Table 2 Evaluation of assay performance.

From: Evaluation and deployment of isotype-specific salivary antibody assays for detecting previous SARS-CoV-2 infection in children and adults

Assay

Pre-pandemic (N)

PCR-confirmed (N)

Threshold method

Threshold value

AUC (%)

95% CI

False positives (N)

Specificity (%)

95% CI

False negatives (N)

Sensitivity (%)

95% CI

N-protein IgA

173

81

97th percentile

0.524

71.9

65.7–78.1

6

96.5

93.6–98.8

74

8.64

3.7–14.8

N-protein IgG

173

80

98th percentile

0.484

84.6

79.9–89.4

3

98.3

95.9–100

66

17.5

10–26.2

Spike IgA

223

87

99th percentile

0.384

89.9

86.5–93.2

5

97.7

95.5–99.5

55

36.8

26.4–47.1

Spike IgG

197

83

98th percentile

0.306

95.0

92.8–97.3

3

99.0

97.4–100

41

50.6

39.8–61.4

  1. Performance of N-protein and spike IgA and IgG assays was evaluated using known negative (pre-pandemic) and known positive (PCR-confirmed) samples in combined threshold and validation sets combined. Normalised OD was used as input value in ROC analysis. AUC = Area under the ROC curve. 95% CI = 95% confidence interval calculated for AUC using DeLong’s method or computed with 10,000 stratified bootstrap replicates for sensitivity and specificity estimates.
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