Table 1.
Negative serum sample panel consisting of samples collected retrospectively during years 2018-2019, prior the SARS-CoV-2 epidemic.
| Number and type of samples (serum) |
aAbbott, IgG, nucleoprotein antigen (INDEX) | bEuroimmun, IgA, S1 antigen (ratio) | bEuroimmun, IgG, S1 antigen (ratio) | cLiaison, IgG, S1/S2 antigen (AU/mL) | dAcro IgG/IgM (x/x), pos or neg | eXiamen Biotime IgG/IgM (x/x), pos or neg | fMNT (titer) | |
|---|---|---|---|---|---|---|---|---|
| Nuclear Ab, pattern (titer)1 Rf (+/-)1 | ||||||||
| 1 | homogeneous (1280), Rf(-) | NEG (0.03) | NEG (0.59) | NEG (0.35) | NEG (0.95) | pos/pos | neg/neg | <40 |
| 2 | homogeneous (1280,) Rf(-) | NEG (0.07) | NEG (0.20) | NEG (0.43) | NEG (2.38) | pos/pos | neg/neg | <40 |
| 3 | homogeneous (>5000), Rf(-) | NEG (0.09) | INCONC.(1.05) | NEG (0.31) | INCONC.(13.2) | pos/pos | neg/neg | <40 |
| 4 | homogeneous (1280), Rf(-) | NEG (0.31) | NEG (0.54) | NEG (0.58) | NEG (3.02) | pos/neg | neg/neg | <40 |
| 5 | homogeneous (>5000), Rf(-) | NEG (0.06) | NEG (0.15) | INCONC.(0.93) | NEG (5.25) | pos/neg | neg/neg | <40 |
| 6 | homogeneous (1280,) Rf(-) | NEG (0.04) | INCONC.(0.99) | NEG (0.44) | NEG (2.56) | neg/neg | neg/neg | <40 |
| 7 | homogeneous (1280), Rf(-) | NEG (0.03) | POS (2.45) | POS (1.13) | Invalid result | neg/neg | pos/pos | <40 |
| 8 | speckled (>5000), Rf(-) | NEG (0.13) | NEG (0.39) | NEG (0.31) | NEG (2.25) | neg/neg | neg/neg | <40 |
| 9 | speckled (1280), Rf(-) | NEG (0.09) | NEG (0.55) | NEG (0.28) | NEG (3.38) | neg/neg | neg/neg | <40 |
| 10 | speckled (>5000), Rf(-) | NEG (0.03) | POS (1.12) | NEG (0.41) | NEG (2.56) | neg/neg | neg/neg | <40 |
| 11 | speckled (1280), Rf(+) | NEG (0.06) | NEG (0.69) | NEG (0.61) | NEG (6.91) | neg/neg | neg/neg | <40 |
| 12 | speckled (1280), Rf(-) | POS (1.82) | NEG (0.21) | NEG (0.38) | NEG (2.28) | neg/neg | neg/neg | <40 |
| 13 | speckled (1280), Rf(-) | NEG (0.04) | INCONC.(0.96) | NEG (0.61) | NEG (3.01) | neg/neg | neg/neg | <40 |
| 14 | speckled (>5000), Rf(+) | NEG (0.02) | NEG (0.31) | NEG (0.33) | NEG (4.30) | neg/neg | neg/neg | <40 |
| 15 | Centromere + AMA (1280), Rf(-) | NEG (0.02) | NEG (0.15) | NEG (0.29) | NEG (2.06) | neg/neg | neg/neg | <40 |
| 16 | centromere (1280), Rf(-) | NEG (0.07) | POS (9.42) | NEG (0.64) | NEG (1.50) | neg/neg | neg/neg | <40 |
| 17 | centromere (1280), Rf(-) | NEG (0.01) | INCONC.(1.01) | NEG (0.68) | NEG (3.12) | neg/neg | neg/neg | <40 |
| 18 | centromere (1280), Rf(-) | NEG (0.01) | NEG (0.16) | NEG (0.24) | NEG (3.22) | neg/neg | neg/neg | <40 |
| 19 | centromere (1280), Rf(-) | NEG (0.02) | NEG (0.07) | NEG (0.23) | POS (35.5) | neg/neg | neg/neg | <40 |
| 20 | nucleolar. (80), Rf(-) | NEG (0.02) | NEG (0.47) | NEG (0.28v | NEG (1.28) | pos/neg | neg/neg | <40 |
