**5. Medical laboratory methods, techniques and technologies applied for COVID-19 testing**

The medical laboratory methods and technologies applied in testing COVID-19 includes: neutralization/virological cell culture test, COVID-19 genomic sequencing, nucleic acid testing (NAT) /amplification testing, polymerase chain reaction (PCR), real time PCR (RT- PCR) and Gene Xpert systems, immunological testing, biosensors, rapid diagnostic techniques (RDTs) [15]. These methods are illustrated in **Figure 1**.

Basically, virological cell culture test is the gold standard for virus discovery, pathogenesis research and strategy evaluation but since the emergence of COVID-19, PCR has been adopted as the gold standard and has been in use globally considering the shorter turnaround time. Genomic sequencing uses sophistication to track the

#### **Figure 1.**

*Diagnostic methods and technologies employed in COVID-19 testing. KEY: CBPB, cell-based potentiometric biose; CLIA, Chemiluminescence immunoassay; ddPCR, droplet digital PCR; E-gene, envelope protein gene; ELISA, enzyme-linked immunosorbent assay; FET, field effect transistor; IFA, Immunoflorescence assay; LAMP, loop mediated isothermal amplification; LFIA, lateral flow immunoassay; LSPR, localized surface plasmon resonance (sensor); MCLIA, magnetic Chemiluminescence enzyme immunoassay; M, membrane protein gene; N-gene, Nucleocapsid protein gene; NAT, nucleic acid testing; PCR, polymerase chain reaction; ORF, open reading frame; OSN-qRT, PCR - one step nested RT-PCR; qRT-PCR, real-time quantification PCR; RDT, rapid diagnostic technique; RdRp, RNA-dependent RNA polymerasegene; S, spike proteins.*

**Figure 2.** *NCDC medical laboratory testing algorithm in Nigeria while using RDTs.*

pandemic and aids vaccine development [16]. Immunological testing is based on the quantification and detection of antigen and antibody interactions. Biosensors use selectivity features of a bimolecular and sensitivity of physiochemical transducers in COVID-19 testing. Rapid Diagnostic Techniques (RDTs) are new technologies which apply some of the above mentioned techniques to achieve shortest turnaround time and accessibility. Although each method has its advantages and disadvantages, it is advisable to employ at least two methods [15, 17–19] for quality medical laboratory testing especially when using RDTs as shown in **Figure 2**.
