Self-swabbing versus assisted swabbing for viral detection by qRT-PCR: the experience from SARS-CoV-2 based on a meta-analysis of six prospectively designed evaluations conducted in a UK setting.

PURPOSE: In April 2020, the UK Government implemented NHS Test and Trace to provide SARS-CoV-2 quantitative reverse transcription polymerase chain reaction (qRT-PCR) testing for the public, with nose-and-throat swabbing for samples performed by trained staff. Self-swabbing (SS) would allow rapid scale-up of testing capacity and access. Six studies were undertaken to determine whether SS was as effective for detecting SARS-CoV-2 as swabbing performed by trained staff. METHODS: Six prospective studies were conducted between April-October 2020, using six swab/media combinations. Differences between assisted swabbing (AS) and SS were evaluated for concordance, positivity, sensitivity, cycle threshold (Ct) values and void rates. Statistical analysis was performed using 95% confidence intervals (CIs), paired t-tests and model-based methods. RESULTS: Overall, 3,253 individuals were recruited (median age 37 years, 49% female), with 2,933 having valid paired qRT-PCR results. Pooled concordance rate was 98% (95% CI: 96%, 99%). Positivity rate differences for SS (8.1%) and AS (8.4%) and differences in pooled sensitivities between SS (86%; 95% CI: 78%, 92%) and AS (91%; 95% CI: 78%, 96%) were nonsignificant. Both types of swabbing led to pooled void rates below 2% and strongly correlated Ct values. Age, sex and previous swabbing experience did not have a significant impact on concordance or sensitivity. CONCLUSION: The UK adopted a policy to promote self-testing for SARS-CoV-2 based on data demonstrating equivalence of SS versus AS. Positive outcomes with SS are likely generalisable to testing for other respiratory pathogens, and we consider self-sampling and self-testing essential for future pandemic preparedness.

The evaluation of a multi-day testing approach with antigen lateral flow devices for people eligible for community-based COVID-19 treatments.

BACKGROUND: COVID-19 therapeutics including antiviral and monoclonal antibody treatments (hereafter 'COVID-19 treatments') require rapid administration to be effective. As part of the community-based antiviral and therapeutic treatment pathway for COVID-19 there has been a move from PCR testing in those eligible to a rapid antigen lateral flow testing regime. OBJECTIVES: To determine whether a multi-day lateral flow device (LFD) testing regime is a feasible alternative to PCR for diagnosing symptomatic patients eligible for COVID-19 treatments. An LFD regime might return a positive result more quickly than a PCR and hence expedite access to COVID-19 treatments. METHODS: A retrospective analysis was conducted of diagnostic testing for SARS-CoV-2 with a combination of PCR and LFDs of symptomatic patients eligible for COVID-19 treatments. LFD testing patterns were not assigned. Patients self-censored and the patterns were retro-fitted to the observed results. RESULTS: The LFD testing patterns offered high sensitivity, close to 92%; however, the false positive rate also increased, with most of the multi-day testing patterns having a false positive rate greater than 3%. The highest sensitivity was seen among patients who tested with LFD on the same day as PCR. CONCLUSIONS: There were multiple observed testing behaviours. We conclude that multi-day LFD testing for COVID-19 provides a feasible alternative to PCR to in eligible patients, allowing swift prescription of COVID-19 treatments in most cases. This approach requires acceptance of a trade-off for a small increase in false-positive and -negative results.

PCR testing of traced contacts for SARS-CoV-2 in England, January to July 2021.

BackgroundThe NHS Test and Trace (NHSTT) programme was established in May 2020 in England to deliver SARS-CoV-2 testing and contact tracing in order to identify infected individuals and reduce COVID-19 spread. To further control transmission, people identified as contacts were asked to self-isolate for 10 days and test only if they became symptomatic. From March 2021, eligibility criteria for PCR testing expanded to include asymptomatic contacts of confirmed cases.AimTo analyse testing patterns of contacts before and after the change in testing guidance in England to assess the impact on PCR testing behaviour with respect to symptom status and contact type.MethodsTesting and contact tracing data were extracted from the national data systems and linked. Subsequently, descriptive statistical analysis was applied to identify trends in testing behaviour.ResultsBetween 1 January and 31 July 2021, over 5 million contacts were identified and reached by contact tracers; 42.3% took a PCR test around the time they were traced. Overall positivity rate was 44.3% and consistently higher in symptomatic (60-70%) than asymptomatic (around 20%, March-June) contacts. The proportion of tests taken by asymptomatic contacts increased over time, especially after the change in testing guidance. No link was observed between uptake of PCR tests and vaccination coverage. Fully vaccinated contacts showed lower positivity (23.8%) than those with one dose (37.2%) or unvaccinated (51.0%).ConclusionAlmost 1 million asymptomatic contacts were tested for SARS-CoV-2, identifying 214,056 positive cases, demonstrating the value of offering PCR testing to this group.

Double testing with lateral flow antigen test devices for COVID-19: does a second test in quick succession add value?

BACKGROUND/OBJECTIVES: We investigated if performing two lateral flow device (LFD) tests, LFD2 immediately after LFD1, could improve diagnostic sensitivity or specificity for detecting severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) antigen. STUDY DESIGN: Individuals aged ≥16 years attending UK community testing sites (February-May 2021) performed two successive LFD tests and provided a nose-and-throat sample for a polymerase chain reaction (PCR) test. Using the PCR result as the reference diagnosis, we assessed whether improvements could be achieved in sensitivity (by counting a positive result in either LFD as a positive overall test result) or specificity (by using LFD2 as confirmatory test). RESULTS: Overall, 2231 participants were included with 159 (7 %) having a positive PCR test. Of 2223 participants who completed both LFD tests, LFD results were highly concordant both with each other and with PCR tests (>97 %). The proportion of discord LFD results decreased significantly over the study period. Combined LFD usage achieved a sensitivity of 68.6 %, versus 67.1 % for either LFD individually. The specificity increased from 99.5 % to 99.8 % when using LFD2 as confirmatory test. Observed increases in sensitivity and specificity were not statistically significant. Void results were recorded for 31 (1.4 %) LFD1s, 19 (0.9 %) LFD2s and 6 (0.3 %) combined LFD tests. CONCLUSIONS: LFD tests were highly reproducible even when they were performed by untrained users following only written instructions and without supervision. While performing two LFD tests of the same type in quick succession marginally increased sensitivity or specificity, statistically significant improvements were not detected in our study.