Field performance of NowCheck rapid antigen test for SARS-CoV-2 in Kisumu County, western Kenya

Abstract

Background Low- and middle-income countries (LMICs) are increasingly adopting low-cost Coronavirus disease 2019 (COVID-19) rapid antigen tests to meet the high demand for SARS-CoV-2 testing. Whilst testing using real-time polymerase chain reaction (RT-PCR) is the current gold standard, its widespread use in LMICs is limited by high costs, turnaround times and is not readily available in most places. COVID-19 antigen tests (Ag-RDT) provide a suitable alternative due to their low cost, rapid turnaround time and easy to set up and use. This study aimed to assess the field performance of the NowCheck COVID-19 antigen kit (Ag-RDT) as a point of care test (POCT) in select healthcare facilities in western Kenya. Methods We conducted a prospective multi-facility field evaluation study of the NowCheck COVID-19 rapid antigen test (Ag-RDT) compared to SARS-CoV-2 RT-PCR (RT-PCR). After obtaining informed consent, trained laboratory technicians collected two pairs of oropharyngeal and nasopharyngeal swabs, both antigen and RT-PCR testing, first for Ag-RDT and next for RT-PCR. We performed Ag-RDTs on-site and shared the results with both the study participants and their healthcare providers within 15-30 minutes. We carried out all RT-PCR tests in a central referral laboratory. The turnaround time for RT-PCR results was typically 24-48 hours. We captured the results of both methods using an electronic digital application. Findings Between December 2020 and March 2021, we enrolled 997 participants who met the Kenyan Ministry of Health COVID-19 case definition. The median age of study participants was 39 years (range one to 80 years), with 54% male. Ag-RDT had a sensitivity of 84.5% (76.0-90.8) and a specificity of 94.4% (95% CI: 92.7-95.8) with an accuracy of 94.2% (92.5- 95.6) when a cycle threshold value (Ct value) of ≤35 was used. The highest sensitivity of 87.7% (77.2-94.5) was observed in samples with Ct values ≤ 30 and the highest specificity of 97.5% (96.2-98.5) at Ct value of <40. Interpretation The NowCheck COVID-19 Ag-RDT showed good performance in field evaluation in multiple healthcare facilities in a developing country. The sensitivity of the kit exceeded the minimum recommended cut-off of 80% as recommended by WHO1. The high specificity of this kit at 94.4% at Ct values ≤33 and 97.5% at Ct values <40 matched that of real-time PCR, making it a good rule-out test for symptomatic patients with COVID-19- like symptoms. The faster turnaround time to results, lower cost, simple analytical steps requiring no equipment or infrastructure makes antigen testing an attractive field-screening method to meet the high demand for COVID-19 testing.

Accuracy of rapid point-of-care antigen-based diagnostics for SARS-CoV-2: an updated systematic review and meta-analysis with meta regression analyzing influencing factors

“…At the end of the data extraction process, 21 studies were still in preprint form [16, 17, 21, 47, 50, 55, 58, 65, 69, 74, 84, 100, 116, 121, 129, 160, 167, 168, 173, 174, 186]. All studies were written in English, except for 3 in Spanish [53, 62, 134], 1 in Turkish [95], and 1 in French [153].…”

“…Further 20 studies were included from the FIND website [190][191][192][193][194][195][196][197][198][199][200][201][202][203][204][205][206][207][208][209] (Fig 1). At the end of the data extraction process, 21 studies were still in preprint form [16,17,21,47,50,55,58,65,69,74,84,100,116,121,129,160,167,168,173,174,186]. All studies were written in English, except for 3 in Spanish [53,62,134], 1 in Turkish [95], and 1 in French [153].…”

Health workers’ Perspective on the Feasibility and Acceptability of the Introduction of AgRDT for COVID-19 in Kisumu County, Western Kenya

“…The RDT tested in our PPP project was of internationally recognized quality, could be ordered easily at lower quantities-suitable for individual hospitals, at low price (<$3/test) and shipped from South Korea to Nairobi within a week. Therefore, this test was chosen to be field-evaluated, which actually was accomplished (8). Currently the process has been started to license this AgRDT for use in Kenya.…”

Linking private health sector to public COVID-19 response in Kisumu, Kenya: Lessons Learnt

“…First of all, this PPP, despite all its efforts, led to the experience of general lack of SARS-CoV-2 testing capacity through PCR. Therefore, an intervention was established introducing for the very first time rapid diagnostic COVID-19 tests and validating their performance in Kisumu field-setting (13). This has opened the possibility for private facilities to complementarily procure rapid tests in relatively smaller quantities at affordable prices and thus be less dependent of government supplies and in general increase the COVID-19 testing capacity for Kisumu citizens.…”

“…First of all, this PPP, despite all its efforts, led to the experience of general lack of SARS-CoV-2 testing capacity through PCR. Therefore, an intervention was established introducing for the very first time rapid diagnostic COVID-19 tests and validating their performance in Kisumu field-setting (13).…”