CHALLENGES OF LABORATORY SAMPLING AND DIAGNOSIS OF SARS-COV-2 VIRUS OF DISEASE (COVID-19)

Background & Aims: Given the prevalence of SARS-CoV-2 worldwide, it is essential to identify people infected with the virus and determine its different types to control the global outbreak of COVID-19. The results of the studies are controversial, so this study examines these diagnostic challenges, including the types of diagnostic methods, the type and time of sampling, and even the clinical condition of the disease. Materials & Methods: In this systematic review, studies conducted from 2003 to May 2020 in English on the challenges of laboratory sampling and diagnostics of coronaviruses and SARS-CoV-2 virus were reviewed. These articles were obtained by searching for keywords in databases, PubMed, Scopus and Embace as well as Google scholar search engine and duplicate articles were removed from the study. Results: In the initial search, 98 articles were extracted that after eliminating duplicates and evaluating the title and abstract, finally 64 articles had the necessary conditions for review and were included in the study. The results of the studies showed that, although RT-PCR is the gold standard for the diagnosis of Covid-19 disease, but it requires a sufficient concentration of viral RNA in the patient sample for proper evaluation of the sample. Since the concentration of viral RNA in the patient sample is not constant, this can affect the results obtained. Although the best sample to detect the virus in the first days is the nasopharyngeal swab and in the following days, samples taken from the lower respiratory tract, but also numerous samples such as throat swabs and feces can also be used for identification. However, the percentage of viral RNA isolation in these samples is significantly reduced. Conclusion: Due to the global prevalence of Covid-19 disease, early diagnosis of patients, quarantine and timely treatment are of great importance in controlling the epidemic. The use of correct diagnostic tests allows physicians to perform immediate interventions for patients. Although molecular diagnosis is the best method, studies show that it is better not to be satisfied with the results of an experiment and to use a combination of different methods and tests to solve diagnostic challenges.