Frontline Screening for SARS-CoV-2 Infection at Emergency Department Admission by Third Generation Rapid Antigen Test: Can We Spare RT-qPCR?

Abstract

To complement RT-qPCR testing for diagnosis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections, many countries have introduced the use of rapid antigen tests. As they generally display lower real-life performances than expected, their correct positioning as frontline screening is still controversial. Despite the lack of data from daily clinical use, third generation microfluidic assays (such as the LumiraDx SARS-CoV-2 Ag test) have recently been suggested to have similar performances to RT-qPCR and have been proposed as alternative diagnostic tools. By analyzing 960 nasopharyngeal swabs from 960 subjects at the emergency department admissions of a tertiary COVID-19 hospital, LumiraDx assay demonstrated a specificity of 97% (95% CI: 96–98), and a sensitivity of 85% (95% CI: 82–89) in comparison with RT-qPCR, which increases to 91% (95% CI: 86–95) for samples with a cycle threshold ≤ 29. Fifty false-negative LumiraDx-results were confirmed by direct quantification of genomic SARS-CoV-2 RNA through droplet-digital PCR (median (IQR) load = 5880 (1657–41,440) copies/mL). Subgenomic N and E RNAs were detected in 52% (n = 26) and 56% (n = 28) of them, respectively, supporting the presence of active viral replication. Overall, the LumiraDx test complies with the minimum performance requirements of the WHO. Yet, the risk of a misrecognition of patients with active COVID-19 persists, and the need for confirmatory RT-qPCR should not be amended.

Diagnostic, Prognostic, and Therapeutic Value of Droplet Digital PCR (ddPCR) in COVID-19 Patients: A Systematic Review

“…An overall of 3651 samples, from 2825 patients and 145 controls, were extracted from the 39 included studies. The studies were conducted worldwide; 16 in Asia [ 12 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ], 14 in Europe [ 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 ], and 9 in North America [ 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 ]. A minority of studies (8) included control samples [ 21 , 28 , 29 , 33 , 38 , 47 , 54 , 56 ].…”

“…Whereas most studies contrasted the performance of ddPCR with RT-qPCR, a few used a different comparison tool. For instance, a study compared ddPCR with LumiraDx rapid antigen testing, with the former showing superior diagnostic accuracy by detecting false-negative results of the latter [ 36 ].…”

Sequential coupling of dry and wet COVID-19 screening to reduce the number of quarantined individuals

“…We used the digital checker designed by the US CDC (Sensitivity: 0.94; Specificity: 0.29). 3 For the RATs, we utilized one reported by Cento et al from Italy (Sensitivity: 0.85; Specificity: 0.97) as RAT 1, 4 and the other reported by Kim et al from Korea (Sensitivity: 0.90; Specificity: 0.98) 5 as RAT 2. We further hypothesized two scenarios: RAT only and RAT plus digital checker (digital checker as the first-stage screening test).…”

SARS-CoV-2 microfluidic antigen point-of-care testing in Emergency Room patients during COVID-19 pandemic

“…A new generation of POCT for SARS-CoV-2 antigen based on the microfluidic technology integrating sample preparation, reaction and detection into a miniaturized chip ( Whitesides, 2006 ) has recently demonstrated a significant higher sensitivity compared with lateral flow POCT ( Bianco et al, 2021 ; Cento et al, 2021 ; Dinnes et al, 2021 ; Drain et al, 2021 ; Kohmer et al, 2021 ).…”

“…This turns crucial when ER are overwhelmed during the epidemic phase. However, major concern is the false-negative rate due to low viral load ( Arons et al, 2020 ; Cento et al, 2021 ; Orsi et al, 2021 ) for antigen testing. A new generation of microfluidic-based POCT recently demonstrated a higher sensitivity than later flow immunochromatography-based POCT ( Bianco et al, 2021 ; Dinnes et al, 2021 ; Drain et al, 2021 ; Kohmer et al, 2021 ; Orsi et al, 2021 ; Toptan et al, 2021 ).…”