| Index tests |
2 Ab tests, blinding NR; this entry (Liu 2020b [B]) refers to test [B] in the list below
Laboratory‐based evaluations of ELISA assays measuring IgM and IgG using serum samples
A. rN‐based ELISA ( Lizhu, Zhuhai, China), using recombinant N protein
B. rS‐based ELISA (Hotgen, Beijing, China), using receptor‐binding domain of the recombinant S polypeptide (rS)
Test thresholds:
A. cut‐off calculated by summing 0.100 (IgM) or 0.130 (IgG) and the average A450 of negative control replicates. When A450 < cut‐off value, the test was considered negative, and when A450 was ≥ cut‐off value, the test was considered positive.
B. cut‐off values (IgM and IgG) calculated by summing 0.250 and the average A450 of negative control replicates. When A450 < cut‐off value, the test was considered negative, and when A450 was ≥ cut‐off value, the test was considered positive.
Samples acquired 0‐5 d 22, 10%; 6‐10 d 38, 18%; 11‐15 d 54, 25%; 16‐20 d 55, 26%; ≥ 21 d 45, 21% (32/45 were d 21‐30). Person applying the test not described |
