Test performance evaluation of SARS-CoV-2 serological assays
Authors: Whitman Jeffrey D. , Hiatt Joseph , Mowery Cody T. , Shy Brian R. , Yu Ruby , Yamamoto Tori N. , Rathore Ujjwal , Goldgof Gregory M. , Whitty Caroline , Woo Jonathan M. , Gallman Antonia E. , Miller Tyler E. , Levine Andrew G. , Nguyen David N. , Bapat Sagar P. , Balcerek Joanna , Bylsma Sophia A. , Lyons Ana M. , Li Stacy , Wong Allison Wai-yi , Gillis-Buck Eva Mae , Steinhart Zachary B. , Lee Youjin , Apathy Ryan , Lipke Mitchell J. , Smith Jennifer Anne , Zheng Tina , Boothby Ian C. , Isaza Erin , Chan Jackie , Acenas Dante D. , Lee Jinwoo , Macrae Trisha A. , Kyaw Than S. , Wu David , Ng Dianna L. , Gu Wei , York Vanessa A. , Eskandarian Haig Alexander , Callaway Perri C. , Warrier Lakshmi , Moreno Mary E. , Levan Justine , Torres Leonel , Farrington Lila A. , Loudermilk Rita , Koshal Kanishka , Zorn Kelsey C. , Garcia-Beltran Wilfredo F. , Yang Diane , Astudillo Michael G. , Bernstein Bradley E. , Gelfand Jeffrey A. , Ryan Edward T. , Charles Richelle C. , Iafrate A. John , Lennerz Jochen K. , Miller Steve , Chiu Charles Y. , Stramer Susan L. , Wilson Michael R. , Manglik Aashish , Ye Chun Jimmie , Krogan Nevan J. , Anderson Mark S. , Cyster Jason G. , Ernst Joel D. , Wu Alan H. B. , Lynch Kara L. , Bern Caryn , Hsu Patrick D. , Marson Alexander 
Published: April 2020

Background

Serological tests are crucial tools for assessments of SARS-CoV-2 exposure, infection and potential immunity. Their appropriate use and interpretation require accurate assay performance data.

Method

We conducted an evaluation of 10 lateral flow assays (LFAs) and two ELISAs to detect anti-SARS-CoV-2 antibodies. The specimen set comprised 128 plasma or serum samples from 79 symptomatic SARS-CoV-2 RT-PCR-positive individuals; 108 pre-COVID-19 negative controls; and 52 recent samples from individuals who underwent respiratory viral testing but were not diagnosed with Coronavirus Disease 2019 (COVID-19). Samples were blinded and LFA results were interpreted by two independent readers, using a standardized intensity scoring system.

Results

Among specimens from SARS-CoV-2 RT-PCR-positive individuals, the percent seropositive increased with time interval, peaking at 81.8-100.0% in samples taken >20 days after symptom onset. Test specificity ranged from 84.3-100.0% in pre-COVID-19 specimens. Specificity was higher when weak LFA bands were considered negative, but this decreased sensitivity. IgM detection was more variable than IgG, and detection was highest when IgM and IgG results were combined. Agreement between ELISAs and LFAs ranged from 75.7-94.8%. No consistent cross-reactivity was observed.

Conclusion

Our evaluation showed heterogeneous assay performance. Reader training is key to reliable LFA performance, and can be tailored for survey goals. Informed use of serology will require evaluations covering the full spectrum of SARS-CoV-2 infections, from asymptomatic and mild infection to severe disease, and later convalescence. Well-designed studies to elucidate the mechanisms and serological correlates of protective immunity will be crucial to guide rational clinical and public health policies.