Serological follow up of positive SARS-CoV-2 cases.

OBJECTIVE: To describe the humoral response in a cohort with mild and asymptomatic SARS-CoV-2 infection previ-ously identified in a community-based serological survey. MATERIALS AND METHODS: This study was an observational follow up of 193 subjects previously identified with positive anti-SARS-CoV-2 antibodies invited for a second test 112 days after the first sampling. All completed a standardized electronic questionnaire. IgM/IgG antibodies were determined using a qualitative IgM/IgG chemiluminescent immunoassay. RESULTS: Among the 193 eligible subjects, a total of 174 (90%) attended the follow-up visit, and their serum samples were tested. Of the samples, 171 (98.3%) were still positive, and 3 (1.7%) were negative. Also, the cut-off index (COI) value of the immunoassay significantly increased from the first to the second test (P <0.001). CONCLUSIONS: Our findings support a sustained humoral response in individuals with mild and asymptomatic SARS-CoV-2 infection up to 112 days after a positive serologic baseline test, accompanied by increasing antibody titers.

Acute cerebrovascular events in severe and nonsevere COVID-19 patients: a systematic review and meta-analysis.

The degree to which COVID-19 severity influences the development of acute cerebrovascular events (ACVE) is unknown. Therefore, we aimed to describe the prevalence and risk of ACVE in patients with severe and nonsevere COVID-19. We systematically reviewed MEDLINE, EMBASE, Web of Science, and Scopus and identified observational and interventional studies of patients with COVID-19 allocated by respiratory severity that reported ACVE development. Case reports/series were excluded. The main outcome assessed was the pooled rate of ACVE in patients with severe and nonsevere COVID-19. To determine the risk of ACVE development by COVID-19 severity, a meta-analysis was performed. PROSPERO registration number: CRD42020178905. About 19 of 5758 identified studies were analyzed. From 11,886 COVID-19 patients analyzed, 421 had at least one ACVE [3.6%, 95% confidence interval (CI) 2.904-4.179]. Severe COVID-19 increased the risk of ACVE (odds ratio 1.96, 95% CI 1.22-3.15; P = 0.005; I 2 = 64%), specifically hemorrhagic stroke (4.12, 2.0-8.53; P = 0.001; I 2 = 0%). There was no difference in the risk of developing ischemic stroke between patients with severe and nonsevere COVID-19 (1.53, 0.87-2.7; P = 0.14; I 2 = 52%). From the patients who developed any ACVE, those with severe COVID-19 had a greater mortality risk than those with nonsevere COVID-19 (3.85, 1.08-13.70; P = 0.04; I 2 = 0%). The main limitations of our study were the heterogeneity found in the main meta-analysis studies and in their reported definition for COVID-19 severity. In conclusion, our findings provide evidence that COVID-19 respiratory severity could lead to ACVE development that increases mortality. The effect of COVID-19 management in ACVE needs to be evaluated.

Prevalence and associated characteristics of anti-SARS-CoV-2 antibodies in Mexico 5 months after pandemic arrival.

BACKGROUND: Seroprevalence of anti-SARS-CoV-2 antibodies is now available in several world regions to better estimate transmission dynamics. However, to date, there is no epidemiological data regarding anti-SARS-CoV-2 prevalence in Mexico. Therefore, we aimed to determine the prevalence of anti-SARS-CoV-2 antibodies and define the clinical and demographic characteristics associated with seroprevalence. METHODS: We conducted a cross-sectional serological survey in Ciudad Guadalupe, NL, Mexico. City government employees voluntarily participated during July 2020. Demographic and clinical characteristics were collected at the time of blood sampling to analyze the associated characteristics. IgM/IgG antibodies were determined using a qualitative chemiluminescent immunoassay. Descriptive statistics were used for categorical and continuous variables. Statistical significance was tested using the Chi-squared test, Student's t-test and the Mann-Whitney. Logistic regression models and the odds ratios (adjusted and unadjusted) were used to estimate the association of demographic and clinical characteristics. RESULTS: Of the 3,268 participants included, 193 (5.9%, 95% CI 5.1-6.8) tested positive for IgM/IgG against SARS-CoV-2. Sex, city of residence, and comorbidities did not show any association with having IgM/IgG antibodies. A total of 114 out of 193 (59.1%) subjects with a positive test were asymptomatic, and the odds of being positive were higher in those who reported symptoms of COVID-19 in the previous four weeks to the survey (OR 4.1, 95% CI 2.9-5.5). CONCLUSIONS: There is a low rate of SARS-CoV-2 infection among government employees that have continuously been working during the pandemic. Six in ten infections were asymptomatic, and seroprevalence is low and still far from herd immunity. Epidemiological surveillance and preventive measures should be mandatory.

Scoping review of COVID-19-related systematic reviews and meta-analyses: can we really have confidence in their results?

AIM: The aim of this study was to systematically appraise the quality of a sample of COVID-19-related systematic reviews (SRs) and discuss internal validity threats affecting the COVID-19 body of evidence. DESIGN: We conducted a scoping review of the literature. SRs with or without meta-analysis (MA) that evaluated clinical data, outcomes or treatments for patients with COVID-19 were included. MAIN OUTCOME MEASURES: We extracted quality characteristics guided by A Measurement Tool to Assess Systematic Reviews-2 to calculate a qualitative score. Complementary evaluation of the most prominent published limitations affecting the COVID-19 body of evidence was performed. RESULTS: A total of 63 SRs were included. The majority were judged as a critically low methodological quality. Most of the studies were not guided by a pre-established protocol (39, 62%). More than half (39, 62%) failed to address risk of bias when interpreting their results. A comprehensive literature search strategy was reported in most SRs (54, 86%). Appropriate use of statistical methods was evident in nearly all SRs with MAs (39, 95%). Only 16 (33%) studies recognised heterogeneity in the definition of severe COVID-19 as a limitation of the study, and 15 (24%) recognised repeated patient populations as a limitation. CONCLUSION: The methodological and reporting quality of current COVID-19 SR is far from optimal. In addition, most of the current SRs fail to address relevant threats to their internal validity, including repeated patients and heterogeneity in the definition of severe COVID-19. Adherence to proper study design and peer-review practices must remain to mitigate current limitations.