Evaluation of accuracy, exclusivity, limit-of-detection and ease-of-use of LumiraDx™: An antigen-detecting point-of-care device for SARS-CoV-2

Abstract

Purpose Rapid antigen-detecting tests (Ag-RDTs) for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can transform pandemic control. Thus far, sensitivity (≤ 85%) of lateral-flow assays has limited scale-up. Conceivably, microfluidic immunofluorescence Ag-RDTs could increase sensitivity for SARS-CoV-2 detection. Methods This multi-centre diagnostic accuracy study investigated performance of the microfluidic immunofluorescence LumiraDx™ assay, enrolling symptomatic and asymptomatic participants with suspected SARS-CoV-2 infection. Participants collected a supervised nasal mid-turbinate (NMT) self-swab for Ag-RDT testing, in addition to a professionally collected nasopharyngeal (NP) swab for routine testing with reverse transcriptase polymerase chain reaction (RT-PCR). Results were compared to calculate sensitivity and specificity. Sub-analyses investigated the results by viral load, symptom presence and duration. An analytical study assessed exclusivity and limit-of-detection (LOD). In addition, we evaluated ease-of-use. Results The study was conducted between November 2nd 2020 and 4th of December 2020. 761 participants were enrolled, with 486 participants reporting symptoms on testing day. 120 out of 146 RT-PCR positive cases were detected positive by LumiraDx™, resulting in a sensitivity of 82.2% (95% CI 75.2–87.5%). Specificity was 99.3% (CI 98.3–99.7%). Sensitivity was increased in individuals with viral load ≥ 7 log10 SARS-CoV2 RNA copies/ml (93.8%; CI 86.2–97.3%). Testing against common respiratory commensals and pathogens showed no cross-reactivity and LOD was estimated to be 2–56 PFU/mL. The ease-of-use-assessment was favourable for lower throughput settings. Conclusion The LumiraDx™ assay showed excellent analytical sensitivity, exclusivity and clinical specificity with good clinical sensitivity using supervised NMT self-sampling. Trial registration number and registration date DRKS00021220 and 01.04.2020

Evaluation of the Practicability of Biosynex Antigen Self-Test COVID-19 AG+ for the Detection of SARS-CoV-2 Nucleocapsid Protein from Self-Collected Nasal Mid-Turbinate Secretions in the General Public in France

“…Finally, the performances of supervised self-collected specimens for detection of SARS-CoV-2 using a WHO-listed SARS-CoV-2 Ag-RDT was evaluated in adult volunteers in Charité hospital, Universitätsmedizin Berlin, Germany [ 12 , 13 , 14 , 15 ]. Thus, nasal sampling (including self-sampling) assessed against nasopharyngeal sampling led to comparable performance using SARS-CoV-2 Ag-RDT [ 12 , 13 , 15 ].…”

“…Finally, the performances of supervised self-collected specimens for detection of SARS-CoV-2 using a WHO-listed SARS-CoV-2 Ag-RDT was evaluated in adult volunteers in Charité hospital, Universitätsmedizin Berlin, Germany [ 12 , 13 , 14 , 15 ]. Thus, nasal sampling (including self-sampling) assessed against nasopharyngeal sampling led to comparable performance using SARS-CoV-2 Ag-RDT [ 12 , 13 , 15 ]. Klein and colleagues extended these studies by evaluating the clinical performances of a supervised, self-collected NMT swab and a professional-collected naso-pharyngeal swab, using Panbio™ Ag-RDT (distributed by Abbott) by reference to molecular testing [ 14 ].…”

“…Alternative sampling methods, such as nasal mid-turbinate (NMT) sampling (swab inserted about 2–3 cm into nostril parallel to the palate until resistance is met at turbinates), is well tolerated and can be performed by the person himself either unsupervised at home or supervised on-site [ 10 , 11 , 12 , 13 ]. NMT sampling was equivalent to nasopharyngeal sampling for a WHO-listed SARS-CoV-2 Ag-RDT, which lays the foundation for its use as a self-sampling technique under supervision [ 12 , 13 , 14 , 15 ]. Widespread use of self-testing for SARS-CoV-2 infection could help improve the control of the spread of the SARS-CoV-2 epidemic [ 16 , 17 , 18 , 19 , 20 , 21 ].…”

Screening for SARS-CoV-2 in close contacts of individuals with confirmed infection: performance and operational considerations

“…Study staff responsible for use of the antigen tests were invited to participate in a usability assessment. A System Usability Scale (SUS) was employed, and an Ease of Use (EoU) questionnaire was adapted [21,28] (Supplementary Material D). SUS scores above 68 were considered acceptable [29,30].…”

“…SUS scores above 68 were considered acceptable [29,30]. To analyze data from the EoU questionnaire, a matrix was used to rank aspects of the products’ usability as “satisfactory,” “average,” or “unsatisfactory” (Supplementary Material E) [21].…”