available on request from the corresponding author. Anonymized cycle threshold values and day of illness for the clinical validation study are included in eMethods in the Supplement.
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