# Diagnostic Performance of Serological Assays in the Detection of SARS-CoV-2: A Review
## 3 Results
### Results of Individual Studies  
The data recorded in this review (Tables 3-6) referred to 10 different types of serological tests, which were performed in the included articles in order to establish whether the antibody response can be considered a reliable diagnostic tool for SARS-CoV-2 infection. The VivaDiag COVID-19 IgM/IgG Rapid Test lateral flow immunoassay (LFIA) was used in a sample of 110 patients in the study by [PERSON] et al. [32]: 19 out of 30 cases (63.3%), whose serum samples were taken at a median 7 days after the symptom onset, were positive for both IgM and IgG; five of them were weakly positive; all negative controls were recorded to be negative for both antibodies. The same study also included 50 patients at their first access to the emergency department, who were later tested for COVID-19 by RT-PCR, detecting 38 SARS-CoV-2-positive patients, among whom only seven (18.4%) showed positivity for both IgM and IgG. The sensitivity and specificity of the VivaDiag test were recorded to be 18.4% and 91.7% respectively, results that lead the authors not to recommend its use in the infection diagnostic process. Two of the included items performed the serological test using an iFlash1800 [33] and iFlash3000 [34] fully automated chemiluminescence immunoassay (CLIA) analyzer from Shenzhen YHLO Biotechnology Co., Ltd. (China), respectively. The iFlash1800 CLIA analyzer guaranteed an overall sensitivity of 75% and a specificity of 100% for IgG and 92.2% for IgM. The collected blood samples analyzed thorough this test had a mean duration of 12 days (range 8-17 days) from the onset of symptoms. The iFlash 3000 CLIA analyzer reported, among the cases, 41 IgM/IgG-positive (64.1%), 3 IgM-positive (16.7%) and 5 IgG-positive patients out of 64, with a sensitivity of 48.1% (IgM) and 88.9% (IgG) and a specificity equal to 100% (IgM) and 90.9% (IgG). The duration from first symptoms to the first serological test was, on average, 18 days: both IgM and IgG levels were not high during the first 5 days following symptom onset. [PERSON] et al. [35] used the ALLTEST 2019-nCoV IgM/IgG Rapid Test Cassette (Hangzhou ALLTEST Biotech Co., Ltd. Hangzhou, China) to identify SARS-CoV-2 IgM and IgG in 14 COVID-19-positive patients (six with symptoms and eight without symptoms or with mild symptoms). All the symptomatic subjects showed IgG positivity (6/6), while two of them were IgM-negative (2/6). Three of the asymptomatic patients had positive IgG, but none of them had positive IgM. This research reported the earliest detection of IgM and IgG, on day 5. The sensitivity and specificity of the SARS-CoV-2 rapid IgM/IgG combined antibody test kit developed in the study by [PERSON] et al. [36] were 88.66% and 90.63%, respectively; 256 out of 397 cases and 1 out 128 negative controls were positive for both IgM and IgG. This serological test was performed from day 8 to day 33 after symptoms' appearance. By using a colloidal gold-based immunomodographic (ICG) strip, [PERSON] et al. [37] analyzed 108 blood samples (starting from 7 days after symptom onset), of which 86 were taken from SARS-CoV-2-positive patients (cases) and 22 from subjects with suspected infection (with negative RT-PCR): 55.8% and 54.7% of SARS-CoV-2-positive blood samples showed positivity to IgM and IgG, respectively, while 36.4% and 59.1% of the blood samples taken from patients with suspected infection were positive for IgM and IgG, respectively. In research by [PERSON] et al. [38] the antibodies against this new pathogen were found with an enzyme-linked immunosorbent assay (ELISA): of 66 positive participants, 51 were IgM-positive and 55 were IgG-positive; 21 patients with suspected infection out of 24 were IgM-positive and 17 IgG-positive; negative controls (60) were all negative for IgM and only three were positive for IgG. The detection of the antibodies was conducted from day 4 to day 28 after the beginning of the symptoms, recording an increase in both IgM and IgG rates: from 60% to 63.6% for IgM and from 40% to 90.9% for IgG.