| 21 | speckled (5000) and nuclear dots (1280), Rf(-) | NEG (0.39) | NEG (0.20) | NEG (0.32) | NEG (4.31) | neg/pos | neg/neg | <40 |
| Phospolipase receptor 2A pos (titer)1, Rf(+/-)1 | 20/21 neg | 14/21 neg | 19/21 neg | 18/21 neg | 14/21 neg | 20/21 neg | ||
| 1 | 50, Rf(-) | NEG (0.04) | NEG (0.13) | NEG (0.20 | NEG (1.49) | neg/neg | neg/neg | <40 |
| 2 | 50, Rf(-) | NEG (0.01) | NEG (0.17) | NEG (0.19 | NEG (2.43) | pos/pos | neg/neg | <40 |
| 3 | 50, Rf(-) | NEG (0.06) | NEG (0.11) | NEG (0.22 | NEG (0.96) | neg/neg | neg/neg | <40 |
| 4 | 50, Rf(-) | NEG (0.03) | NEG (0.42) | NEG (0.21 | NEG (2.11) | neg/pos | neg/pos | <40 |
| 5 | 50, Rf(-) | NEG (0.03) | POS (2.06) | NEG (0.37 | NEG (3.51) | pos/pos | neg/pos | <40 |
| 6 | 50, Rf(-) | NEG (0.05) | NEG (0.46) | NEG (0.31 | NEG (1.64) | neg/pos | neg/neg | <40 |
| 7 | 250, Rf(-) | NEG (0.02) | NEG (0.21) | NEG (0.21 | NEG (1.49) | neg/neg | neg/neg | <40 |
| 8 | 50, Rf(-) | NEG (0.01) | NEG (0.30) | NEG (0.41 | NEG (0.93) | pos/neg | neg/neg | <40 |
| 9 | 50, Rf(-) | NEG (0.01) | NEG (0.11 | NEG (0.16 | NEG (0.27) | pos/neg | neg/neg | <40 |
| 10 | 50, Rf(+) | NEG (0.15) | NEG (0.26 | NEG (0.32 | NEG (1.69) | neg/neg | neg/neg | <40 |
| GBM Ab pos (titer)1, Rf(+/-)1 | 10/10 neg | 9/10 neg | 10/10 neg | 10/10 neg | 4/10 neg | 8/10 neg | ||
| 1 | 250, Rf(+) | NEG (0.04) | NEG (0.18) | NEG (0.24) | NEG (3.02) | neg/neg | neg/neg | <40 |
| 2 | 250, Rf(-) | NEG (0.04) | NEG (0.19) | NEG (0.32) | Invalid result | neg/neg | neg/neg | <40 |
| 3 | 50, Rf(-) | NEG (0.14) | NEG (0.35) | NEG (0.23) | NEG (2.50) | neg/pos | neg/neg | <40 |
| ANCA Ab pos (titer)1, Rf(+/-)1 | 3/3 neg | 3/3 neg | 3/3 neg | 2/3 neg | 2/3 neg | 3/3 neg | ||
| 1 | atypical C-ANCA (50), Rf(-) | NEG (0.10) | NEG (0.69) | NEG (0.45) | NEG (3.73) | neg/neg | neg/neg | <40 |
| 2 | C-ANCA (1280), Rf(-) | NEG (0.12) | NEG (0.44) | NEG (0.30) | NEG (4.34) | neg/neg | neg/neg | <40 |
| 3 | P-ANCA (200), Rf(-) | NEG (0.03) | NEG (0.28) | NEG (0.24) | Invalid result | neg/neg | neg/neg | <40 |
| 4 | C-ANCA (50), P-ANCA (1280), Rf(-) | NEG (0.07) | NEG (0.28) | NEG (0.31) | NEG (2.20) | neg/neg | neg/neg | <40 |
| 5 | P-ANCA (200), Rf(+) | NEG (0.07) | NEG (0.13) | NEG (0.23) | NEG (3.02) | pos/pos | neg/neg | <40 |
| Primary EBV infection (IgG, IgM, AVI)2 | 5/5 neg | 5/5 neg | 5/5 neg | 4/5 neg | 4/5 neg | 5/5 neg | ||
| 1 | POS, POS, LOW | NEG (0.07) | NEG (0.73) | INCONC.(1.09) | NEG (3.71) | pos/pos | neg/pos | <40 |
| 2 | POS, POS, LOW | NEG (0.02) | NEG (0.32) | NEG (0.33) | NEG (1.83) | neg/pos | neg/pos | <40 |
| 3 | POS, POS, LOW | NEG (0.09) | INCONC.(0.82) | INCONC.(0.96) | NEG (1.86) | neg/pos | neg/neg | <40 |
