Performance evaluation of a Sars-CoV-2 rapid test and two automated immunoassays

Castejon, Márcia J.; Yamashiro, Rosemeire; Oliveira, Elaine L.; Silveira, Edilene R. P.; Hong, Marisa A.; Oliveira, Carmem Aparecida F.; Silva, Valéria O.; Ahagon, Cintia M.; Lima, Ana Késia S.; Lindoso, José Angelo L.; Brígido, Luís Fernando M.

doi:10.5935/1676-2444.20210040

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ORIGINAL ARTICLE • J. Bras. Patol. Med. Lab. 57 • 2021 • https://doi.org/10.5935/1676-2444.20210040 copy

Performance evaluation of a Sars-CoV-2 rapid test and two automated immunoassays

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

Introduction: Due to urgency and demand of a response to the Covid-19 pandemic, numerous Sars-CoV-2 immunoassays have been rapidly developed. Objective: This study aimed at assessing the performance of rapid Sars-CoV-2 antibody test in comparison to high-throughput serological assays. Methods: A total of 86 serum samples were evaluated in the three assays: a lateral flow immunoassay - Wondfo Sars-CoV-2 Antibody Test (WRT) - and two chemiluminescence immunoassays: Elecsys Anti-Sars-CoV-2 (ECLIA), and Sars-CoV-2 IgG (CMIA-IgG). Results: The estimated diagnostic sensitivities of serological tests in the evaluation of serum samples from the epidemiological survey were: WRT 59% [95% confidence interval (CI) 43.4%-72.9%], ECLIA 66.7% (51%-79.4%), and CMIA-IgG 61.5% (47.1%-73%). Meanwhile, the estimated diagnostic specificity was for WRT 78.7% (95% CI 65.1%-88%), ECLIA 72.3% (58.2%-83.1%), and CMIA-IgG 76.6% (74%-95.5%). The sensitivity and specificity values were lower than manufacturers’ claimed. Although 16.2% (14/86) of serological results were discordant among the three Sars-CoV-2 serological assays, the degree of agreement by the kappa index was adequate: WRT/CMIA-IgG [0.757 (95% CI 0.615-0.899)], WRT/ECLIA [0.715 (0.565-0.864)], and ECLIA/CMIA-IgG [0.858 (0.748-0.968)]. Conclusion: The serological testing may be a useful diagnostic tool, which reinforces its careful evaluation, and, as well as the correct time to use it.

Key words:
coronavirus infections; serology; antibodies; point of care testing; immunoassay; betacoronavirus

Serum samples	n	WRT (IgM/IgG)			ECLIA (Total Ig)			CMIA (IgG)			CMIA (IgM)
Serum samples	n	P	N	Result	P	N	Result	P	N	Result	P	N	Result
Positive control group	38	Sensitivity value (95% CI)
Initial phase	15	15	0	100% (79.6%-100%)	12	3	80% (54.8%-93%)	13	2	86.7% (62.1%-96.3%)	15	0	100% (79.6%-100%)
Intermediate phase	12	12	0	100% (75.8%-100%)	12	0	100% (75.8%-100%)	12	0	100% (75.8%-100%)	12	0	100% (75.8%-100%)
Late phase	11	11	0	100% (74.1%-100%)	11	0	100% (74.1%-100%)	11	0	100% (74.1%-100%)	11	0	100% (74.1%-100%)
Total		38	0	100% (90.8%-100%)	35	3	92.1% (79.2%-97.3%)	36	2	94.7% (82.7%-98.5%)	38	0	100% (90.8%-100%)
Negative control group	46	Specificity value (95% CI)
Antibodies to other pathologies^* * samples collected before 2019 and reactive to other infectious diseases including: HIV (human immunodeficiency virus), syphilis, HBV (hepatitis B virus), HCV (hepatitis C virus), DENV (dengue virus), YF (yellow fever), MP (Mycoplasma pneumoniae), CHIKV (chikungunya virus);	40	0	40	100% (92.3%-100%)	0	40	97.8% (88.7%-99.6%)	0	40	100% (92.3%-100%)	0	40	100% (92.3%-100%)
Negative^ for serological markers of blood banks.	6	0	6		1	5		0	6		0	6
Total		0	46		1	45		0	46		0	46

