Table 2.
Clinical performance characteristics of LFA in serum to detect SARS-CoV-2 IgM antibodies
| IgM | MedTest | EcoTest | Camtech | |||
|---|---|---|---|---|---|---|
| value | 95% CI | value | 95% CI | value | 95% CI | |
| Group PCR+/PCR– | ||||||
| TP | 68 | 48 | 72 | |||
| Sensitivity, % | 82.93 | 73.02; 90.34 | 58.54 | 47.12; 69.32 | 87.80 | 78.71; 93.99 |
| Specificity, % | 100.00 | 90.51; 100.00 | 83.78 | 67.99; 93.81 | 81.08 | 64.84; 92.04 |
| LR (+) | 32.04 | 4.62; 222.32 | 3.61 | 1.70; 7.68 | 4.64 | 2.37; 9.09 |
| LR (−) | 0.17 | 0.11; 0.28 | 0.49 | 0.37; 0.66 | 0.15 | 0.08; 0.27 |
| DOR | 188.47 | 42.00; 794.00 | 7.37 | 4.60; 11.64 | 30.93 | 29.63; 33.67 |
| Youden's index | 0.83 | 0.64; 0.90 | 0.42 | 0.15; 0.63 | 0.69 | 0.44; 0.86 |
| CUI+ | 0.83 | 0.75; 0.91 | 0.52 | 0.39; 0.65 | 0.80 | 0.72; 0.88 |
| CUI– | 0.73 | 0.64; 0.81 | 0.40 | 0.29; 0.51 | 0.61 | 0.50; 0.72 |
| PPV, % | 100.00 | − | 88.89 | 79.00; 94.45 | 91.14 | 84.01; 95.27 |
| NPV, % | 72.55 | 62.12; 80.98 | 47.69 | 40.47; 55.02 | 75.00 | 62.18; 84.55 |
| Accuracy, % | 88.24 | 81.05; 93.42 | 66.39 | 57.15; 74.78 | 85.71 | 78.12; 91.45 |
| MCC | 0.78 | − | 0.39 | − | 0.68 | − |
| Group PCR+ | ||||||
| TP | 67 | 46 | 66 | |||
| Sensitivity, % | 95.71 | 87.98; 99.11 | 65.71 | 53.40; 76.65 | 94.29 | 86.01; 98.42 |
| Specificity, % | 100.00 | 90.51; 100.00 | 83.78 | 67.99; 93.81 | 81.08 | 64.84; 92.04 |
| LR+ | 36.83 | 5.32; 255.17 | 4.05 | 1.91; 8.59 | 4.98 | 2.55; 9.73 |
| LR– | 0.04 | 0.01; 0.13 | 0.41 | 0.29; 0.58 | 0.07 | 0.03; 0.18 |
| DOR | 921 | 532; 1,962 | 9.87 | 6.59; 14.81 | 71.14 | 85.00; 54.05 |
| Youden's index | 0.96 | 0.79; 0.99 | 0.50 | 0.21; 0.71 | 0.75 | 0.51; 0.91 |
| CUI+ | 0.96 | 0.92; 1.00 | 0.58 | 0.45; 0.71 | 0.85 | 0.78; 0.93 |
| CUI– | 0.93 | 0.87; 0.98 | 0.47 | 0.36; 0.58 | 0.72 | 0.61; 0.82 |
| PPV, % | 100.00 | − | 88.46 | 78.33; 94.21 | 90.41 | 82.84; 94.85 |
| NPV, % | 92.50 | 80.30; 97.39 | 56.36 | 47.55; 64.79 | 88.24 | 74.09; 95.16 |
| Accuracy, % | 97.20 | 92.02; 99.42 | 71.96 | 62.45; 80.22 | 89.72 | 82.35; 94.76 |
| MCC | 0.94 | − | 0.47 | − | 0.77 | − |
| Group PCR– | ||||||
| TP | 01 | 02 | 06 | |||
| Sensitivity, % | 8.33 | 0.21; 38.48 | 16.67 | 2.09; 48.41 | 50.00 | 21.09; 78.91 |
| Specificity, % | 100.00 | 90.51; 100.00 | 83.78 | 67.99; 93.81 | 81.08 | 64.84; 92.04 |
| LR+ | 5.57 | 0.55; 56.78 | 1.03 | 0.24; 4.43 | 2.64 | 1.10; 6.34 |
| LR– | 0.92 | 0.77; 1.09 | 0.99 | 0.74; 1.33 | 0.62 | 0.34; 1.11 |
| DOR | 6.05 | 0.714; 52.09 | 1.04 | 0.32; 3.33 | 4.26 | 3.33; 5.71 |
| Youden's index | 0.08 | −0.09; 0.39 | 0.01 | −0.30; 0.42 | 0.31 | −0.14; 0.71 |
| CUI+ | 0.08 | 0.00; 0.55 | 0.04 | 0.00; 0.35 | 0.23 | 0.0; 0.57 |
| CUI– | 0.77 | 0.69; 0.85 | 0.63 | 0.53; 0.74 | 0.68 | 0.57; 0.78 |
| PPV, % | 100.00 | − | 25.00 | 7.17; 58.98 | 46.15 | 26.33; 67.27 |
| NPV, % | 77.08 | 73.93; 79.96 | 75.61 | 69.88; 80.56 | 83.33 | 73.55; 89.99 |
| Accuracy, % | 77.55 | 63.38; 88.23 | 67.35 | 52.46; 80.05 | 73.47 | 58.92; 85.05 |
| MCC | 0.25 | − | 0.01 | − | 0.30 | − |
LFA, lateral flow immunochromatographic assay; TP, true positive; PPV, positive predictive value; NPV, negative predictive value; LR, likelihood ratio; DOR, diagnostic odds ratio (the higher the DOR value, the better the test); CUI, clinical utility index; MCC, Matthews correlation coefficient.