Refine
Year of publication
- 2021 (2)
Document Type
- Article (2) (remove)
Language
- English (2)
Has Fulltext
- yes (2)
Is part of the Bibliography
- no (2) (remove)
Keywords
- Specificity (2) (remove)
Institute
- Medizin (2)
Background: Antibody detection of SARS-CoV-2 requires an understanding of its variation, course, and duration.
Methods: Antibody response to SARS-CoV-2 was evaluated over 5–430 days on 828 samples across COVID-19 severity levels, for total antibody (TAb), IgG, IgA, IgM, neutralizing antibody (NAb), antibody avidity, and for receptor-binding-domain (RBD), spike (S), or nucleoprotein (N). Specificity was determined on 676 pre-pandemic samples.
Results: Sensitivity at 30–60 days post symptom onset (pso) for TAb-S/RBD, TAb-N, IgG-S, IgG-N, IgA-S, IgM-RBD, and NAb was 96.6%, 99.5%, 89.7%, 94.3%, 80.9%, 76.9% and 92.8%, respectively. Follow-up 430 days pso revealed: TAb-S/RBD increased slightly (100.0%); TAb-N decreased slightly (97.1%); IgG-S and IgA-S decreased moderately (81.4%, 65.7%); NAb remained positive (94.3%), slightly decreasing in activity after 300 days; there was correlation with IgG-S (Rs = 0.88) and IgA-S (Rs = 0.71); IgG-N decreased significantly from day 120 (15.7%); IgM-RBD dropped after 30–60 days (22.9%). High antibody avidity developed against S/RBD steadily with time in 94.3% of patients after 430 days. This correlated with persistent antibody detection depending on antibody-binding efficiency of the test design. Severe COVID-19 correlated with earlier and higher antibody response, mild COVID-19 was heterogeneous with a wide range of antibody reactivities. Specificity of the tests was ≥99%, except for IgA (96%).
Conclusion: Sensitivity of anti-SARS-CoV-2 assays was determined by test design, target antigen, antibody avidity, and COVID-19 severity. Sustained antibody detection was mainly determined by avidity progression for RBD and S. Testing by TAb and for S/RBD provided the highest sensitivity and longest detection duration of 14 months so far.
Background: Testing for COVID-19 with quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) may result in delayed detection of disease. Antigen detection via lateral flow testing (LFT) is faster and amenable to population-wide testing strategies. Our study assesses the diagnostic accuracy of LFT compared to RT-PCR on the same primarycare patients in Austria. Methods: Patients with mild to moderate flu-like symptoms attending a general practice network in an Austrian district (October 22 to November 30, 2020) received clinical assessment including LFT. All suspected COVID-19 cases obtained additional RT-PCR and were divided into two groups: Group 1 (true reactive): suspected cases with reactive LFT and positive RT-PCR; and Group 2 (false non-reactive): suspected cases with a non-reactive LFT but positive RT-PCR. Findings: Of the 2,562 symptomatic patients, 1,037 were suspected of COVID-19 and 826 (79.7%) patients tested RT-PCR positive. Among patients with positive RT-PCR, 788/826 tested LFT reactive (Group 1) and 38 (4.6%) non-reactive (Group 2). Overall sensitivity was 95.4% (95%CI: [94%,96.8%]), specificity 89.1% (95%CI: [86.3%, 91.9%]), positive predictive value 97.3% (95%CI:[95.9%, 98.7%]) and negative predictive value 82.5% (95%CI:[79.8%, 85.2%]). Reactive LFT and positive RT-PCR were positively correlated (r = 0.968,95CI=[0.952,0.985] and κ=0.823, 95%CI=[0.773,0.866]). Reactive LFT was negatively correlated with Ct-value (r = -0.2999,p < 0.001) and pre-test symptom duration (r = -0.1299,p = 0.0043) while Ct-value was positively correlated with pre-test symptom duration (r = 0.3733),p < 0.001). Interpretation: We show that LFT is an accurate alternative to RT-PCR testing in primary care. We note the importance of administering LFT properly, here combined with clinical assessment in symptomatic patients.