This study recorded a total of 90 samples divided into three groups, 30 confirmed patients with Coronavirus (COVID-19) for the first group. They were admitted to Al-Hussein Teaching Hospital in Dhi Qar Governorate, affiliated with the Iraqi Ministry of Health, for the period between October 27 and November 26, 2021. 30 patients had passed the acute infection period and their blood samples were collected during routine clinical trials. Tests. All recorded cases of SARS-CoV-2 infection were confirmed using standard RT-qPCR testing on throat swab samples from the respiratory tract. For all enrolled patients, date of onset of disease, clinical classification of severity, RNA test results during the hospitalization period, and Personal demographic information was obtained from clinical records The highly purified receptor binding domain (RBD) of SARS CoV-2 protein was expressed to detect the presence of IgM, IgG, and C-reactive protein, respectively Using a fluorescence-based POCT immunoassay analyzer (Ichroma™ II). The current study showed that there was a significant increase in the level of IgG antibodies in the group of patients who had passed the acute stage of the Coronavirus (COVID-19), which recorded a significant increase in the levels of IgM antibodies in the serum of patients who were still suffering from severe symptoms of Covid-19 infection. 19 The current study also showed a significant increase in the level of C-reactive protein in the group of patients who were still in the acute stage of infection compared to patients who had passed the stage of acute symptoms of infection. Laboratory tests were conducted to find out the effect of infection with the Coronavirus on some criteria and to know the correlation between some criteria in patients, by evaluating the diagnostic ability and adopting immunological tests as a biological marker for COVID-19 patients