Prospects of biotechnological production and adoption of COVID-19 serological assays in Nigeria

¹Department of Medical Laboratory Science, Faculty of Allied Health Sciences, Ahmadu Bello University, Zaria, Nigeria, ²Department of Medical Microbiology and Parasitology, Bayero University, Kano, Nigeria, ³Department of Medical Laboratory Science, Kwara State University, Mellete, Nigeria

^&Corresponding author
Idris Nasir Abdullahi, Department of Medical Laboratory Science, Faculty of Allied Health Sciences, Ahmadu Bello University, Zaria, Nigeria

To the Editors of the Pan African Medical Journal    

For over 8 months of its emergence, the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), the causative agent of the Coronavirus Disease 2019 (COVID-19) pandemic has resulted to unprecedented global health challenge and economic uncertainties. Till date, the World Health Organization (WHO) recommended the Reverse Transcription-Polymerase Chain Reaction (RT-PCR) as the gold standard for COVID-19 diagnosis. As at 30^th August 2020, there were 53727 RT-PCR confirmed COVID-19 cases out of the 398304 tested persons in Nigeria [1]. Even though the government of Nigeria has been activating some laboratories to scale-up its testing capacity, many observers have attributed the relatively low reported COVID-19 cases to underdiagnosis, probably due to inadequate molecular diagnostic capacity and few human resources skilled in molecular diagnostic tests [2]. Although appropriate use of RT-PCR provides very accurate results, test reagents and consumables are mostly in short supply. Besides, this protocol is laborious, expensive to operate and has a long test turnaround time (TAT) [3]. Aside from these, one of the major technical drawbacks in the use of RT-PCR includes significant cases of false-negative results despite patients having clinical features and radiologic findings highly suspicious of SARS-CoV-2 infection [4]. This could have been due to wrong sampling where SARS-CoV-2 might have been present in the lower respiratory tracts rather than upper respiratory samples often collected for laboratory diagnosis. This poses a challenge in the proper evaluation of some SARS-CoV-2 infected persons.

It has been observed that the transmission dynamics of SARS-CoV-2 has made it a herculean task in its control in Nigeria. Particularly, with the recent identification of a mutant (D614G), a highly transmissible form of SARS-CoV-2 in Nigeria. This necessitates the need to "think out of the box" by searching for highly sensitive and specific anti-SARS-CoV-2 protocols with short TAT. Thus, enabling prompt and large-scale testing for COVID-19. Even though none of the antibody-based Point-of-Care-Test (POCT) devices have been approved by the WHO, a number of antigen (Ag)-based serological assays have been approved for use. Antigen-based serological tests directly detect SARS-CoV-2 proteins of replicating virus in respiratory secretions. This assay has been developed as both ELISA, and for POCT. Most Ag-based POCTs for SARS-COV-2 use the sandwich immunodetection protocol that employs a simple-to-use lateral flow assay (LFA) format commonly employed for other common infectious diseases testing [5]. Available performance characteristics for Ag-based POCTs were derived from studies of different designs. So far, Ag-based POCTs on upper respiratory tract samples have shown variable sensitivity when compared to NAATs, ranging from 0-94%. However, their specificities were consistently reported to be high (>97%) [5]. Although there is the need for more evidence on real-world performance and operational issues, Ag-based POCTs will most likely perform well in patients with high viral loads which usually appear in from day 1 to 3 before the onset of symptoms (pre-symptomatic) and during the early symptomatic periods of COVID-19 (usually from 5-7 days of illness). This could offer an opportunity for prompt diagnosis and interruption of transmission through targeted isolation of most infectious cases and their close contacts [5]. Despite these expected limitations in performance, if correctly performed and interpreted, Ag-based COVID-19 POCTs could have a significant application in patient management, surveillance and other public health decision making [5]. Diagnostically, Ag-based POCTs need to have sensitivity ≥80% and have very high specificity of ≥97-100% [5]. Furthermore, several reports have demonstrated the ability of antibody-based POCTs to assist in the sero-epidemiological analyses of the ongoing COVID-19 pandemic. The immuno-kinetics of SARS-CoV-2 infection shows that serum anti-SARS-CoV-2 IgM is detectable by the third day after infection, while anti-SARS-CoV-2 IgG levels rise when anti-SARS-CoV-2 IgM levels begin to decline at day 7 [6]. Essentially, the technical rigor and quality of specimen requirements for these tests are relatively lesser than those of RT-PCR protocols.

So far, two major concerns with serological tests are the possibility of missing acute SARS-CoV-2 infection during "window period" and the possibility to "cross-reaction" with some SARS-CoVs, due to their high nucleotide homology with SARS-CoV-2 [7]. Despite these, the performance characteristics of various serological assays were incredibly encouraging. For instance, the Cellex® qSARS-CoV-2 IgM/IgG POCT devices showed 96.7%, 96%, 92.3% and 96.8% sensitivity, specificity, positive predictive and negative predictive values, respectively [8]. To attain sufficient public health laboratory response required for the adequate containment of the COVID-19 pandemic in Nigeria, the National Biotechnology Development Agency; National In-vitro Diagnostics Control Laboratory; private biotechnology firms and regulatory authorities should consider local production, post-production evaluation and standardization of POCT devices to scale-up Nigeria´s COVID-19 testing capacity viz a viz avoid inaccurate results. By this, many biomedical science-related professionals will be employed. Besides, Nigeria could consider the exportation of quality assured COVID-19 POCT devices to neighboring African countries. This will ameliorate the impact of the COVID-19 pandemic on Nigeria´s health economy.

Competing interests    

The authors declare no competing interests.

Authors' contributions     

Idris Nasir Abdullahi conceptualized and designed the article. Idris Nasir Abdullahi, Kabir Umar and Pius Omoruyi Omosigho did the literature search, drafted the manuscript, and reviewed it for intellectual content. All the authors have read and agreed to the final manuscript.

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