Background The aims of this study are to determine (i) SARS-CoV-2 antibody positive employees in Austrian trauma hospitals and rehabilitation facilities, (ii) number of active virus carriers (symptomatic and asymptomatic) during the study, (iii) antibody decline in seropositive subjects over a period of around 6 months, (iv) the usefulness of rapid antibody tests for outpatient screening. Method A total of 3301 employees in 11 Austrian trauma hospitals and rehabilitation facilities of the Austrian Social Insurance for Occupational Risks (AUVA) participated in this open uncontrolled prospective cohort study. Rapid lateral flow tests, detecting a combination of IgM and IgM against SARS-CoV-2), two different types of CLIA (Diasorin, Roche), RT-PCR tests and serum neutralization tests (SNTs) were performed. The tests were conducted twice, with an interval of 42.4 ± 7.7 (Min = 30, Max = 64) days. Positive participants were re-tested with CLIA/SNT at a third time point after 188.0 ± 12.8 days. Results Only 27 out of 3301 participants (0.82%) had a positive antibody test at any time point during the study confirmed via neutralization test. Among positively tested participants in either test, 50.4% did not report any symptoms consistent with common manifestations of COVID-19 during the study period or within the preceding 6 weeks. In the group who tested positive during or prior to study inclusion the most common symptoms of an acute viral illness were rhinitis (21.9%), and loss of taste and olfactory sense (21.9%). Based on the neutralization test as the true condition, the rapid antibody test performed better on serum than whole blood as 84.6% instead of 65.4% could be detected correctly. Concerning both CLIA tests overall the Roche test detected 24 (sensitivity = 88.9%) and the Diasorin test 22 positive participants (sensitivity = 81.5%). In participants with a positive SNT result, a significant drop in neutralizing antibody titre from 31.8 ± 22.9 (Md = 32.0) at T1 to 26.1 ± 17.6 (Md = 21.3) at T2 to 21.4 ± 13.4 (Md = 16.0) at T3 (χ 2 = 23.848, df = 2, p < 0.001) was observed (χ 2 = 23.848, df = 2, p < 0.001)—with an average time of 42.4 ± 7.7 days between T1 and T2 and 146.9 ± 13.8 days between T2 and T3. Conclusions During the study period (May 11th–August 3rd) only 0.82% were tested positive for antibodies in our study cohort. The antibody concentration decreases significantly over time with 14.8% (4 out of 27) losing detectable antibodies.
【저자키워드】 severe acute respiratory syndrome coronavirus 2, SARS-CoV-2, COVID-19 diagnostic testing, 【초록키워드】 COVID-19, neutralizing antibody, antibodies, CLIA, rapid antibody test, IgM, antibody, neutralization, hospital, rehabilitation, Symptom, prospective cohort study, serum, Viral, SARS-CoV-2 antibody, Asymptomatic, Whole blood, antibody tests, neutralization test, Rapid, Antibody test, Roche, trauma, Combination, RT-PCR test, Concentration, occupational, manifestation, Lateral flow tests, open, Rapid antibody tests, virus carriers, serum neutralization test, insurance, RT-PCR tests, olfactory sense, Social Insurance, DiaSorin, study period, average, loss of taste, participant, study inclusion, titre, study cohort, positive, aims, rehabilitation facility, rhinitis, seropositive subjects, decrease, Result, tested, performed, significantly, detectable, conducted, determine, participated, seropositive subject, symptomatic and asymptomatic, virus carrier, 【제목키워드】 hospital, asymptomatic infection,