| HCoV samples3 | 3/3 neg | 2/3 neg | 1/3 neg | 3/3 neg | 0/3 neg | 1/3 neg | ||
| 1 | HCoV OC43 | NEG (0.05) | INCONC.(0.97) | NEG (0.13) | NEG (3.97) | neg/neg | neg/neg | <40 |
| 2 | HCoV OC43 | NEG (0.02) | NEG (0.09) | NEG (013) | NEG (2.33) | pos/neg | neg/neg | <40 |
| 3 | HCoV OC43 | NEG (0.05) | NEG (0.25) | NEG (0.17) | NEG (2.39) | neg/neg | neg/neg | <40 |
| 4 | HCoV OC43 | NEG (0.08) | POS (1.22) | POS (2.54) | NEG (2.20) | neg/neg | neg/neg | <40 |
| Samples from year 20194 | 4/4 neg | 2/4 neg | 3/4 neg | 4/4 neg | 4/4 neg | 4/4 neg | ||
| 1 | NEG (0.04) | POS (5.12) | INCONC.(1.07) | NEG (2.19) | neg/neg | neg/neg | <40 | |
| 2 | NEG (0.02) | NEG (0.23) | NEG (0.16) | POS (17.8) | neg/neg | neg/neg | <40 | |
| 3 | NEG (0.15) | NEG (0.43) | NEG (0.30) | POS (16.0) | neg/pos | neg/neg | <40 | |
| 4 | NEG (0.07) | INCONC.(1.07) | INCONC.(0.96) | NEG (3.27) | neg/neg | neg/neg | <40 | |
| 5 | NEG (0.02) | POS (1.73) | POS (5.71) | NEG (2.44) | neg/pos | neg/pos | <40 | |
| 6 | NEG (0.03) | POS (1.25) | POS (2.42) | NEG (2.47) | pos/neg | nd/nd | <40 | |
| 7 | NEG (0.02) | POS (4.51) | POS (1.70) | NEG (1.70) | pos/pos | nd/nd | <40 | |
| 8 | NEG (0.04) | POS (1.52) | NEG (0.28) | NEG (1.89) | nd/nd | nd/nd | nd | |
| 9 | NEG (0.11) | NEG (0.23) | NEG (0.35) | NEG (3.73) | nd/nd | nd/nd | nd | |
| 10 | NEG (0.07) | NEG (0.28) | NEG (0.29) | NEG (3.25) | nd/nd | nd/nd | nd | |
| 11 | NEG (0.03) | NEG (0.48) | NEG (0.76) | NEG (5.76) | nd/nd | nd/nd | nd | |
| 12 | NEG (0.01) | NEG (0.25) | NEG (0.29) | NEG (2.11) | nd/nd | nd/nd | nd | |
| 13 | NEG (0.04) | NEG (0.18) | NEG (0.14) | NEG (1.59) | nd/nd | nd/nd | nd | |
| 14 | NEG (0.11) | POS (7.96) | NEG (0.60) | NEG (3.02) | nd/nd | nd/nd | nd | |
| 15 | NEG (0.03) | INCONC.(1.02) | NEG (0.31) | NEG (2.72) | nd/nd | nd/nd | nd | |
| 16 | NEG (0.02) | NEG (0.09) | NEG (0.25) | NEG (5.60) | nd/nd | nd/nd | nd | |
| 17 | NEG (0.02) | NEG (0.42) | NEG (0.27) | NEG (1.48) | nd/nd | nd/nd | nd | |
| 18 | NEG (0.02) | NEG (0.17) | NEG (0.22) | NEG (1.32) | nd/nd | nd/nd | nd | |
| 19 | NEG (0.02) | NEG (0.56) | NEG (0.23) | NEG (2.13) | nd/nd | nd/nd | nd | |
| 20 | NEG (0.02) | NEG (0.39) | NEG (0.20) | NEG (2.86) | nd/nd | nd/nd | nd | |
| 21 | NEG (0.02) | NEG (0.26) | NEG (0.18) | NEG (1.15) | nd/nd | nd/nd | nd | |
| 22 | NEG (0.02) | NEG (0.77) | NEG (0.18) | NEG (1.00) | nd/nd | nd/nd | nd | |
| 23 | NEG (0.01) | NEG (0.73) | NEG (0.13) | NEG (1.04) | nd/nd | nd/nd | nd | |
| 24 | NEG (0.03) | NEG (0.43) | NEG (0.32) | NEG (2.36) | nd/nd | nd/nd | nd | |
| 25 | POS (2.09) | NEG (0.35) | NEG (0.21) | NEG (1.64) | nd/nd | nd/nd | nd | |
| 26 | NEG (0.01) | NEG (0.21) | NEG (0.15) | NEG (2.04) | nd/nd | nd/nd | nd | |
