Clinical Utility of a Highly Sensitive Lateral Flow Immunoassay as determined by Titer Analysis for the Detection of anti-SARS-CoV-2 Antibodies at the Point-of-Care

Abstract

Coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), became a pandemic in early 2020. Lateral flow immunoassays for antibody testing have been viewed as a cheap and rapidly deployable method for determining previous infection with SARS-CoV-2; however, these assays have shown unacceptably low sensitivity. We report on nine lateral flow immunoassays currently available and compare their titer sensitivity in serum to a best-practice enzyme-linked immunosorbent assay (ELISA) and viral neutralization assay. For a small group of PCR-positive, we found two lateral flow immunoassay devices with titer sensitivity roughly equal to the ELISA; these devices were positive for all PCR-positive patients harboring SARS-CoV-2 neutralizing antibodies. One of these devices was deployed in Northern Italy to test its sensitivity and specificity in a real-world clinical setting. Using the device with fingerstick blood on a cohort of 27 hospitalized PCR-positive patients and seven hospitalized controls, ROC curve analysis gave AUC values of 0.7646 for IgG. For comparison, this assay was also tested with saliva from the same patient population and showed reduced discrimination between cases and controls with AUC values of 0.6841 for IgG. Furthermore, during viral neutralization testing, one patient was discovered to harbor autoantibodies to ACE2, with implications for how immune responses are profiled. We show here through a proof-of-concept study that these lateral flow devices can be as analytically sensitive as ELISAs and adopted into hospital protocols; however, additional improvements to these devices remain necessary before their clinical deployment.

Suitability of two rapid lateral flow immunochromatographic assays for predicting SARS‐CoV‐2 neutralizing activity of sera

“…A handful of studies have compared the performance of LFIC assays versus SARS‐CoV‐2 neutralization assays, 9–12 but none of the LFIC evaluated herein was included. These studies differed in many aspects, namely, the timing of sera collection, clinical presentation of COVID‐19, neutralization antibody assay employed, NtAb 50 titer cutoff value for positive results, and the reference method for sensitivity calculations (either the NtAb assay itself or RT‐PCR results).…”

“…Unfortunately, virus neutralization assays, whether using wild‐type SARS‐CoV‐2, engineered SARS‐CoV‐2 pseudotypes, or chimeric viruses, 8 are unsuited for routine testing, thus creating a need to assess commercial SARS‐CoV‐2 immunoassays for their capacity to provide reliable information on sera neutralizing activity. Several studies have evaluated the performance of LFIC in comparison with NtAb assays in subjects with past or ongoing SARS‐CoV‐2 infection 9–12 . Nevertheless, to the best of our knowledge, only one has attempted to quantitatively correlate results yielded by the two assay types by analyzing the strength of test line reactivity in LFIC devices and NtAb 50 titers 9 …”

Suitability of Two Rapid Lateral Flow Immunochromatographic Assays for Predicting SARS-CoV-2 Neutralizing Activity of Sera

“…A handful of studies have compared the performance of LFIC assays versus SARS-CoV-2 neutralization assays [9-12], but none of the LFIC evaluated herein were included. These studies differed in many aspects, namely, the timing of sera collection, clinical presentation of COVID-19, neutralization antibody assay employed, NtAb 50 titer cutoff value for positive results, and the reference method for sensitivity calculations (either the NtAb assay itself or RT-PCR results).…”

“…Unfortunately, virus neutralization assays, whether using wild-type SARS-CoV-2, engineered SARS-CoV-2 pseudotypes or chimeric viruses [8] are unsuited for routine testing, thus creating a need to assess commercial SARS-CoV-2 immunoassays for their capacity to provide reliable information on sera neutralizing activity. Several studies have evaluated the performance of LFIC in comparison with NtAb assays in subjects with past or ongoing SARS-CoV-2 infection [9-12]. Nevertheless, to the best of our knowledge, only one has attempted to quantitatively correlate results yielded by the two assay types by analyzing the strength of test line reactivity in LFIC devices and NtAb 50 titers [11].…”

Emerging point-of-care biosensors for rapid diagnosis of COVID-19: current progress, challenges, and future prospects

“…There is also a control line coated with goat anti-rabbit IgG. The clinical sensitivity and specificity of the kit are 93% and 96%, respectively [168]. Abbexa's COVID-19 IgG/IgM rapid testing kit was used to detect IgG/ IgM, producing test results in 10 min.…”