Introduction
Infection with Coronavirus (CoV) diseases (COVID-19), which is caused by
novel sever acute respiratory syndrome CoV-2 (SARS-CoV-2), was firstly
reported in Wuhan, China in December 2019
(Akashi et al., 2019). On 11 March 2020,
the World Health Organization (WHO) declared COVID-19 as a pandemic of
global concern (WHO, 11 March 2020.).
After one year from the initial China outbreak, there have been
tremendous increase in the number of confirmed cases as well as death
records worldwide. As of 21 January 2021, ~ 95 million
COVID-19 cases were confirmed worldwide and more than two million deaths
were reported (WHO, 11 January 2020.).
Egypt was among the first 10 countries in Africa that experienced
COVID-19 cases (Nkengasong & Mankoula,
2020). By 3 January 2021, Egypt has reported 144.583 confirmed cases
with 5.4% of them (7.918) died of the pandemic
(WHO, 11 January 2020.). The sudden and
unprecedented surge in the number of reported cases is overwhelming the
capacity of the national healthcare system, particularly in the
developing countries (Leung et al.,
2020). Central to the containment of the ongoing pandemic is the
availability of rapid and accurate diagnostic tests that could pinpoint
patients at early disease stages before further spread occur.
Reverse transcriptase quantitative real-time PCR (RT-qPCR) assay has
been the gold standard for diagnosing COVID-19 in many health sectors
and laboratories (Shen et al., 2020;
Tang, Schmitz, Persing, & Stratton,
2020; van Kasteren et al., 2020).
However, this assay often done in large centralized hospitals or
laboratories away from the access of local inhabitants, it requires long
time-to-results, skilled staff and specialized instruments and is of
high cost. This is particularly the case in many developing countries,
including Egypt (Anjum, Anam, & Rahman,
2020). In Egypt, the RT-qPCR diagnosis is mostly done in Cairo, the
capital or in capitals of governorates leading to an overall
turn-around-time of ~ 24 hours at best between shipping
the samples and obtaining the results
(Sheridan, 2020). Indeed, suspected
individuals often go first to the local clinics for emergency where
RT-qPCR might not be available. The RT-qPCR may not be able to cope with
the testing or screening needs in the low and middle-income countries
due to limited infrastructure, low fund and limited human resources
(Olalekan et al., 2020). To fill in this
gap and to improve this situation, rapid antigen tests (RATs) are being
developed and are in use as point-of-care diagnostic tools in local
settings and emergency departments (Wee et
al., 2020). They offer the advantage of being quick and can be done
simply without need for special equipment
(Lambert-Niclot et al., 2020;
Nalumansi et al., 2020;
Scohy et al., 2020). Determining the
diagnostic performance of commercialized RAT is crucial because this
gives indication about their reliability and clinical utility during the
time of pandemic.
There have been many RAT available for diagnosis of COVID-19 (reviewed
in (Olalekan et al., 2020)), yet their
clinical applicability is questionable because their accuracy is low as
compared to RT-qPCR, their diagnostic performance is highly variable,
even when the same assay was applied in two different population with
different ethnicity background (Chaimayo et
al., 2020; Nalumansi et al., 2020) and
their accuracy is host- and virus-dependent
(Chaimayo et al., 2020;
Tang et al., 2020). Similar to other
countries, several RATs have been under development in Egypt, but the
available studies lack detailed characterization of RAT performance,
especially the impact of patients criteria, clinical features, sampling
time and viral load on the test performance. Actually, only one RAT
(BIOCREDIT COVID-19 antigen test) has been recently evaluated in Egypt
(A. M. Abdelrazik, S. M. Elshafie, & H. M.
Abdelaziz, 2020). In the current study, we aimed to add to the current
knowledge by evaluating the clinical utility of a recently
commercialized RAT, Standard ™ Q COVID-19 Ag, in a number of Egyptian
participants, who are suspected of having COVID-19. We also studied the
influence of various factors on the assay performance and tested the
hypothesis that measuring laboratory parameters could enhance RAT
predictive accuracy when RT-qPCR is not available.