A total of 4,008 and 2,951 patients had the PCR test and the antibody assay, respectively. control Samples were processed AMG 900 only once. In each run, a positive and a negative control were included to allow for correct interpretation of the results. Moreover, the presence of an internal positive control (IPC) in each run ensures the correct performance of the amplification mix. Interpretation of the test results The sample was considered positive for SARS-COV2 when the obtained Ct value was less than 38 and the IPC showed an amplification signal. On the other hand, a negative sample would have no amplification signal, but the IPC would be positive to exclude the inhibition of the PCR reaction. The absence of a signal in the positive control or the presence of amplification in the negative control would denote invalid test results. II-Detection of SARS-COV2 total antibodies The Elecsys? Anti-SARS-CoV-2 is an immunoassay for the invitro qualitative detection of antibodies (including IgG) to SARS-CoV-2 in human serum and plasma. The assay uses a recombinant protein AMG 900 representing the nucleocapsid (N) antigen in a double-antigen sandwich assay format, which favors detection of high affinity antibodies against SARS-CoV-2. The test is intended as an aid in the determination of the immune reaction to SARS-CoV-2. A volume of 20 L of the patient serum was incubated with a mix of biotinylated and ruthenylated nucleocapsid AMG 900 (N) antigen. Double-antigen sandwich immune complexes are formed in the presence of corresponding antibodies. After the addition of streptavidin-coated microparticles, the double-antigen complexes bind to the solid phase via the interaction of biotin and streptavidin. The reagent mixture is transferred to the measuring cell, where the microparticles are magnetically captured on the surface of the electrode. Unbound substances are subsequently removed. Electrochemiluminescence is then induced by applying a voltage and is measured using a photomultiplier. The signal yield increases with the antibody titer. A cutoff index of 1.0 is considered non-reactive, whereas a cutoff index of 1 1.0 is considered reactive. Statistical analysis Data were validated, cleaned, and entered into a spreadsheet. Qualitative data were presented in frequency and related percentages. The level of antibodies was presented by median and interquartile range with the MannCWhitney U test used for comparison. Unadjusted frequency of positive screening among the total was calculated with a 95% confidence interval. Given that SARS-CoV-2 PCR sensitivity was reported to be between 71%C95% , the PCR positivity was adjusted for test sensitivity for both scenarios with a specificity of 99.9%. The antibody seroprevalence was adjusted for kit sensitivity and specificity. According to the manufacturers package insert, Elecsys?.Anti-SARS-CoV-2 exhibits a high overall clinical specificity of 99.81% with no cross-reactivity to the common cold coronaviruses and a sensitivity of 100%. We used the ClopperCPearson exact method to calculate 95% confidence intervals. Comparison between groups was done using a Chi-square test with a P value of 0.05 as the level of significance. The odds ratio was calculated for the estimation of risk with a 95% confidence interval. Logistic regression was used for adjustment of the confounding factors. SPSS program version 15 was used for the analysis. Epitools Epidemiological Calculators. Ausvet. was used for adjustment for tests sensitivity and specificity. Available at: http://epitools.ausvet.com.au Results The current research enrolled 4,313 subjects during the study period. A total of 4,008 and 2,951 patients had the PCR test and the antibody assay, respectively. Females constituted 56% of the study sample. Adults and middle-aged individuals represented around 60% of the sample. Most patients (91.3%) did not complain about any related COVID-19 symptoms (Table 1). Table 1 Characteristics of the study group. thead th align=”justify” rowspan=”1″ colspan=”1″ /th th align=”justify” rowspan=”1″ colspan=”1″ No. (%) /th /thead Total no4313Age (years)???? 18928 (21.5)????18C1356 (31.4)????40C1214 (28.1)????60815 (18.9)Gender????Male1885 (43.7)????Females2428 (56.3)Hospital????1. Obstetrics and gynecology703 (16.3)????2. Oncology49 (1.1)????3. Surgery1463 (33.9)????4. Pediatrics443 (10.3)????5. Internal medicine1421 (32.9)????6. Cardiothoracic234 (5.4)Symptoms????1. No COVID-19 related symptoms3939 (91.3)????2. Fever262 (6.1)????3. Cough165 (3.8)????4. Diarrhea85 (2.0)????5. Sore throat106 (2.5)????6. Vascular event44 (1.0)Morbidities????1. (N = 3659)298 (8.1)????2. HTN (N = 3659)352 (9.6)No. of PCR done4008 (92.9)No. of AB assay done2951 (68.4) Open in a separate window The unadjusted positivity rate of SARS-CoV-2 PCR during the study period was 154 (3.84%; 95% CI 3.29C4.48), while that of SARS-CoV-2 antibodies in the negative PCR group was 877 (29.96%; 95% CI 28.33%C31.65%) during the same period. With adjustment for test sensitivity and specificity, the positive PCR rate ranged from 3.94% in the high sensitivity scenario (95% CI: 3.34C4.62) to 5.28% (95% CI: AMG 900 4.47C6.18) in the low sensitivity scenario. The adjusted SARS-CoV-2 antibody seroprevalence was 29.82 (95% CI: 28.16C31.51) (Table 2). Table 2 Results of SARS-CoV-2 screening by PCR and total antibody. thead th align=”justify” rowspan=”1″ colspan=”1″ /th th align=”justify” rowspan=”1″ colspan=”1″ No. (unadjusted %, 95% CI) Tmem1 /th th align=”justify” rowspan=”1″ colspan=”1″ Adjusted * % (95% CI) /th /thead Positive PCR in total group (N.