Real World Performance of SARS-CoV-2 Antigen Rapid Diagnostic Tests in Various Clinical Settings

Abstract

Objective:

To assess the validity of Antigen rapid diagnostic tests (Ag-RDT) for SARS-CoV-2 as decision support tool in various hospital-based clinical settings.

Design:

Retrospective cohort study among symptomatic and asymptomatic patients and Healthcare workers (HCW).

Setting:

A large tertiary teaching medical center serving as a major COVID-19 hospitalizing facility.

Participants and Methods:

Ag-RDTs’ performance was assessed in three clinical settings: 1. Symptomatic patients and HCW presenting at the Emergency Departments 2. Asymptomatic patients screened upon hospitalization 3. HCW of all sectors tested at the HCW clinic following exposure.

Results:

We obtained 5172 samples from 4595 individuals, who had both Ag-RDT and quantitative real-time PCR (qRT-PCR) results available. Of these, 485 samples were positive by qRT-PCR. The positive percent agreement (PPA) of Ag-RDT was greater for lower cycle threshold (Ct) values, reaching 93% in cases where Ct-value was <25 and 85% where Ct-value was <30. PPA was similar between symptomatic and asymptomatic individuals. We observed a significant correlation between Ct-value and time from infection onset (p<0.001).

Conclusions:

Ag-RDT are highly sensitive to the infectious stage of COVID-19 manifested by either high viral load (lower Ct) or proximity to infection, whether patient is symptomatic or asymptomatic. Thus, this simple-to-use and inexpensive detection method can be used as a decision support tool in various in-hospital clinical settings, assisting patient flow and maintaining sufficient hospital staffing.

SciScore for 10.1101/2021.03.02.21252400: (What is this?)

Please note, not all rigor criteria are appropriate for all manuscripts.

Table 1: Rigor

Institutional Review Board Statement	IRB: Ethical committee approval: The research protocol was approved by the Sheba Institutional Review Board and oral informed consent was obtained from study participants. Consent: Ethical committee approval: The research protocol was approved by the Sheba Institutional Review Board and oral informed consent was obtained from study participants.
Randomization	not detected.
Blinding	not detected.
Power Analysis	not detected.
Sex as a biological variable	Study population and Ag-RDT testing strategies: Three major testing strategies were used in this study: 1) As a decision support tool in the patient triage process, for a cohort of symptomatic patients, mostly visiting ED, who were suspected as being infected with SARS-CoV-2 (Figure 1) 2) As a strategy for early detection of asymptomatic cases among two cohorts: i) asymptomatic patients screened for COVID-19, including women before delivery arriving to the obstetric ED (OB-ED), and ii) a cohort of HCW, who were screened following exposure to a detected COVID-19 case.

Table 2: Resources

Antibodies
Sentences	Resources
Data included socio-demographic details, as well as duration, type of symptoms and laboratory tests including previous or proceeding SARS-CoV-2 qRT-PCR tests and SARS-CoV-2 IgG antibody levels when available.	SARS-CoV-2 IgG suggested: None

Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:

The study had several limitations. First, day of infection onset was defined as either day of first positive qRT-PCR, or day of symptoms onset, yet for some patients this may not be the precise day of infection, and we suspect that many of those diagnosed on day 0, were actually already infected for several days (19). This may particularly be frequent for the asymptomatic patients, whom are likely more frequently recovering and no longer infectious by the time they are detected(17). Second, we did not test a single specific Ag-RDT, but rather combined the results of several kits. This was done, since our objective was to show the potential use of the method, rather than the performance of a specific kit. But since the performance of each kit in similar settings did not differ significantly, we believe that for our objective this is not a significant limitation. In conclusion, this report of a real-life experience with SARS-CoV-2 RDT’s offers several settings in which both its PPV and NPV prove of value. The very high specificity enables immediate rule-in of positive SARS-CoV-2 infectious cases, be it symptomatic ED patients, exposed or early-recovered HCW. Despite the lower analytic sensitivity, accumulating bulk of data support Ag-RDT as a better surrogate for infectivity than PCR, as it represents translated viral proteins rather than RNA remnants. For example, Pekosz et al. (8) shows a better correlation between infectivity and Ag-RDT+/PCR+ cases than Ag-RDT-/PCR+ cases. I...

Results from TrialIdentifier: No clinical trial numbers were referenced.

Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

Results from JetFighter: We did not find any issues relating to colormaps.

Results from rtransparent:

Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
No protocol registration statement was detected.

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