Table 3.
Clinical performance characteristics of LFA in serum to detect SARS-CoV-2 IgG antibodies
| IgG | MedTest | EcoTest | Camtech | |||
|---|---|---|---|---|---|---|
| value | 95% CI | value | 95% CI | value | 95% CI | |
| Group PCR+/PCR– | ||||||
| TP | 59 | 63 | 59 | |||
| Sensitivity, % | 78.67 | 67.68; 87.29 | 84.00 | 73.72; 91.45 | 78.67 | 67.68; 87.29 |
| Specificity, % | 100.00 | 90.51; 100.00 | 89.19 | 74.58; 96.97 | 97.30 | 85.84; 99.93 |
| LR+ | 30.39 | 4.37; 211.13 | 7.77 | 3.06; 19.71 | 29.11 | 4.20; 201.92 |
| LR– | 0.21 | 0.14; 0.33 | 0.18 | 0.11; 0.30 | 0.22 | 0.14; 0.34 |
| DOR | 144 | 31.21; 639 | 43.17 | 27.82; 65.70 | 132.32 | 30; 594 |
| Youden's index | 0.79 | 0.58; 0.87 | 0.73 | 0.48; 0.88 | 0.76 | 0.54; 0.87 |
| CUI+ | 0.79 | 0.70; 0.88 | 0.79 | 0.70; 0.88 | 0.77 | 0.68; 0.87 |
| CUI– | 0.70 | 0.61; 0.79 | 0.65 | 0.55; 0.76 | 0.67 | 0.58; 0.77 |
| PPV, % | 100.00 | − | 94.03 | 86.13; 97.56 | 98.33 | 89.48; 99.76 |
| NPV, % | 69.81 | 59.96; 78.12 | 73.33 | 61.80; 82.38 | 69.23 | 59.22; 77.71 |
| Accuracy, % | 85.71 | 77.84; 91.61 | 85.71 | 77.84; 91.61 | 84.82 | 76.81; 90.90 |
| MCC | 0.74 | − | 0.70 | − | 0.72 | − |
| Group PCR+ | ||||||
| TP | 58 | 62 | 57 | |||
| Sensitivity, % | 87.88 | 77.51; 94.62 | 93.94 | 85.20; 98.32 | 86.36 | 75.69; 93.57 |
| Specificity, % | 100.00 | 90.51; 100.00 | 89.19 | 74.58; 96.97 | 97.30 | 85.84; 99.93 |
| LR+ | 33.84 | 4.88; 234.75 | 8.69 | 3.44; 21.97 | 31.95 | 4.61; 221.41 |
| LR– | 0.12 | 0.06; 0.23 | 0.07 | 0.03; 0.18 | 0.14 | 0.08; 0.26 |
| DOR | 282 | 81.33; 1,020.00 | 124 | 115; 122 | 228 | 7.62; 850 |
| Youden's index | 0.88 | 0.68; 0.95 | 0.83 | 0.60; 0.95 | 0.84 | 0.62; 0.94 |
| CUI+ | 0.88 | 0.81; 0.95 | 0.88 | 0.81; 0.95 | 0.85 | 0.77; 0.93 |
| CUI– | 0.82 | 0.75; 0.90 | 0.80 | 0.71; 0.88 | 0.78 | 0.70; 0.86 |
| PPV, % | 100.00 | − | 93.94 | 85.98; 97.51 | 98.28 | 89.16; 99.75 |
| NPV, % | 82.22 | 70.72; 89.85 | 89.19 | 76.02; 95.55 | 80.00 | 68.50; 88.04 |
| Accuracy, % | 92.23 | 85.27; 96.59 | 92.23 | 85.27; 96.59 | 90.29 | 82.87; 95.25 |
| MCC | 0.85 | − | 0.83 | − | 0.81 | − |
| Group PCR– | ||||||
| TP | 01 | 01 | 02 | |||
| Sensitivity, % | 11.11 | 0.28; 48.25 | 11.11 | 0.28; 48.25 | 22.22 | 2.81; 60.01 |
| Specificity, % | 100.00 | 90.51; 100.00 | 89.19 | 74.58; 96.97 | 97.30 | 85.84; 99.93 |
| LR+ | 7.09 | 0.71; 71.11 | 1.03 | 0.13; 8.12 | 8.22 | 0.83; 80.97 |
| LR– | 0.89 | 0.71; 1.12 | 1.00 | 0.77; 1.29 | 0.80 | 0.56; 1.14 |
| DOR | 7.97 | 1.00; 63.49 | 1.03 | 0.17; 6.30 | 10.28 | 1.48; 71.03 |
| Youden's index | 0.11 | −0.09; 0.48 | 0.003 | −0.25; 0.45 | 0.20 | −0.11; 0.60 |
| CUI+ | 0.11 | 0.00; 0.65 | 0.02 | 0.00; 0.35 | 0.15 | 0.00; 0.64 |
| CUI– | 0.82 | 0.75; 0.90 | 0.72 | 0.62; 0.81 | 0.82 | 0.74; 0.89 |
| PPV, % | 100.00 | − | 20.00 | 3.07; 66.38 | 66.67 | 16.88; 95.17 |
| NPV, % | 82.22 | 78.59; 85.35 | 80.49 | 76.14; 84.21 | 83.72 | 78.32; 87.98 |
| Accuracy, % | 82.61 | 68.58; 92.18 | 73.91 | 58.87; 85.73 | 82.61 | 68.58; 92.18 |
| MCC | 0.30 | − | 0.003 | − | 0.31 | − |
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.