Seroprevalence of SARS-CoV-2 in unselected surgical patients: An update from an unicentric regional study

After a mitigation in the Summer season [1], the COVID-19 pandemic is progressing quickly in Europe. In Italy the COVID-19 total number of registered cases at the end of 2020 has reached over 2 million units with about 75,000 confirmed deaths, causing an excessive load to the national healthcare system [2–4]. Our region, Sardinia, showed an important increase in SARS-CoV-2 cases: the total number has reached quickly over 30,000 cases and 750 deaths attributable to COVID-19 [4], forcing local authorities to reorganize the hospitals, with a sharp reduction in ordinary surgical activities. In our Department of General and Endocrine Surgery of University Hospital of Cagliari, a non-dedicated COVID-19 hospital, activity was reduced from the first week of November, allowing only emergencies, oncological and not postponable procedures. Similarly as we have done in our previous work [5], we have herein analysed the patients admitted to our Department that underwent testing for SARS-CoV-2 Antibodies (Ab) to evaluate the difference of seroprevalence between Spring and Fall seasons, and to estimate the prevalence of SARS-CoV-2 infection in the setting of a non-dedicated COVID-19 hospital in a mild-incidence area. Between 1St September – 10Th December 2020, 121 patients were admitted to our Department for elective surgery, performed serologic tests for SARS-CoV-2 during the prehospitalization check, and were included in this study. All patients were asked for SARS-CoV-2 risk factors, including symptoms during the last 2 weeks and close contact with confirmed cases. A Chemiluminescent-Analytical-System (CLIA) for the detection of both IgM and IgG antibodies against SARS-Cov-2 Spike protein and Nprotein on Maglumi platform (Snibe, Shenzhen, China) was employed (IgM cut-off 1.0 AU/mL, IgG cut-off 1.1 AU/mL). The main indication for elective surgery was thyroid and parathyroid disease in 57 (47.1%) cases, including thyroid malignancy, goiter and hyperparathyroidism. Surgery for breast, colorectal, skin cancer, and abdominal wall disease was also performed. All patients underwent a chest X-ray. No suspicious radiological signs were detected. All 121 patients underwent at least one nasopharyngeal swab before admission. RT-PCR was performed by GENESIG primerxdesign ® LTD, Chandels’ Ford UK on CFX96 BioRad, (Cycle Threshold from 20 to 40). Forty-one (33.9%) patients were males and 80 (66.1%) females, with a mean age of 58.6 ± 16.6 years. At serology, 8 (6.6%) patients tested positive for only SARS-CoV-2 specific IgM, and 5 (4.1%) for only SARS-CoV-2 specific IgG (Table 1).