Benefits of SARS-CoV-2 Serology Testing
Serology testing can help enrich epidemiological data through sero-surveillance to inform policymaking at different levels, especially when asymptomatic cases seem to be high. While some preliminary studies estimated the proportion of asymptomatic cases at 17.9%, others go as high as 40% [32,33]. Although serology tests cannot replace RNA tests in hospital settings, they may provide additional information to support decision making on patient clinical diagnosis [34]. Hence, conducting serology tests in the clinical setting, when the index of suspicion is high, but SARS-CoV-2 cannot be detected, represents an opportunity to determine if a patient had been infected, providing relevant data that can help complete datasets and enhance preparedness. Finally,
implementation of systematic serology testing and sero-surveillance could also provide an alternative method to less accessible and affordable lab RNA testing [35]. To summarize, evidence suggests that serology testing can be used as one of the tools to control virus transmission, prevent community spread, and meet public health and community needs and demands.
Serology testing might also be beneficial for research purposes, especially under scenarios where the virus is still new and less prone to mutations and genetic diversification. The use of serological tests to assist the development of effective treatments and/or vaccines is prescribed in this context [36], as so is research to identify the role of neutralizing antibodies [37,38]
.Challenges of SARS-CoV-2 Serology Testing
Although WHO has acknowledged the importance of serology testing for epidemiological surveillance and research purposes, it provides limited guidance and support on implementation, and lacks emphasis on the value of other possible benefits. The existing WHO interim guidelines on the use of POC immunodiagnostic tests recommends molecular testing as a gold standard [37], and in the latest interim guideline indicates serology testing as complementary in specific cases [39].
At the regional level, the European Commission has acknowledged the overall utility of serology testing [40], releasing its guidelines on SARS-CoV-2 testing in April 2020 [41]. That same month, the ECDC published its Strategies for the Surveillance of COVID-19 [42]. However, neither of these documents set a clear plan for rolling out serology testing across the region. Meanwhile, some European countries have independently implemented serology testing strategies, while others are still lagging [9,43] (see Supplementary Material 1). A list of sero-epidemiological studies conducted in the region can also be found on the ECDC’s website [44]. The fragmented initiatives across the region might result in the loss of opportunities to gather critical information in an organized manner at a crucial time. Furthermore, in absence of comprehensive guidance, access to quality testing might be hindered due to insufficient supply and availability, and, in some cases, limited health systems capacity (effective infrastructure and a trained health workforce) [45].
Policy Recommendations
The eight policy recommendations offered in this paper focus on two main themes: the first four recommendation address the role and value of serology testing to contain and understand the SARS-CoV-2 pandemic, and the last four address issues around health system strengthening. As shown in Table 1, serology testing might be a valuable resource and should be considered as part of a larger comprehensive pandemic preparedness and mitigation strategy. Currently serology testing is primarily recommended for sero-surveillance and research purposes; however, this study found the need to define targeted pathways and a framework for ultimate introduction of serology testing to complement the existing strategies along with new scientific and clinical data as it becomes available. Active promotion of well-designed projects should facilitate this goal. Moreover, evidence suggests - and this paper recommends - to prioritize by geographic hotspots and to consider serology testing as part of national containment strategies to jumpstart the economy for full control of epidemics.
Table 1. Recommendations on the role and value of serology testing to contain and understand SARS-CoV-2 pandemic