UK study determines PCR confirmation not necessary for confirmation of positive result of Innova Antigen tests.
https://assets.publishing.service.gov.uk/gove...hase-4.pdf
Lateral flow device specificity in phase 4 (post marketing) surveillance
Published 10 March 2021
Authors: Achim Wolf (1), Jack Hulmes (1), Susan Hopkins (2)
(1) NHS Test and Trace, Department of Health & Social Care, London, UK
(2) Public Health England, London, UK
Summary
Public Health England (PHE) and Oxford University evaluated the performance of the Innova LFD device against PCR. In phase 2 and 3a, where the same sample was used for both PCR and LFD specificity analyses, no false positives were detected. We conducted a Phase 4, post marketing surveillance study in 7,546 individuals with a negative PCR result and compared those results with the LFD results from a separate sample. This study identified 21 (0.28%) discordant test pairs and therefore concluded that the specificity of the LFD device was 99.72%. However, this analysis assumed a sensitivity for the PCR of 100% (i.e. that on all 21 discordant samples the PCR, and not the LFD, gave the correct result). Analysis of the Phase 4 data can also be interpreted with lower PCR sensitivity levels and is consistent with a PCR sensitivity ranging from 94.2% to 100% and an associated LFD specificity ranging from 100% to 99.72%.
Subsequently we have analysed data from LFD Community Testing at NHS Test and
Trace Asymptomatic Testing Sites (ATSs) from 20 November 2020 to 27 January 2021; 1,700,972 were conducted and 38,270 (2.2%) LFDs returned a positive result. Among positive LFD results, 25,779 (67%) were matched to a PCR test within the subsequent 5 days. Of those, 24,147 (93.7%) returned a positive PCR result, significantly higher than the 2 positive predictive value expected with LFD specificity of 99.72%. The best statistical fit of this data resulted in LFD specificity of 99.97% and PCR sensitivity of 94.8%. Similar numbers were found in schools (LFD specificity 99.97%, PCR sensitivity 94.4%).
These analyses support the policy of not requiring PCR confirmation of positive LFD tests conducted at ATSs under current levels of population prevalence. The data will be kept under review and further post marketing surveillance analyses conducted at regular intervals
https://assets.publishing.service.gov.uk/gove...hase-4.pdf
Lateral flow device specificity in phase 4 (post marketing) surveillance
Published 10 March 2021
Authors: Achim Wolf (1), Jack Hulmes (1), Susan Hopkins (2)
(1) NHS Test and Trace, Department of Health & Social Care, London, UK
(2) Public Health England, London, UK
Summary
Public Health England (PHE) and Oxford University evaluated the performance of the Innova LFD device against PCR. In phase 2 and 3a, where the same sample was used for both PCR and LFD specificity analyses, no false positives were detected. We conducted a Phase 4, post marketing surveillance study in 7,546 individuals with a negative PCR result and compared those results with the LFD results from a separate sample. This study identified 21 (0.28%) discordant test pairs and therefore concluded that the specificity of the LFD device was 99.72%. However, this analysis assumed a sensitivity for the PCR of 100% (i.e. that on all 21 discordant samples the PCR, and not the LFD, gave the correct result). Analysis of the Phase 4 data can also be interpreted with lower PCR sensitivity levels and is consistent with a PCR sensitivity ranging from 94.2% to 100% and an associated LFD specificity ranging from 100% to 99.72%.
Subsequently we have analysed data from LFD Community Testing at NHS Test and
Trace Asymptomatic Testing Sites (ATSs) from 20 November 2020 to 27 January 2021; 1,700,972 were conducted and 38,270 (2.2%) LFDs returned a positive result. Among positive LFD results, 25,779 (67%) were matched to a PCR test within the subsequent 5 days. Of those, 24,147 (93.7%) returned a positive PCR result, significantly higher than the 2 positive predictive value expected with LFD specificity of 99.72%. The best statistical fit of this data resulted in LFD specificity of 99.97% and PCR sensitivity of 94.8%. Similar numbers were found in schools (LFD specificity 99.97%, PCR sensitivity 94.4%).
These analyses support the policy of not requiring PCR confirmation of positive LFD tests conducted at ATSs under current levels of population prevalence. The data will be kept under review and further post marketing surveillance analyses conducted at regular intervals
