Appendix 4.

Factors associated with Abbott SARS-CoV-2 IgG seronegativity, among participants who had a previously PCR-confirmed infection, including those who had a grayzone result

Parameter	All participants (n)	Negative result		Unadjusted			Adjusted
		n	%	OR	95% CI	P valuea	OR	95% CI	P valuea
Total	367	124	33.8
Age group
18–29	111	41	36.9	*b			*
30–39	108	43	39.8	1.13	0.66–1.95	0.662	0.96	0.51–1.8	0.893
40–49	79	17	21.5	0.47	0.24–0.89	0.024	0.44	0.21–0.92	0.031
50–59	50	19	38.0	1.05	0.52–2.08	0.897	1.05	0.47–2.36	0.897
60+	19	4	21.1	0.46	0.12–1.35	0.187	0.32	0.08–1.11	0.090
Sex
Female	269	102	37.9	*			*
Male	98	22	22.4	0.47	0.28–0.81	0.006	0.38	0.21–0.68	0.001
Ethnicity
Irish (white)	237	94	39.7	*			*
Any other white background	44	12	27.3	0.57	0.27–1.14	0.123	0.64	0.29–1.39	0.273
Any Asian background	72	14	19.4	0.37	0.19–0.68	0.002	0.41	0.19–0.81	0.012
Any African/black background	10	2	20.0	0.38	0.05–1.56	0.228	0.48	0.07–2.29	0.392
Other	4	2	50.0	1.52	0.18–12.9	0.677	1.53	0.15–15.7	0.705
Close contact with a case of COVID-19c
Yes	211	65	30.8	0.72	0.46–1.11	0.147	0.67	0.4–1.12	0.127
No	154	59	38.3	*			*
Main type of patient contactd
No patient contact	61	24	39.3	*			*
Daily contact non-COVID-19 patients	218	74	33.9	0.79	0.44–1.43	0.435	0.78	0.4–1.56	0.484
Daily contact known or suspected COVID-19 patients	88	26	29.5	0.65	0.21–0.32	0.214	0.84	0.38–1.89	0.679
Severity of symptomsc
No symptoms	7	3	42.9	1.08	0.21–5.05	0.925	1.07	0.17–6.16	0.942
Minor symptoms	151	62	41.1	*			*
Significant symptoms	178	55	30.9	0.64	0.41–1.01	0.056	0.58	0.34–0.96	0.037
Severe symptoms (hospitalized)	29	4	13.8	0.23	0.06–0.63	0.009	0.26	0.07–0.76	0.023
HCW role
Administration	24	9	37.5	*			Not included in the model
Allied health care	42	19	45.2	1.38	0.49–3.94	0.541
General support	12	5	41.7	1.19	0.28–4.92	0.809
Health care assistant	32	5	15.6	0.31	0.08–1.06	0.068
Medical/dental	73	29	39.7	1.10	0.43–2.9	0.846
Nursing/midwifery	181	55	30.4	0.73	0.31–1.83	0.481
Other	3	2	66.7	3.33	0.28–78.0	0.353
No. of mo since PCR positive testc
Less than 1	8	1	12.5	NA	NA	NA	0.23	0.01–1.6	0.204
1	8	0	0.0	NA	NA	NA	NA	NA	NA
2	4	0	0.0	NA	NA	NA	NA	NA	NA
3	1	0	0.0	NA	NA	NA	NA	NA	NA
4	12	0	0.0	NA	NA	NA	NA	NA	NA
5	85	23	27.1	*			*
6	222	91	41.0	1.87	1.09–3.29	0.025	1.95	1.07–3.64	0.032
7	25	9	36.0	1.52	0.57–3.87	0.389	2.07	0.72–5.9	0.172

^aP values were calculated using the chi-square test, results for significant associations are highlighted in bold.

^b*, reference category.

^cExcludes two unknowns.

^dParticipants were asked which type of patient contact describes most of their current work (excludes 5 unknowns).