Evaluation of Serological SARS-CoV-2 Lateral Flow Assays for Rapid Point-of-Care Testing

Abstract

Rapid point-of-care tests (POCTs) for detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific antibodies vary in performance. A critical need exists to perform head-to-head comparisons of these assays. The performances of 15 different lateral flow POCTs for the detection of SARS-CoV-2-specific antibodies were compared on a well-characterized set of 100 samples. Of these, 40 samples from known SARS-CoV-2-infected, convalescent individuals (collected an average of 45 days after symptom onset) were used to assess sensitivity. Sixty samples from the prepandemic era (negative control) that were known to represent infections with other respiratory viruses (rhinoviruses A, B, and C and/or coronavirus 229E, HKU1, and NL63 OC43) were used to assess specificity. The timing of seroconversion was assessed using five lateral flow assays (LFAs) and a panel of 272 longitudinal samples from 47 patients for whom the time since symptom onset was known. Among the assays that were evaluated, the sensitivity and specificity for any reactive band ranged from 55% to 97% and from 78% to 100%, respectively. Assessing the performance of the IgM and the IgG bands alone, sensitivity and specificity ranged from 0% to 88% and 80% to 100% for IgM and from 25% to 95% and 90% to 100% for IgG, respectively. Longitudinal testing revealed that the median times after symptom onset to a positive result were 7 days (interquartile range [IQR], 5.4 to 9.8) for IgM and 8.2 days (IQR, 6.3 to 11.3) for IgG. The testing performances differed widely among LFAs, with greatest amount of variation related to the sensitivity of the assays. The IgM band was the band most likely to misclassify prepandemic samples. The appearances of IgM and IgG bands occurred almost simultaneously.

Keywords: SARS-CoV-2 serology; cross-reactivity; performance; point-of-care test.

FIG 1

Analytical sensitivity and specificity toward IgM and IgG for the evaluated SARS-CoV-2 antibody-based assays. The boxes represent the lower and upper 95% confidence intervals (95% binomial exact CI), and the lines inside the boxes indicate the values determined for each assay.

FIG 2

Comparison of 15 evaluated LFA and two ELISA-based assay results obtained by testing the designated negative or positive plasma sample. (a) Results obtained from evaluating prepandemic (negative) and convalescent (positive) plasma. Any detection of IgM or IgG or both is shown as a positive result (blue), whereas lack of detection is shown as a negative result (yellow).Those marked in gray indicate an invalid result, while those marked in white represent missing data for comparison. (b) Agreement (IgM or IgG) between each LFA and ELISAs (in italics). The values shown represent the kappa agreement values, which are interpreted as representing no agreement (<0), slight agreement (0.00 to 0.20), fair agreement (0.021 to 0.40), moderate agreement (0.41 to 0.060), substantial agreement (0.61 to 0.80), almost perfect agreement (0.81 to 1.00), or perfect agreement (1.00).

FIG 3

Longitudinal evaluation of analytical performance for four SARS-CoV-2 antibody-based LFAs and two ELISAs. The boxes represent the lower and upper 95% confidence intervals (95% binomial exact CI), and the line inside each box indicates the value determined for each assay at each indicated time range.