COVID-19 Evidence Alerts
from McMaster PLUSTM

Current best evidence for clinical care (more info)

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Diagnosis Masia M, Fernandez-Gonzalez M, Sanchez M, et al. Nasopharyngeal Panbio COVID-19 Antigen Performed at Point-of-Care Has a High Sensitivity in Symptomatic and Asymptomatic Patients With Higher Risk for Transmission and Older Age. Open Forum Infect Dis. 2021 Feb 2;8(3):ofab059. doi: 10.1093/ofid/ofab059. eCollection 2021 Mar.

Background: Performance of point-of-care tests in different clinical scenarios and on different samples remains undetermined. We comprehensively evaluated the performance of the nasopharyngeal Panbio COVID-19 Ag Rapid Test Device.

Methods: This is a prospective study that includes consecutive patients attending 3 primary care centers (PCCs) and an emergency department. The antigen test was performed at point-of-care in nasopharyngeal and nasal swabs and in saliva. Positive percent agreement (PPA) and negative percent agreement (NPA) were calculated with the reverse-transcription polymerase chain reaction (RT-PCR) assay as reference standard.

Results: Of 913 patients included, 296 (32.3%) were asymptomatic and 690 (75.6%) came from the PCC. Nasopharyngeal swabs were collected from 913 patients, nasal swabs were collected from 659 patients, and saliva was collected from 611 patients. The RT-PCR was positive in 196 (21.5%) nasopharyngeal samples (NPS). Overall, PPA (95% CI) in NPS was 60.5% (53.3-67.4), and it was lower in nasal swabs (44.7%) and saliva (23.1%). Test performance in NPS was largely dependent on the cycle threshold (Ct) in RT-PCR, with PPA of 94% for Ct =25 and 80% for Ct <30. In symptomatic patients, the PPA was 95% for Ct =25, 85% for Ct <30, and 89% for the symptom triad of fever, cough, and malaise. Performance was also dependent on age, with a PPA of 100% in symptomatic patients >50 years with Ct <25. In asymptomatic patients, the PPA was 86% for Ct <25. In all cases, NPA was 100%.

Conclusions: The nasopharyngeal Panbio COVID-19 Ag test performed at point-of-care has a good sensitivity in symptomatic patients with Ct <30 and older age. The test was useful to identify asymptomatic patients with lower Ct values.

Discipline / Specialty Area Score
Infectious Disease
Hospital Doctor/Hospitalists
Internal Medicine
Family Medicine (FM)/General Practice (GP)
General Internal Medicine-Primary Care(US)
Public Health
Emergency Medicine
Comments from MORE raters

General Internal Medicine-Primary Care(US) rater

If selected, I would ask commentator to put this study into context with recently published Cochrane review on Coronavirus test accuracy studies.

Internal Medicine rater

To increase the understandability, it would be better to convert the term "cycle threshold (Ct)" to an appropriate viral load equivalent. "The percent agreement of the antigen test and PCR was higher when the viral load in the sample is high." is more easy to interpret than "The percent agreement of the antigen test and PCR was higher when the Ct was &lt;25."

Public Health rater

The benefit of this article to me is that it provides evidence when I am asked to give an opinion or advice to my GP colleagues.