Evaluation of Three Immunoassays for the Rapid Detection of SARS-CoV-2 antigens

Background Comprehensive information about the accuracy of antigen rapid diagnostic tests (Ag-RDTs) for SARS-CoV-2 is essential to guide public health decision makers in choosing the best tests and testing policies. In August 2021, we published a systematic review and meta-analysis about the accuracy of Ag-RDTs. We now update this work and analyze the factors influencing test sensitivity in further detail. Methods and findings We registered the review on PROSPERO (registration number: CRD42020225140). We systematically searched multiple databases (PubMed, Web of Science Core Collection, medRvix, bioRvix, and FIND) for publications evaluating the accuracy of Ag-RDTs for SARS-CoV-2 until August 31, 2021. Descriptive analyses of all studies were performed, and when more than 4 studies were available, a random-effects meta-analysis was used to estimate pooled sensitivity and specificity with reverse transcription polymerase chain reaction (RT-PCR) testing as a reference. To evaluate factors influencing test sensitivity, we performed 3 different analyses using multivariate mixed-effects meta-regression models. We included 194 studies with 221,878 Ag-RDTs performed. Overall, the pooled estimates of Ag-RDT sensitivity and specificity were 72.0% (95% confidence interval [CI] 69.8 to 74.2) and 98.9% (95% CI 98.6 to 99.1), respectively. When manufacturer instructions were followed, sensitivity increased to 76.4% (95%CI 73.8 to 78.8). Sensitivity was markedly better on samples with lower RT-PCR cycle threshold (Ct) values (sensitivity of 97.9% [95% CI 96.9 to 98.9] and 90.6% [95% CI 88.3 to 93.0] for Ct-values <20 and <25, compared to 54.4% [95% CI 47.3 to 61.5] and 18.7% [95% CI 13.9 to 23.4] for Ct-values ≥25 and ≥30) and was estimated to increase by 2.9 percentage points (95% CI 1.7 to 4.0) for every unit decrease in mean Ct-value when adjusting for testing procedure and patients symptom status. Concordantly, we found the mean Ct-value to be lower for true positive (22.2 [95% CI 21.5 to 22.8]) compared to false negative (30.4 [95% CI 29.7 to 31.1]) results. Testing in the first week from symptom onset resulted in substantially higher sensitivity (81.9% [95% CI 77.7 to 85.5]) compared to testing after 1 week (51.8%, 95% CI 41.5 to 61.9). Similarly, sensitivity was higher in symptomatic (76.2% [95% CI 73.3 to 78.9]) compared to asymptomatic (56.8% [95% CI 50.9 to 62.4]) persons. However, both effects were mainly driven by the Ct-value of the sample. With regards to sample type, highest sensitivity was found for nasopharyngeal (NP) and combined NP/oropharyngeal samples (70.8% [95% CI 68.3 to 73.2]), as well as in anterior nasal/mid-turbinate samples (77.3% [95% CI 73.0 to 81.0]). Conclusion Ag-RDTs detect most of the individuals infected with SARS-CoV-2, and almost all when high viral loads are present (>90%). With viral load, as estimated by Ct-value, being the most influential factor on their sensitivity, they are especially useful to detect persons with high viral load who are most likely to transmit the virus. To further quantify the effects of other factors influencing test sensitivity, standardization of clinical accuracy studies and access to patient level Ct-values and duration of symptoms are needed.

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Section: Discussionsupporting

confidence: 59%

“…In concordance with the above, many studies reporting an unusually low sensitivity performed the Ag-RDT not as per IFU [26, 28, 40, 66, 97, 108, 133, 184] or used saliva samples [20, 150, 155, 219]. However, 2 studies with IFU-conforming testing procedure on NP or AN/MT sample, still showed a low sensitivity.…”

Section: Discussionmentioning

confidence: 52%

Accuracy of rapid point-of-care antigen-based diagnostics for SARS-CoV-2: an updated systematic review and meta-analysis with meta regression analyzing influencing factors

Brümmer

Katzenschlager

McGrath

et al. 2022

Preprint

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“…for samples with PCR-positive Ct value of ≤25, whereas in samples with PCR-positive Ct value of >30, the sensitivity decreased to 0.0%. 30 In a longitudinal study of 43 adults newly infected with SARS-CoV-2, daily screening using LF-IFA for the SARS-CoV-2 N antigen can achieve approximately 90% sensitivity for individuals when they are viral culture positive. 31 Using MF-IFA for the SARS-CoV-2 N antigens, Lisa et al found that 120 of 146 PCR-positive cases were detected to be positive, which showed that the MF-IFA had a sensitivity of 82.19% and a specificity of 99.35%.…”

Section: Ta B L E 2 (Continued)mentioning

confidence: 99%

The utility of SARS‐CoV‐2 nucleocapsid protein in laboratory diagnosis

Xiong

Deng

et al. 2022

Clinical Laboratory Analysis

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By the end of December 2019, several unknown pneumonia cases who manifested as respiratory syndromes and fever were found in Wuhan, China. 1 Subsequently, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a novel virus classified as β-coronavirus genus, was identified in bronchoalveolar lavage fluid and other respiratory samples obtained from patients with unknown pneumonia. 2 As of March 31, 2022, about 485 million confirmed cases have been reported worldwide with more than 6.1 million deaths. 3

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“…Recently, a quantitative and fully automated antigen test based on chemiluminescence enzyme-immunoassay has been launched on the market [5] . This assay, named Lumipulse®G SARS-CoV-2 Ag (LPG) (Fujirebio, Japan), is an accurate diagnostic tool for SARS-CoV-2 [ 6 , 7 , 8 , 9 ]. Nevertheless, using this test, a variable percentage of false-positive results has been reported [ 10 , 11 ], and a grey zone (between 1.34 and 10.0 pg/mL) has been suggested by the Manufacturer.…”

mentioning

confidence: 99%

“…Of the 3070 samples, 411 were immediately analysed using a molecular-fast (MF) assay (i.e., GeneXpert®) as patients were judged to require a time-dependent intervention following triage. The remaining 2659 samples, including 636 from symptomatic and 2023 from asymptomatic patients, were analysed with the LPG antigen test, using the Lumipulse 600II automated system, after centrifugation at 5000 g for 5′ [9] , and were also tested with the SARS-CoV-2 ELITe MGB® RT-PCR assay (ELITechGroup, France). Statistical analyses were carried out using the RT-PCR as the reference test for the diagnosis of SARS-CoV-2 infection (http://vassarstats.net).…”

mentioning

confidence: 99%