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Background & Objective: The prevalence of COVID-19 and its severity have been observed to be on a lower level in underdeveloped countries with poorer standards of hygiene. This disparity may be attributed to the higher seroprevalence of other viral diseases, which can result in the presence of antibodies protective against COVID-19. Two of the widespread diseases in such countries are infection to hepatitis A and E viruses (HAV and HEV). In the present study, we explored the relationship between the level of antibodies against these viruses and the susceptibility to COVID-19. Methods: Ninety patients were studied in two groups of controls and cases, each consisting 45 individuals. The cases were patients with the clinical symptoms of COVID-19 and positive RT-PCR test results. The controls were individuals referred to the respiratory triage of Imam Khomeini Hospital Complex and were not demonstrating relevant clinical symptoms of COVID-19 and their RT-PCR test results were negative. Levels of HAV and HEV antibodies were measured and compared in these two groups. Results: The median of HAV antibody level was 13.6 (IQR=11.5-16.9) and 13.2 (IQR =10.7-14.7) in cases and controls, respectively, showing no statistically significant difference (P=0.1). Likewise, the median of HEV antibody level was 6.7 (IQR=5.3-7.1) and 7.1 (IQR=6.3-7.5) in cases and controls, respectively, which again showed no statistically significant difference (P=0.41). Conclusion: The present study was carried out in a region with a relatively high prevalence of HAV and HEV infections. Contrary to our expectations, no statistically significant relationship was observed between the levels of antibodies against these viruses and the susceptibility to COVID-19. Further studies with larger sample sizes and in other countries are needed to come to a definite conclusion. [ABSTRACT FROM AUTHOR]

Background & Objective: COVID-19 reverse transcription-polymerase chain reaction (RT-PCR) has been a reference test for diagnosing a disease since the very beginning of the pandemic. COVID-19 serology tests have also been developed and used to estimate the prevalence of individuals who have already been infected. We aimed to evaluate the performance of serology tests for the diagnosis of patients who had been referred to medical centers with acute symptoms. Methods: In this cross-sectional study, 80 individuals suspected of COVID-19 who had been referred to Imam Khomeini Hospital Complex, Tehran, Iran, were examined. Upper respiratory tract specimens for RT-PCR and blood samples for COVID-19 IgM and IgG antibody level tests were collected and the results were compared. Results: The overall proportion in agreement, the agreement between positive results, and the agreement between negative results when comparing RT-PCR and IgM serology test were 40% (kappa = -0.006, P = 0.9), 32%, and 66.6%, respectively, and when comparing RT-PCR and IgG serology test were 46% (kappa = -0.006, P = 0.94), 43.5%, and 55.5%, respectively. Conclusion: The absence of a gold standard method for the diagnosis of COVID-19 makes it very challenging to determine the true sensitivity and specificity of different methods. The study results revealed no agreement between the two methods; so the RT-PCR test for upper respiratory tract specimen cannot be replaced with COVID-19 serology test for the diagnosis of patients with acute symptoms. [ABSTRACT FROM AUTHOR]