Recent Study Finds Nasopharyngeal (NP) Swabs Remain the Gold Standard for Diagnosis of COVID-19
April 28, 2021
Nasopharyngeal (NP) swabs are considered the highest-yield specimen type for diagnostic testing of upper respiratory viruses, including SARS-CoV-2, and the use of a flocked NP swab is considered the gold standard as referenced by the US FDA. However, due to the overwhelming need for testing and the initial shortage of flocked NP swabs, many other types of collections have been used for diagnosing COVID19.
The Journal of Clinical Microbiology recently published a study titled “Performance of Saliva, Oropharyngeal Swabs, and Nasal Swabs for SARS-CoV-2 Molecular Detection: a Systematic Review and Meta-analysis.” The new meta-analysis performed by Lee et al reviewed the tremendous amount of literature (included in PubMed, Google Scholar, medRxiv, and bioRxiv up to October 2020) surrounding specimen collections for the diagnosis of SARS-CoV-2 infection. They found over 1,250 unique citations where different specimen collections were analyzed. They were able to include in their final analysis: 25 citations for saliva, 11 for nasal swabs (NS), 6 for oropharyngeal swabs (OP), and 4 for OP/NS combination swab collections; all of which were compared to NP swabs.
Three specimen types showed lower % positives as compared to NP specimens: NS (82%), OP (84%), and saliva (88%), while the combination of the OP/NS collections matched NP performance (97%). While OP/NS specimens likely require a healthcare worker for collection, the authors suggest that additional studies are warranted to understand the acceptability of this dual sample type in adult and pediatric patients. The authors also found that studies using flocked nasal swabs had a slightly higher % positive detection in comparison to unflocked nasal swab studies.
Of note, NS studies which specified that both the NS and NP swabs were flocked, had a substantially higher % positive NS specimens than studies where an unflocked NS was compared to a flocked NP swab. This shows the superiority of flocked nylon swabs, like COPAN FLOQSwabs, to spun fiber swabs.
The authors conclude that nasopharyngeal swabs remain the gold standard for the diagnosis of SARS-CoV-2. And although alternative specimens are promising, much remains unknown about the impact of variations in specimen collection, specimen collectors, processing protocols, and the population tested. They suggest that head-to-head studies of sampling strategies are urgently needed using NP swabs as the benchmark.
“COPAN understands the important role proper sample collection plays in accurate diagnosis. We have considerably expanded our production capacity of nasopharyngeal flocked swabs to meet the increased demand for testing,” stated Norman Sharples, CEO of COPAN Diagnostics, Inc.
What Kind of Swabs are Suitable for COVID-19 Sample Collection?
As outlined in the CDC guidelines for the collection and handling of clinical specimens from patients suspected of being infected COVID-19, health care workers should only use synthetic fiber swabs with plastic shafts. * According to the FDA, “nasopharyngeal (NP) specimens are generally considered to yield the most sensitive test results” and “sample collection with a flocked swab, when available, is preferred” Both of the CDC and FDA recommendations are covered when using a COPAN NP FLOQSwabs®.
*Do not use calcium alginate swabs or swabs with wooden shafts when testing for COVID-19. These swabs can contain substances that inactivate some viruses and can inhibit PCR testing .
Click Here to learn more about COPAN’s flocked swabs
COPAN has compiled a COVID-19 resource page to facilitate answers to some of the frequently asked questions being received. Here you’ll find easy access to the evolving regulatory guidelines published by the CDC and FDA, COPAN’s distributor part numbers, and other resources about critical products that can be used for collecting, handling, and transporting specimens suspected of COVID-19.
Click Here to Go to the COVID-19 Resource Page for Coronavirus Products and Resources
- Performance of Saliva, Oropharyngeal Swabs, and Nasal Swabs for SARS-CoV-2 Molecular Detection: a Systematic Review and Meta-analysis, Rose A. Lee, Joshua C. Herigon, Andrea Benedetti, Nira R. Pollock, Claudia M. Denkinger, Journal of Clinical Microbiology Apr 2021, 59 (5) e02881-20; DOI: 10.1128/JCM.02881-20