Table 4.

Assay sensitivities by days post symptom onset.

Assay	Days PSO	Total No. of PCR-positive samples	No. testing positive	Percentage	95% CI
Epitope IgG	<8 days	26	11	42.31	25.54–61.05
	8–14 days	77	65	84.42	74.71–90.85
	15–21 days	65	60	92.31	83.22–96.67
	>21 days	83	71	85.54	76.41–91.53
	Overall	251	207	82.47	77.29–86.67
Epitope IgM	<8 days	26	8	30.77	16.50–49.99
	8–14 days	77	43	55.84	44.74–66.39
	15–21 days	65	41	63.08	50.92–73.77
	>21 days	83	26	31.33	22.36–41.94
	Overall	251	118	47.01	40.93–53.18
Ragon/MGH IgGa	<8 days	26	5	19.23	8.51–37.88
	8–14 days	77	44	57.14	46.01–67.60
	15–21 days	65	52	80.00	68.73–87.92
	>21 days	83	61	73.49	63.11–81.80
	Overall	251	162	64.54	58.45–70.20
Rocheb	<8 days	26	13	50.00	32.06–67.94
	8–14 days	77	62	80.52	70.31–87.82
	15–21 days	65	59	90.77	81.29–95.70
	>21 days	83	74	89.16	80.66–94.19
	Overall	251	208	82.87	77.72–87.03
Simoa (Early)c	<8 days	26	15	57.69	38.95–74.46
	8–14 days	77	72	93.51	85.68–97.19
	15–21 days	65	65	100.00	94.42–100.00
	>21 days	83	79	95.18	88.25–98.11
	Overall	251	231	92.03	88.01–94.78

^aFor sensitivity of Ragon/MGH IgM and IgA see Supplemental Materials.

^bThe Roche Elecsys Anti-SARS-CoV-2 immunoassay detects IgG and likely IgM and IgA; details of other isotypes are not provided by the manufacturer.

^cSensitivity of the Simoa multiplex assay Early Model. For sensitivities of the Late and 12-Parameter Models, see Supplementary Materials.