Correlation of ELISA based with random access serologic immunoassays for identifying adaptive immune response to SARS-CoV-2 (preprint)

Public health emergency of SARS-CoV-2 has facilitated diagnostic testing as a related medical countermeasure against COVID-19 outbreak. Numerous serologic antibody tests have become available through an expedited federal emergency use only process. This paper highlights the analytical characteristic of an ELISA based assay by AnshLabs and three random access immunoassay (RAIA) by DiaSorin, Roche, and Abbott that have been approved for emergency use authorization (EUA), at a tertiary academic center in a low disease-prevalence area. The AnshLabs gave higher estimates of sero-prevalence, over the three RAIA methods. For positive results, AnshLabs had 93.3% and 100% concordance with DiaSorin or Abbott and Roche respectively. For negative results, AnshLabs had 69.7% and 73.0% concordance with DiaSorin and Roche or Abbott respectively. All discrepant samples that were positive by AnshLabs and negative by RAIA tested positive by all-in-one step SARS-CoV-2 Total (COV2T) assay performed on the automated Siemens Advia Centaur XPT analyzer. None of these methods, however, are useful in early diagnosis of SARSCoV- 2.

Role of Anti-SARS-CoV-2 antibodies in different cohorts: Can they provide clues for appropriate patient triaging? (preprint)

The emergence of coronavirus disease 2019 (COVID-19) has become a major global health crisis. Currently, diagnosis is based on molecular techniques, which detect the viral nucleic acids when present at detectable levels. The serum IgG response against SARS-CoV-2 was examined by using an ELISA-based assay. Serum samples, along with nasopharyngeal specimens were collected from various cohorts and analyzed by ELISA and rRT-PCR, respectively. A total of 167 serum samples were tested for serum IgG antibodies against SARS-CoV-2 in outpatient cohorts, 15 (8.9%) were positive by rRT-PCR and the remaining 152 (91%) were negative. We used these data to generate two different assay cutoffs for serum IgG assay and investigated percent concordance with rRT-PCR test results. The emergency department data revealed, out of 151 nasopharyngeal swabs, 4 (2.6%) were positive by rRT-PCR and 18 (11.9%) were positive for serum IgG assay. Among the 18 patients that were positive for serum IgG, 13 (72.2%) exhibited 1-3 symptoms of COVID-19 and 5 (27.7%) patients did not present with any COVID-19 related symptoms, per CDC criteria. All 4 (100%) patients that were positive by rRT-PCR had symptoms of COVID-19 disease. A longitudinal study from the inpatient population suggested there was a sharp increase in the serum IgG titers in 5 patients, a moderate increase in 1 patient and a plateau in 3 patients. Sero-prevalence of COVID-19 disease in pre-procedure patients was 5.5%. Our findings suggest serological tests can be used for appropriate patient triaging when performed as an adjunct to existing molecular testing.

Early trends for SARS-CoV-2 infection in central and north Texas and impact on other circulating respiratory viruses (preprint)

Introduction: Rapid diagnosis and isolation are key to containing the rapid spread of a pandemic agent like SARS-CoV-2, which has spread globally since its initial outbreak in Wuhan province in China. SARS-CoV-2 is novel to most parts of the world including USA and the effect on normally prevalent viruses is just becoming apparent. We present our initial data on the prevalence of respiratory viruses in the month of March, 2020. Methods: This is a retrospective cohort study post launching of SARS-CoV-2 testing at BSWH, Temple TX. Testing for SARS-CoV-2 was performed by real-time RT-PCR assay and results were shared with State public health officials for immediate interventions. Results: More than 3500 tests were performed during the first two weeks of testing for SARS-CoV-2 and identified 168 (4.7%) positive patients. Sixty-two (3.2%) of the 1,912 ambulatory patients and 106 (6.3%) of the 1,659 ED/inpatients were tested positive. Higher rate of infection (6.9%) were noted in the patients belonging to age group 25-34 years and least number of positive cases were noted in <25 years old (2%) group. The TX State county specific patient demographic information was shared with respective public health departments for epidemiological interventions. Incidentally, this study showed that there was a sudden decrease in the occurrence of other infections due to seasonal viruses, perhaps due to increased epidemiological awareness, about SARS-CoV-2, among general public. Authors would also like to share a small study on SARS-CoV-2 serological assay for the detection of IgG antibodies. Conclusions: This study was intended to provide an initial experience of dealing with a pandemic and the role of laboratories in crisis management. Epidemiological interventions depend on timely availability of accurate diagnostic tests and throughput capacity of such systems during large outbreaks like SARS-CoV-2.