Table 1.

Positive rate of Abbott semi-quantitative anti-RBD, Abbott qualitative anti-NP, and EUROIMMUN (EI) anti-S1 assays. N: number of specimens for each time period.

Time after symptom onset	Abbott anti-RBD	n	Abbott anti-NP	n	EI anti-S1	n
<3 d	0.0%	14	0%	14	0%	14
3-7d	39.7%	116	29.10%	110	27.60%	123
8-14d	75.9%	340	69.50%	367	61.10%	357
15-21d	95.6%	250	93.60%	297	89.60%	297
4-5w	98.7%	239	99.60%	248	93.60%	235
6-7w	99.4%	175	99.40%	179	98.30%	176
8-9w	100%	66	97.20%	71	98.50%	68
10w- < 3 m	100%	34	97.10%	34	100%	35
3 m- < 5 m	100%	9	88.90%	9	100%	8
5 + m	100%	10	85.7%	7	100%	6