ABSTRACT
PURPOSE: The precise diagnostic testing is of high importance in fighting the coronavirus pandemic. While nasopharyngeal (NP) swab testing is currently the gold standard, the SARS-CoV-2 virus could be also detected in some other body fluids. In this study, we aimed to compare the SARS-CoV-2 RNA detection results, obtained using saliva samples and NP swab samples, collected from infected patients and healthy volunteers. PATIENTS AND METHODS: A total of 111 individuals were enrolled in this study: 53 healthy volunteers, participating in routine testing and 58 COVID-19 patients. Diagnosis for both groups was confirmed using a set of diagnostic CE-IVD labeled RT-qPCR kits. Most of the saliva samples were collected within 48 hours after the NP swabs were taken. RNA was purified from saliva samples and analyzed using a laboratory-developed kit (Diagnolita). Detection results for both sample types were compared and analyzed in terms of result agreement, Ct variation, and quantity of internal control, as well as population analysis. RESULTS: We found a good concordance between the NP swab and saliva samples. The positive percent agreement was 98.28% (CI 90.76-99.96%) and negative percent agreement was 98.11% (CI 89.93-99.95%). Additionally, we observed a statistically significant (p<0.05) and moderately strong (R = 0.53) correlation between Ct values in saliva and NP swab samples. The saliva collection method is more robust since the Ct variation of internal control ribonuclease P mRNA detection is lower in saliva samples. CONCLUSION: Saliva sample testing is a robust and reliable non-invasive alternative to the NP swab method for SARS-CoV-2 RNA detection, as well as a promising tool for COVID-19 screening.
ABSTRACT
Background and objective: Serologic testing is a useful additional method for the diagnosis of COVID-19. It is also used for population-based seroepidemiological studies. The objective of the study was to determine SARS-CoV-2 seroprevalence in healthcare workers of Kaunas hospitals and to compare two methods for specific SARS-CoV-2 antibody testing. Materials and Methods: A total of 432 healthcare workers in Kaunas hospitals were enrolled in this study. Each participant filled a questionnaire including questions about their demographics, contact with suspected or confirmed COVID-19, acute respiratory symptoms, and whether they contacted their general practitioner, could not come to work, or had to be hospitalized. Capillary blood was used to test for SARS-CoV-2 specific immunoglobulin G (IgG) and immunoglobulin M (IgM) a lateral flow immunoassay. Serum samples were used to test for specific IgG and IgA class immunoglobulins using semiquantitative enzyme-linked immunosorbent assay (ELISA) method. Results: 24.77% of study participants had direct contact with a suspected or confirmed case of COVID-19. A total of 64.81% of studied individuals had at least one symptom representing acute respiratory infection, compatible with COVID-19. Lateral flow immunoassay detected SARS-CoV-2 specific IgG class immunoglobulins in 1.16% of the tested group. Fever, cough, dyspnea, nausea, diarrhea, headache, conjunctivitis, muscle pain, and loss of smell and taste predominated in the anti-SARS-CoV-2 IgG-positive group. Using ELISA, specific IgG were detected in 1.32% of the tested samples. Diarrhea, loss of appetite, and loss of smell and taste sensations were the most predominant symptoms in anti-SARS-CoV-2 IgG-positive group. The positive percent agreement of the two testing methods was 50%, and negative percent agreement was 99.66%. Conclusions: 1.16% of tested healthcare workers of Kaunas hospitals were anti-SARS-CoV-2 IgG-positive. The negative percent agreement of the lateral flow immunoassay and ELISA exceeded 99%.