Evaluation of different platforms for the detection of anti-SARS coronavirus-2 antibodies, Thailand.

BACKGROUND: Antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) help determine previous infection in individuals, regardless of whether they are asymptomatic or symptomatic. The detection of antibodies serves several purposes, including supporting other assays for disease diagnosis, conducting seroepidemiological studies, and evaluating vaccines. Many platforms of immunological methods for anti-SARS-CoV-2 antibody detection and their performance require validation. METHODS: This study evaluated the test performance of three autoanalyzer-based assays (Architect IgG, Vitros IgG, and Vitros total Ig) and one manual ELISA (Wantai total Ig) against a microneutralization (microNT) assay on the detection of SARS-CoV-2 antibodies. Furthermore, an indirect immunofluorescence assay verified the discordant results between the microNT and commercial assays. The test sensitivity, specificity, positive predictive value, and negative predictive value were determined based on four groups of 1005 serum samples: 102 COVID-19 prepandemic sera, 45 anti-SARS-CoV-2 positive sera, 366 sera of people at risk, and 492 sera of citizens returning from countries with a high prevalence of infection. RESULTS: The analyses as a whole showed that the performance of these commercial assays was comparable. Each group was also analysed separately to gain further insight into test performance. The Architect did not detect two positive sera of people at risk (prevalence of infection 0.55%). The other methods correctly identified these two positive sera but yielded varying false-positive results. The group of returning travellers with an infection rate of 28.3% (139 of 492) better differentiated the test performance of individual assays. CONCLUSIONS: High-throughput Architect and Vitros autoanalyzers appear appropriate for working on large sample sizes in countries that can afford the cost. The Wantai ELISA, while requiring more individual time and technical skill, may provide reliable results at a lower cost. The selection of assays will depend on the laboratory facilities and feasibility.

Seroprevalence of anti-SARS-CoV-2 antibodies in Thai adults during the first three epidemic waves.

This study determined the presence of anti-SARS-CoV-2 antibodies in 4964 individuals, comprising 300 coronavirus disease-19 (COVID-19) prepandemic serum samples, 142 COVID-19 patients, 2113 individuals at risk due to their occupations, 1856 individuals at risk due to sharing workplaces or communities with COVID-19 patients, and 553 Thai citizens returning after spending extended periods of time in countries with a high disease prevalence. We recruited participants between May 2020 and May 2021, which spanned the first two epidemic waves and part of the third wave of the COVID-19 outbreaks in Thailand. Their sera were tested in a microneutralization and a chemiluminescence immunoassay for IgG against the N protein. Furthermore, we performed an immunofluorescence assay to resolve discordant results between the two assays. None of the prepandemic sera contained anti-SARS-CoV-2 antibodies, while antibodies developed in 88% (15 of 17) of the COVID-19 patients at 8-14 days and in 94-100% of the patients between 15 and 60 days after disease onset. Neutralizing antibodies persisted for at least 8 months, longer than IgG antibodies. Of the 2113 individuals at risk due to their occupation, none of the health providers, airport officers, or public transport drivers were seropositive, while antibodies were present in 0.44% of entertainment workers. Among the 1856 individuals at risk due to sharing workplaces or communities with COVID-19 patients, seropositivity was present in 1.9, 1.5, and 7.5% of the Bangkok residents during the three epidemic waves, respectively, and in 1.3% of the Chiang Mai people during the first epidemic wave. The antibody prevalence varied between 6.5 and 47.0% in 553 Thai people returning from high-risk countries. This serosurveillance study found a low infection rate of SARS-CoV-2 in Thailand before the emergence of the Delta variant in late May 2021. The findings support the Ministry of Public Health's data, which are based on numbers of patients and contact tracing.

Relationship between body size and severity of dengue hemorrhagic fever among children aged 0-14 years.

A hospital based case-control study was conducted from October 2002 to November 2003 among children aged 0-14 years at Queen Sirikit National Institute of Child Health (Children's Hospital), Bangkok, Thailand. This study focused on body size and severity of dengue hemorrhagic fever (DHF) in children. One hundred five patients diagnosed as having DHF grade III or IV were the cases and 105 diagnosed as having DHF grade I or II were controls. They were matched at a ratio of 1:1 by their gender and age (within 5 years). Normal growth charts were used to differentiate child body size into normal, thin and obese. Data were collected using face to face interviews with caregivers, questionnaires, laboratory and physical examination reports as research tools. Multiple logistic regression analysis revealed that only two variables were related to severity of DHF: obesity (OR = 3.00, 95 % CI = 1.20-7.48) and dengue virus type II (OR = 4.94, 95 % CI = 2.57-9.47), respectively. Other variables were childhood factors: duration of breast-feeding, education, and parity; caregivers factors: age, gender, marital status, education, occupation, family income, knowledge of DHF, antipyretic type, treatment before hospitalization, and duration of fever; environmental factors: history of DHF patients in house, house pattern, time from house to hospital, and residence; and etiological factors: type of infection and history of DHF among children. These factors showed no significant association (p > 0.05). This result can be utilized in a preventive and control program, particularly in more aggressive management of overweight children. Health personnel should continue to provide health education, particularly, signs and symptoms of shock, to the community and private sectors. Government and Non-Government Protective Projects in primary schools (5-9 years children) should be continued in the high risk groups.