Diagnostic Accuracy of the SARS-CoV-2 IgG/IgM Rapid Test Cassette (Healgen®) in the Management of Suspected Patients with Coronavirus Disease 2019 (COVID-19)

Abstract

Introduction: COVID-19 infection is the most rapidly growing pandemic in modern time. Its diagnosis in the hospital setting was limited by the lack of adequate laboratory diagnostic tools available in the Philippines. When the community outbreak was declared, only two national reference laboratories approved by WHO were capable of performing the reference standard test RT-PCR for the diagnosis of Covid-19 disease. However, due to the slow turn around time of processing of RT-PCR samples, lasting 6-10 days prior to release of result, we were crucially in need of a rapid test for diagnostic investigation. This highlights the urgent need to have widespread, reliable diagnostic test.Objective: To determine the diagnostic accuracy of SARS-COV-2 IgG/IgM Rapid Test Cassette (Healgen®) in the management of suspected patients with coronavirus disease 2019 (COVID-19) in Cardinal Santos Medical Center.Methods: Serum blood samples from 164 COVID suspects were collected and subjected to the IgG/IgM rapid antibody test. The results were correlated with the days of illness and their SARS-Cov-2 RT-PCR test result. Utilizing the gold standard SARS-Cov-2 RT-PCR, sensitivity, specificity, positive and negative predictive values, likelihood ratios and overall accuracy rates were computed. Antibody detection rates were also computed from onset of patient’s illness among the confirmed sample population.Results: The sensitivity of the rapid antibody test for symptomatic adult, Covid 19 positive patients seen at Cardinal Santos Medical Center, Philippines from March to May 2020 was 84% (IgM) and 76% (IgG). When both IgM and IgG are positive, the sensitivity and specificity are similar at 80%. The positive likelihood ratio if both antibodies are positive is 4. The specificity for asymptomatic individuals was 98% (IgM) and 96% (IgG). Likewise, the negative predictive values are 96% and 94% for IgM and IgG. Overall, the sensitivity and specificity of IgM are 82% and 86% respectively. IgM antibodies were detected early in the first week of illness in 54% of the hospitalized confirmed patients. Detection of IgG on the other hand was highest during the second and third weeks of illness. Total or both antibodies were detectable up to 4 weeks from illness onset. IgM antibodies were detected earlier than IgG. IgM positivity rate was higher than IgG by the second week illness (IgM 100% vs IgG 93%), both antibodies have the same positivity rates up to the fourth week of observation.Conclusion: The Healgen® antibody has good performance rates, it can be applied clinically for the diagnosis of Covid 19 disease in comparison with the standard RT-PCR . Results should be interpreted according to the patients’ duration of illness. It also has the potential for use to determine asymptomatic infection among those at risk.Funding Statement: None to declare.Declaration of Interests: There was no conflict of interest in conducting the study.Ethics Approval Statement: This study was approved by the ethics board at the Cardinal Santos Medical Center.