Utility of COVID-19 Serological Tests

Serologic tests can be used to assess the host humoral immune response to the COVID-19 coronavirus. Such tests can play an important role in the fight against the COVID-19 outbreak in addition to viral direct detection methods (nucleic acid amplification or antigen detection tests). They may be used for important clinical and public health applications such as aiding clinical diagnosis, assessing asymptomatic infections/prior exposure, determining potential blood donation for convalescent plasma treatment, and establishing COVID-19 epidemiology in the general population. Furthermore, they may provide important information to determine protective immunity on an individual basis or in a community and help establish informed strategies to re-open our society. However, current challenges in test performance (accuracy, reliability, information density) have limited their value in these very important applications.

Current Challenges in COVID-19 Serological Tests

Creator: Yulia Reznikov | Credit: Getty Images Copyright: Yulia Reznikov

Due to the high infectiousness and serious lethality of the COVID-19 coronavirus, it is critical that serological test results are highly accurate, especially if it is to be used to evaluate whether an individual may have potential immunity. The positive predictive value (PPV) and negative predictive value (NPV) of such tests are determined by prevalence in the population (pre-test probability) and the sensitivity and specificity of the test and can have significant impact on the overall value of such tests. For example, in a population where COVID-19 prevalence is 5%, a test with 90% sensitivity and 95% specificity will result in a positive predictive value of only 49%; if the prevalence is 2%, positive predictive value will decrease even further to 27%. To put it another way, using such tests there is low probability or confidence of those testing positive to truly have antibodies against COVID-19. In addition, currently most serological tests are not able to provide quantitative information (i.e., antibody titers), and some tests may exhibit cross-reactivity with other coronaviruses, e.g., the common cold coronaviruses, which can also contribute to false-positive test results. (Reference: CDC Interim Guidelines for COVID-19 Antibody Testing.)

Building Partnership and Developing New COVID-19 Serological Tests

Velox is highly motivated to leverage our expertise in diagnostic technology to help develop new tools in the fight against the COVID-19 outbreak. We are working closely with our partners to develop a high-resolution, high-throughput serological testing service and future product for COVID-19 countermeasure. The solution we are working on can provide quantitative, high resolution, high information density, and highly accurate results. In comparison to the low positive predictive values with many current serological tests, our goal is to achieve very high positive predictive value even if population prevalence is low (e.g., PPV = 95% with prevalence = 2%). As such, our test could offer real value in assessing whether an individual has developed antibodies against COVID-19  due to known infection or asymptomatic infection. In addition to detecting and quantifying antibodies specific to SARS-CoV-2 (COVID-19), our solution leverages a full respiratory viral panel which will include other coronavirus families, common influenza strains, and etc. The high information density of our solution can therefore provide much more complete immune profiling, which could be especially important if the COVID-19 outbreak persists and co-mingles with the flu season later on.

Current status and our near-term plan

We will soon be launching a high-throughput CLIA testing service and will offer contract testing services for urgent RUO studies such as clinical research (diagnosis/prognosis), epidemiological studies, new vaccine/therapy development (testing antibody levels before and after treatment). Once launched, we also plan to apply for FDA Emergency Use Authorization (EUA).

In addition to establishing a contract testing service, we are also working with our partners to develop (i) an integrated, portable analyzer that can be available to other groups/labs in the near future; and (ii) a high-throughput testing platform that can be deployed in labs for high volume testing. And given that our solution provides quantitative, high resolution, high information density data, we also plan to include a cloud-based big data analysis feature to our product. As there is high heterogeneity in the immune response to COVID-19 due to various demographic and clinical factors, we believe the big data feature can help uncover unique insights, further our understanding of immune response and protection, and provide community-based epidemiological information for the safe-reopening of our society.