Evaluation of Performance Characteristics of the StandardTM Q IgM/IgG and the Wantai SARS-CoV-2 Ab Rapid Tests in Tanzania

Abstract

Background: Rapid diagnostic tests (RDTs) have played a critical role in the detection and monitoring of severe acute
respiratory syndrome coronavirus 2 (SARS-CoV-2) infections globally. A number of RDTs are currently available, and their
accuracy is dependent on several factors that include disease stage, circulating virus variants at the particular time, and
the population being tested. This study aimed to evaluate the performance characteristics of two RDTs, the StandardTM
Q IgM/IgG and the Wantai SARS-CoV-2 Ab Rapid Test, for the detection of SARS-CoV-2 antibodies in a Tanzanian
population.
Methods: Plasma samples from a total of 80 individuals stored at the National Institute for Medical Research-Mbeya
Medical Research Centre (NIMR-MMRC) biobank were tested. Of these, 37 (46.3%) were confirmed to have been
exposed to the SARS-CoV-2 virus through either RT-PCR or Ag rapid tests from ongoing COVID-19 studies. The remaining
43 (53.6%) serving as negative controls, were stored samples from SARS-CoV-2 unexposed individuals obtained from
an HIV cohort enrolled between 2014 and 2017. All the samples were tested using both the StandardTM Q IgM/IgG
and the Wantai SARS-CoV-2 Ab Rapid Test. The sensitivity, specificity, and other performance characteristics of each
test were determined.
Results: The StandardTM Q IgM/IgG test demonstrated a higher sensitivity of 100% (95% CI: 74–100%) for patients with
acute COVID-19 (less than ten days since onset of symptoms). The Wantai SARS-CoV-2 Ab rapid test had a sensitivity
of 75% (95% CI: 43–95%). Both tests revealed a specificity of 100% (95% CI: 74–100%). For patients with more
than 30 days since the onset of symptoms, the StandardTM Q IgM/IgG test showed a sensitivity of 96% (95% CI: 80-
100%), while the Wantai total Ab assay had a sensitivity of 92% (95% CI: 74-99%), and again both test kits revealed
a specificity of 100% (95% CI: 74-100%).
Conclusion: The StandardTM Q IgM/IgG Rapid Diagnostic Test is recommended to be used as the primary test for
COVID-19 survey screening purposes due to its higher sensitivity, while the Wantai total Ab RDT is recommended to be
regarded as the second option.