Panbio antigen rapid test is reliable to diagnose SARS-CoV-2 infection

Background

RT-qPCR is the current recommended laboratory method to diagnose SARS-CoV-2 acute infection, several factors such as requirement of special equipment, time consuming, high cost and skilled staff limit the use of these techniques. A more rapid and high-throughput method is essential.

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Methods

We analyzed clinical data and nasopharyngeal samples, collected during September 2020, from patients attended at the emergency department of a secondary hospital and in two primary healthcare centers in Madrid. The performance of the Panbio COVID-19 AG Rapid Test Device for the detection of SARS-CoV-2 antigen was compared to RT-qPCR.

Results

255 nasopharyngeal swabs, including 150 from the emergency department and 105 from primary helthcare centers, were tested. 184 patients were symptomatic (72.1 %). Amongst the 60 positive RT-qPCR samples, 40 were detected by the rapid antigen test, given an overall sensitivity of 73.3 %. All the samples detected positive with the rapid antigen test were also positive with RT-qPCR. The median cycle threshold was 23.28 (IQR 18.5–30.16). Patients with less than seven days onset of symptoms showed a higher viral load, and sensitivity for rapid antigen test (86.5 %), compared to those with more days (sensitivity of 53.8 %)(p < 0.004).

Conclusions

The rapid antigen test evaluated in this study showed a high sensitivity and specificity in samples obtained during the first week of symptoms and with high viral loads. This assay seems to be an effective strategy for controlling the COVID-19 pandemic for the rapid identification and isolation of SARS-CoV-2 infected patients.

Abbreviations: COVID-19, Coronavirus disease 2019; CT, cycle threshold; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; NP, nucleocapsid protein; LFA, lateral flow assay; FDA, Food and Drug Administration; RT- qPCR, real-time reverse transcription polymerase chain reaction; RDT, rapid diagnostic test
Keywords: Rapid antigen detection test, SARS-CoV-2, RT-PCR, Point-of-care testing, Lateral flow assay, COVID19
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1. Introduction

Ensuring accurate diagnosis is essential to limit the spread of SARS-CoV-2 and for the clinical management of COVID-19. Although real-time reverse transcription polymerase chain reaction (RT-qPCR) is the currently recommended laboratory method to diagnose SARS-CoV-2 acute infection, several factors such as requirement of special equipment, time consuming, high cost and skilled staff limit the use of these molecular techniques. A more rapid and high-throughput method is in growing demand.

Until now, the use of antigen detection tests alone had been ruled out and not recommended due to their low sensitivity . Previously in the first wave, several easy to perform rapid antigen detection tests were developed as the first line of diagnostic. However, the results obtained were not good enough.

 

Abstract

Background: Antigen-detecting rapid diagnostic tests (Ag-RDTs) for the detection of SARS-CoV-2 offer new opportunities for testing in the context of the COVID-19 pandemic. Nasopharyngeal swabs (NPS) are the reference sample type, but oropharyngeal swabs (OPS) may be a more acceptable sample type in some patients.

Methods: We conducted a prospective study in a single screening center to assess the diagnostic performance of the Panbio COVID-19 Ag Rapid Test (Abbott) on OPS compared with reverse-transcription quantitative PCR (RT-qPCR) using NPS during the second pandemic wave in Switzerland.

Results: 402 outpatients were enrolled in a COVID-19 screening center, of whom 168 (41.8%) had a positive RT-qPCR test. The oropharyngeal Ag-RDT clinical sensitivity compared to nasopharyngeal RT-qPCR was 81% (95%CI: 74.2-86.6). Two false positives were noted out of the 234 RT-qPCR negative individuals, which resulted in a clinical specificity of 99.1% (95%CI: 96.9-99.9) for the Ag-RDT. For cycle threshold values ≤ 26.7 (≥ 1E6 SARS-CoV-2 genomes copies/mL, a presumed cut-off for infectious virus), 96.3% sensitivity (95%CI: 90.7-99.0%) was obtained with the Ag-RDT using OPS.

Interpretation: Based on our findings, the diagnostic performance of the Panbio™ Covid-19 RDT with OPS samples, if taken by a trained person and high requirements regarding quality of the specimen, meet the criteria required by the WHO for Ag-RDTs (sensitivity ≥80% and specificity ≥97%) in a high incidence setting in symptomatic individuals.

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Panbio Nasopharyngeal Testt
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Introduction

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for the coronavirus disease 2019 (COVID-19), characterised mainly by fever, cough, sore throat, fatigue, joint and muscle pain and loss of smell and taste . It was first identified in Hubei province in Wuhan, China, in December 2019 and until now, it continues to be a significant health issue worldwide. Because there is no specific therapy or medication, early and accurate diagnosis is critical in preventing the spread of the disease [6,7]. In vitro diagnostics have long been recognised as a valuable tool for outbreak control and patient care [8].
The current gold standard diagnostic test for laboratory diagnosis of SARS-CoV-2 is nucleic acid amplification tests (NAAT); reverse transcription polymerase chain reaction (RT-PCR) to be specific [9]. The advantage this has over other tests is its high sensitivity due to the nucleic acid amplification step while also having a high specificity due to the specific primers used.
This is consistent with its purpose at referral centres, which is to advise clinical care of patients. However, since it can take several hours to obtain results from RT-PCR, it may be inappropriate to use during an emergency. It also requires costly technology and competent workers, both of which may not be accessible in remote health clinics, particularly in underdeveloped countries.
Rapid antigen test (RAT) kits have emerged as an important alternative tool to aid in the clinical diagnosis of COVID-19. RAT is based on immunochromatography, which employs antibodies spotted onto nitrocellulose membranes that interact with specific antigens from the patient sample. The antigen–antibody interaction can be visualised manually or by using an immunofluorescence machine reader. For the diagnosis of COVID-19, the target analyte is often the virus’ nucleocapsid protein. A similar strategy has been used for the rapid diagnosis of HIV, malaria, influenza and other diseases . It is a reasonably inexpensive and simple test with quick results that may be used for point-of-care testing .
The advantage of RAT is that the test is more accessible to patients. It also enables appropriate infection control measures to be instituted earlier which is important in a pandemic . However, a negative RAT result cannot rule out COVID-19 infection [12]. Patients with typical clinical presentation or close contacts of COVID-19 cases should undergo repeat testing .
For diagnosis of SARS-CoV-2, the World Health Organisation has recommended that a RAT kit needs to meet a minimum performance requirement of at least 80% sensitivity and 97% specificity compared with a NAAT reference assay to be used [14]. Studies regarding the diagnostic accuracy of RAT have produced a wide range of sensitivity.
The varied results may be due to the various study designs, manufacturer of the RAT kits, patient selection, types of specimens and the phase of illness at the point of sample collection. While research and development of RAT to detect SARS-CoV-2 continue, this systematic review and meta-analysis aims to provide an update on the diagnostic accuracy in terms of estimating the specificity and sensitivity of RAT kits in patients with suspected COVID-19.
Source :
1. NCBI

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