| 27 | NEG (0.10) | POS (6.82) | NEG (0.44) | NEG (1.54) | nd/nd | nd/nd | nd | |
| 28 | NEG (0.02) | POS (1.52) | NEG (0.71) | NEG (5.75) | nd/nd | nd/nd | nd | |
| 29 | NEG (0.04) | POS (1.80) | NEG (0.21) | NEG (5.41) | nd/nd | nd/nd | nd | |
| 30 | NEG (0.05) | NEG (0.61) | NEG (0.30) | NEG (2.69) | nd/nd | nd/nd | nd | |
| 31 | NEG (0.01) | NEG (0.75) | NEG (0.30) | NEG (2.26) | nd/nd | nd/nd | nd | |
| 32 | NEG (0.01) | NEG (0.16) | NEG (0.21) | NEG (1.28) | nd/nd | nd/nd | nd | |
| 33 | NEG (0.03) | NEG (0.77) | NEG (0.29) | NEG (2.87) | nd/nd | nd/nd | nd | |
| 34 | NEG (0.01) | NEG (0.08) | NEG (0.14) | NEG (0.73) | nd/nd | nd/nd | nd | |
| 35 | NEG (0.04) | NEG (0.23) | NEG (0.29) | NEG (1.70) | nd/nd | nd/nd | nd | |
| 34/35 neg | 24/35 neg | 30/35 neg | 33/35 neg | 3/7 neg | 4/5 neg | |||
| Specificity % | 97.5 % | 75.3 % | 87.7 % | 91.4 % | 30/53 neg | 45/51 neg | ||
| Assay process successful % of samples | 100 % | 100 % | 100 % | 96.3 % | ||||
Neg, negative; pos, positive; inconc., inconclusive; nd, not determined; Rf (-), rheumatoid factor negative; Rf(+), rheumatoid factor positive; PLA2R, phospolipase A2 receptor; GBM, glomerular basement membrane; ANCA, antineutrophil cytoplasmic antibodies; EBV, Epstein-Barr virus; MNT, microneutralisation assay.
Nuclear, phospholipase A2 receptor (PLA2R), glomerular basement membrane (GBM), antineutrophil cytoplasmic (ANCA) antibodies were detected using immunofluorescence assays of NOVA Lite® DAPI ANA Kit (Inova Diagnostics, California, USA), Anti-Phospholipase A2 Receptor IIFT (IgG) (Euroimmun, Lübeck, Germany), EUROPLUS kidney (monkey) and GBM antigen IIFT (Euroimmun, Lübeck, Germany) and NOVA Lite® ANCA IFA Kit (Inova Diagnostics, California, USA), respectively. Rheumatoid factors (Rf) were determined using RapiTex® RF (Siemens Healthcare Diagnostics, Erlangen, Germany).
EBV IgG and IgM were determined using Enzygnost Anti-EBV/IgG and Anti-EBV/IgM II (Siemens Healthcare Diagnostics, Erlangen, Germany).
HCoV were detected using xTAG® Respiratory Viral panel kit (Luminex Corporation, Texas, USA) from nasopharyngeal samples and corresponding serum samples taken from the patient were used for testing antibodies.
All serum samples were sent for antibody testing of influenza A, B, respiratory syncytial virus, parainfluenza virus, enterovirus IgG antibodies (HUSLAB, Finland) in 2019.
Architect SARS-CoV-2 IgG Assay (Abbott, Illinois, USA).
Anti-SARS-CoV-2 IgA and IgG EIA (Euroimmun, Lübeck, Germany).
LIAISON® SARS-CoV-2 IgG (DiaSorin, Saluggia, Italy).
2019-nCoV IgG/IgM Rapid Test Cassette (Acro Biotech, California, USA).
SARS-CoV-2 IgG/IgM Rapid Test (Xiamen Biotime, Fujian, China).
Microneutralisation assay were carried out according protocol described by Haveri et al. (2020).