COVID-19 Evidence Alerts
from McMaster PLUSTM

Current best evidence for clinical care (more info)

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Diagnosis Drain PK, Ampajwala M, Chappel C, et al. A Rapid, High-Sensitivity SARS-CoV-2 Nucleocapsid Immunoassay to Aid Diagnosis of Acute COVID-19 at the Point of Care: A Clinical Performance Study. Infect Dis Ther. 2021 Feb 24. pii: 10.1007/s40121-021-00413-x. doi: 10.1007/s40121-021-00413-x.

INTRODUCTION: The LumiraDx severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigen test, which uses a high-sensitivity, microfluidic immunoassay to detect the nucleocapsid protein of SARS-CoV-2, was evaluated for diagnosing acute coronavirus disease 2019 (COVID-19) in adults and children across point-of-care settings (NCT04557046).

METHODS: Two paired anterior nasal swabs or two paired nasopharyngeal swabs were collected from each participant. Swabs were tested by the LumiraDx SARS-CoV-2 antigen test and compared with real-time polymerase chain reaction (rt-PCR; Roche cobas 6800 platform). Sensitivity, specificity and likelihood ratios were calculated. Results were stratified on the basis of gender, age, duration of symptoms, and rt-PCR cycle threshold.

RESULTS: Out of the 512 participants, aged 0-90 years, of this prospective validation study, 414 (81%) were symptomatic for COVID-19 and 123 (24%) swabs were positive for SARS-CoV-2 based on rt-PCR testing. Compared with rt-PCR, the 12-min nasal swab test had 97.6% sensitivity and 96.6% specificity, and nasopharyngeal swab had 97.5% sensitivity and 97.7% specificity, within 12 days of symptom onset, representing the period of infectivity. All (100%) samples detected within 33 rt-PCR cycles were also identified using the antigen test. Results were consistent across age and gender. The user error rate of the test system when used by minimally trained operators was 0.7% (95% confidence interval [CI] 0.1-3.7%).

CONCLUSION: The rapid, high-sensitivity assay using nasopharyngeal or anterior nasal sampling may offer significant improvements for diagnosing acute SARS-CoV-2 infection in clinic- and community-based settings.

Discipline / Specialty Area Score
Hospital Doctor/Hospitalists
Internal Medicine
Public Health
Pediatric Neonatology
Pediatric Emergency Medicine
Emergency Medicine
Infectious Disease
Pediatrics (General)
Comments from MORE raters

Emergency Medicine rater

This study looked at the LumiraDx rapid antigen for SARS-CoV-2. The performance characteristic, when compared against rt-PCR with sensitivity of approximately 97% sensitivity and 98 specificity either performed as a nasal swab (anterior nose) or as a nasopharyngeal swab. The performance characteristic was true regardless of age or sex. This takes only 12 min and was able to be performed successfully by people with minimal training. These testing characteristic makes this a great choice for testing/screening in those with suspected COVID-19 with a quick turnaround time and an alternative to rt-PCR. However one thing to consider is that this does require its proprietary extraction buffer, and the typical viral transport media that is normally used for other testing. Regardless, it is important to have another accurate test as testing supplies continue to remain limited.

Emergency Medicine rater

Industry-sponsored preliminary diagnostic accuracy study for a point-of-care antigen test with sensitivity/specificity consistent between genders and age groups with an acceptable user-error rate. This study design addresses many of the diagnostic biases identified in SARS-CoV-2 diagnostic research (, but requires external (preferably non-industry sponsored) validation before confident extrapolation to other settings is possible.

Hospital Doctor/Hospitalists rater

Good study! Well-written article that's also easy to read.

Infectious Disease rater

I am not an expert on the various diagnostic testing methodologies, but this looks promising.

Pediatric Emergency Medicine rater

This study demonstrates excellent test characteristics of the point of care SARS-CoV2 test studied in symptomatic patients. This would suggest this test, if available, would be a good alternative to PCR testing in symptomatic patients.

Pediatric Neonatology rater

It's hard to tell if there were any neonates in the study. However, the rapid screening method might be useful in NICU for screening staff, parents, visitors, etc. They cross-checked with "16" viruses. I hope these included endemic Corona virus. Also, shedding N protein may not be as indicative of infectivity as they claim. Shedding Ag does not always mean infective.

Pediatric Neonatology rater

Need of the hour. Very high sensitivity and specificity. The antigen test has a run time of only 12 minutes compared with the longer time of > 6 hours for RT-PCR. Although the costs of the tests were not mentioned in the study, it is assumed antigen testing will be cheaper than the RT-PCR test.

Pediatrics (General) rater

A new direct antigen test for Covid with great sensitivity and specificity.

Public Health rater

I have never rated a R=7 and N=7 before. I work 6 days a week testing and vaccinating in the field. This article makes me believe there is a test that is rapid that works. All I can say is "praise be" because half the crowd goes to a fly-by-night test site and wants treatment and/or vaccination based on it. Sigh.