# Diagnostic Performance of Serological Assays in the Detection of SARS-CoV-2: A Review
###### Abstract  
_Introduction_: The gold-standard method for diagnosis of the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2 or COVID-19) foresees the examination of respiratory tract swabs by real-time reverse-transcription polymerase chain reaction (rRT-PCR). Another group of diagnostic tests, developed to overcome the limitations of RT-PCR, includes the serological assays, which have the purpose of detecting the antibody response to SARS-CoV-2 infection (IgM and IgG titers). The aim of this review was to establish the diagnostic capability of the existing serological tests in the detection of SARS-CoV-2 infection. _Materials and Methods_: Electronic research was conducted in PubMed, Scopus, Science Direct and Cochrane Library, and only 10 articles, testing 10 different types of serological assays, met the inclusion criteria and were consequently submitted to quality assessment and data extraction. Quantitative data about the sensitivity, specificity, positive/negative predictive value and IgM/IgG titer provided by each antibody test were reported in our review. _Results_: Almost all the serological tests used in the included items were recorded to ensure high sensitivity and specificity, identifying the presence of IgM and IgG antibodies against SARS-CoV-2 in patients with certain COVID-19 diagnosis (confirmed by RT-PCR) and in participants with suspected infection (SARS-CoV-2 clinical diagnosis and/or RT-PCR negative subjects). _Conclusions_: Serological tests may represent reliable diagnostic tools in the detection of SARS-CoV-2 infection, and they could be implemented complementary to real-time RT-PCR. Sars-Cov-2; COVID-19; RT-PCR; serological assay; infection +
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sense RNA virus, belongs to the Coronavirus family, as well as the severe acute respiratory syndrome coronavirus 1 (SARS-CoV-1) and Middle East respiratory syndrome coronavirus (MERS-CoV) [4; 5]. Fever, cough expercation, myalgia, fatigue, dyspnea and gastrointestinal symptoms are the most frequent clinical manifestations induced by SARS-CoV-2 [6; 7; 8]. In some cases, the progression of the illness is relatively asymptomatic, while, in other cases, pneumonia, acute respiratory distress syndrome (ARDS), sepsis or septic shock may occur [9; 10]. The main SARS-CoV-2 transmission routes are represented by respiratory droplets (within a long distance of 2 m), generated by infected subjects during coughing and sneezing and by contact with contaminated surfaces [11; 12; 13; 14]. No specific antiviral therapy against SARS-CoV-2 has been introduced yet: treatment protocols include broad-spectrum antiviral drugs (remedesivir, lopinavir, ritonavir, favipiravir), which should be administrated in the early stage of the infection, and antimalarial/autoimmune disease drugs (chloroquine, hydroxychloroquine) [15; 16; 17]. In order to limit the spread of the infection among the population, isolating the infected persons, adequate diagnostic strategies should be implemented. The most commonly used method to detect SARS-CoV-2 foresees the analysis of nasopharyngeal and throat swabs by real-time reverse-transcription polymerase chain reaction (rRT-PCR) test [18; 19; 20]. A complementary diagnostic procedure is represented by the chest computerized tomography (TC) tool, which may allow the detection of the virus in rRT-PCR false-negative cases. Even if real-time RT-PCR plays a crucial role in COVID-19 diagnosis, it presents several limitations: it may not be able to identify the virus in the early stage of the infection, and it requires a long time to obtain the results, which may be influenced by external factors such as sampling operation method and the performance of detection kits and nucleic acid extraction from clinical material [21; 22]. Another group of diagnostic tests used for SARS-CoV-2 identification is that of serological assays.