Clinical and laboratory evaluation of SARS-CoV-2 lateral flow assays for use in a national COVID-19 seroprevalence survey

Abstract

BackgroundAccurate antibody tests are essential to monitor the SARS-CoV-2 pandemic. Lateral flow immunoassays (LFIAs) can deliver testing at scale. However, reported performance varies, and sensitivity analyses have generally been conducted on serum from hospitalised patients. For use in community testing, evaluation of finger-prick self-tests, in non-hospitalised individuals, is required.MethodsSensitivity analysis was conducted on 276 non-hospitalised participants. All had tested positive for SARS-CoV-2 by reverse transcription PCR and were ≥21 days from symptom onset. In phase I, we evaluated five LFIAs in clinic (with finger prick) and laboratory (with blood and sera) in comparison to (1) PCR-confirmed infection and (2) presence of SARS-CoV-2 antibodies on two ‘in-house’ ELISAs. Specificity analysis was performed on 500 prepandemic sera. In phase II, six additional LFIAs were assessed with serum.Findings95% (95% CI 92.2% to 97.3%) of the infected cohort had detectable antibodies on at least one ELISA. LFIA sensitivity was variable, but significantly inferior to ELISA in 8 out of 11 assessed. Of LFIAs assessed in both clinic and laboratory, finger-prick self-test sensitivity varied from 21% to 92% versus PCR-confirmed cases and from 22% to 96% versus composite ELISA positives. Concordance between finger-prick and serum testing was at best moderate (kappa 0.56) and, at worst, slight (kappa 0.13). All LFIAs had high specificity (97.2%–99.8%).InterpretationLFIA sensitivity and sample concordance is variable, highlighting the importance of evaluations in setting of intended use. This rigorous approach to LFIA evaluation identified a test with high specificity (98.6% (95%CI 97.1% to 99.4%)), moderate sensitivity (84.4% with finger prick (95% CI 70.5% to 93.5%)) and moderate concordance, suitable for seroprevalence surveys.

Antibody response to SARS-CoV-2 infection in humans: a systematic review

“…130 However, in the UK, nationally validated assays have been evaluated with convalescent samples from community participants and a number of large-scale serosurveys now use these. [131][132][133] Clear understanding of the kinetics of the response, particularly for the specific N and S antigens, is important for the interpretation of seroprevalence studies.…”

Accuracy of UK Rapid Test Consortium (UK-RTC) “AbC-19 Rapid Test” for detection of previous SARS-CoV-2 infection in key workers: test accuracy study

“…As people who have had SARS-CoV-2 previously confirmed by PCR would probably be less likely to seek antibody testing than other people, we consider this lower estimate (84.7%) to be a more appropriate estimate of test sensitivity for a potential use case in which people were to choose to take the test to find out their own previous infection status. For an alternative potential use of population serosurveillance,34 the estimate of test sensitivity of 86.6% (83.2% to 89.4%), which derives from an analysis of all EDSAB-HOME stream A and B participants, irrespective of PCR positivity, may be more appropriate. Finally, we observed that AbC-19 test bands were often weak, a finding also reported in another laboratory based evaluation of AbC-19 16.…”

“…Most previous evaluations of LFIAs have used a “two gate” design, in which tests are performed on two groups of samples: PCR positives and pre-pandemic sera 24202122. This study design remains an important tool in evaluating accuracy, owing to the lack of a gold standard test, as discussed above.…”

“…Several lateral flow immunoassays (LFIAs)—small, pregnancy test format devices that can deliver testing rapidly and at scale—have recently become available that detect antibodies against SARS-CoV-2 proteins. These devices have two potential main uses: population serosurveillance and assessment of individual risk of developing immunity to coronavirus disease 2019 (covid-19) 345. The US Food and Drug Administration recently (24 September 2020) licensed an LFIA for office use (that is, in supervised environments), on the basis that it may predict immunity (https://www.fda.gov/media/139789/download); if this is validated, then it could result in widespread use of this class of devices.…”

Self-sampling of capillary blood for serological testing of SARS-CoV-2 by COVID-19 IgG ELISA

“…The copyright holder for this this version posted September 27, 2020. ; https://doi.org/10.1101/2020.09.25.20183459 doi: medRxiv preprint sensitivity (21% to 92%), that was significantly inferior to ELISAs performed on venous blood (Flower et al, 2020). Studies have shown high sensitivity of ELISAs for the detection of SARS-CoV-2 antibodies in venous blood (Adams et al, 2020;Lisboa Bastos et al, 2020;Staines et al, 2020).…”