Table 2 Classification of samples by ELISA and Luminex immunoassays for specific IgG, IgM and IgA and percentage of agreement between the tests.

From: Agreement between commercially available ELISA and in-house Luminex SARS-CoV-2 antibody immunoassays

Isotype

Antigen

LM−

E−

LM−

E+

LM+

E −

LM+

E+

Positive agreement (%)

Negative agreement (%)

IgG

N FL

142

10

1

18

62.07

92.81

N CT

130

5

13

23

56.10

87.84

S

132

1

11

27

69

91.67

S2

142

1

1

27

93.10

98.61

RBD

133

1

10

27

71.05

92.36

Combination

121

1

22

27

54.00

84.03

IgM

N FL

25

122

0

24

16.44

17.01

N CT

25

139

0

7

4.79

15.24

S

25

127

0

19

13.01

16.45

S2

24

134

1

12

8.22

15.19

RBD

25

132

0

14

9.59

15.92

Combination

24

112

1

34

23.29

17.65

IgA

N FL

25

121

0

25

17.12

17.12

N CT

25

133

0

13

8.90

15.82

S

22

119

3

27

18.49

15.60

S2

23

115

2

31

21.23

16.67

RBD

23

121

2

25

17.12

15.97

Combination

22

102

3

44

30.14

17.74

  1. The table shows the number of samples classified by the two tests taking into account specific IgG, IgM and IgA against any of the antigens included in the Luminex multiplex panel or the combination of all of them. Concordant samples are those classified as negative (LM− E−) or positive (LM+ E+) by both tests, while discrepant samples are those with opposite results in both tests (LM+ E− and LM− E+). The percentages of agreement were calculated by dividing the concordant positive samples (LM+ E+) or concordant negative samples (LM− E−) by the total of samples that tested positive (LM+ E+, LM+ E−, LM-E+) or negative (LM− E−, LM+ E−, LM− E+) in at least one of the tests, respectively.
  2. LM Luminex, E ELISA.
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