Serologic test	Percent agreement	k index	Standard error	95% CI	Observed agreement	Expected agreement	Degree of agreement
WRT/CMIA IgM	100%	1.00	0.000	(1.000-1.000)	1.00	0.50	Very good
WRT/CMIA IgG	97.6%	0.952	0.034	(0.886-1.018)	0.98	0.51	Very good
WRT/ECLIA	95.2%	0.903	0.047	(0.811-0.996)	0.95	0.51	Very good
ECLIA/CMIA IgM	95.2%	0.903	0.047	(0.811-0.996)	0.95	0.51	Very good
ECLIA/CMIA IgG	97.6%	0.951	0.034	(0.885-1.018)	0.98	0.51	Very good

Assay/Result				Number of samples n = 86	Stage of disease (n)
RT- PCR	Wondfo (RT)	Roche (ECLIA)	Abbott (CMIA)	Number of samples n = 86	Stage of disease (n)
Presence of Sars-CoV-2 RNA with symptoms n = 30 (34.9%)	P	P	P	17 (56.7%)	Intermediate (4), and late (13)
	N	N	N	8 (26.7%)	Initial < 7 days (2), and late (6)
	N	P	P	3 (10%)	Late
	P	N	N	1 (3.3%)	Initial (< 7 days)
	N	P	N	1 (3.3%)	Late
Presence of Sars-CoV-2 RNA without symptoms n = 9 (10.4%)	P	P	P	3 (33.3%)	_________
	N	N	N	3 (33.3%)	_________
	N	P	N	1 (11.1%)	_________
	P	P	N	1 (11.1%)	_________
	P	N	P	1 (11.1%)	_________
Absence of Sars-CoV-2 RNA with symptoms n = 12 (14%)	P	P	P	4 (33.3%)	Intermediate (1), and late (3)
	N	N	N	3 (25%)	Late
	N	P	P	3 (25%)	Late
	P	N	N	1(8.3%)	Late
	P	P	N	1 (8.3%)	Late
Absence of Sars-CoV-2 RNA without symptoms n = 35 (40.7%)	P	P	P	4 (11.4%)	_________
	N	N	N	30 (85.7%)	_________
	N	P	N	1 (2.9%)	_________

Serologic test	Number of samples	Percent agreement	k index	Standard error	95% CI	Observed agreement	Expected agreement	Degree of agreement
WRT/CMIA-IgG	86	88.4% (76/86)	0.757	0.072	(0.615-0.899)	0.88	0.52	Good
WRT/ECLIA		86% (74/86)	0.715	0.076	(0.565-0.864)	0.86	0.51	Good
ECLIA/CMIA-IgG		93% (80/86)	0.858	0.056	(0.748-0,968)	0.93	0.51	Very good

Assay	Parameter					Seropositivity	Samples
Assay	Total sensitivity	Total specificity	PPV	NPV	Accuracy	Seropositivity	Samples
WRT (IgM/IgG)	59% (95% CI 43.4%-72.9%)	78.7% (95% CI 65.1%-88%)	69.7%	69.8%	69.8%
ECLIA (Total Ig)	66.7% (95% CI 51%-79.4%)	72.3% (95% CI 58.2%-83.1%)	66.7%	72.3%	69.8%	45.3%	Epidemiological inquiry (n = 86)
CMIA-IgG	61.5% (95% CI 47.1%-73%)	76.6% (95% CI 74%-95.5%)	68.6%	70.6%	69.8%

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[1] CORRESPONDING AUTHOR Márcia Jorge Castejon e-mail: marcia.castejon@ial.sp.gov.br