Korea Seroprevalence Study of Monitoring of SARS-COV-2 Antibody Retention and Transmission (K-SEROSMART): findings from national representative sample.

OBJECTIVES: We estimated the population prevalence of antibodies to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), including unreported infections, through a Korea Seroprevalence Study of Monitoring of SARS-CoV-2 Antibody Retention and Transmission (K-SEROSMART) in 258 communities throughout Korea. METHODS: In August 2022, a survey was conducted among 10,000 household members aged 5 years and older, in households selected through two stage probability random sampling. During face-to-face household interviews, participants self-reported their health status, COVID-19 diagnosis and vaccination history, and general characteristics. Subsequently, participants visited a community health center or medical clinic for blood sampling. Blood samples were analyzed for the presence of antibodies to spike proteins (anti-S) and antibodies to nucleocapsid proteins (anti-N) SARS-CoV-2 proteins using an electrochemiluminescence immunoassay. To estimate the population prevalence, the PROC SURVEYMEANS statistical procedure was employed, with weighting to reflect demographic data from July 2022. RESULTS: In total, 9,945 individuals from 5,041 households were surveyed across 258 communities, representing all basic local governments in Korea. The overall population-adjusted prevalence rates of anti-S and anti-N were 97.6% and 57.1%, respectively. Since the Korea Disease Control and Prevention Agency has reported a cumulative incidence of confirmed cases of 37.8% through July 31, 2022, the proportion of unreported infections among all COVID-19 infection was suggested to be 33.9%. CONCLUSIONS: The K-SEROSMART represents the first nationwide, community-based seroepidemiologic survey of COVID-19, confirming that most individuals possess antibodies to SARS-CoV-2 and that a significant number of unreported cases existed. Furthermore, this study lays the foundation for a surveillance system to continuously monitor transmission at the community level and the response to COVID-19.

Seroprevalence of SARS-CoV-2 antibodies during the third wave of COVID-19 in the Seoul metropolitan area of Korea.

OBJECTIVES: After the third wave of coronavirus disease 2019 (COVID-19), by mid-February 2021, approximately 0.16% of the Korean population was confirmed positive, which appeared to be among the lowest rates worldwide at that time. However, asymptomatic transmission is challenging for COVID-19 surveillance. Therefore, a community-based serosurvey of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection was conducted to understand the effectiveness of Korea's strong containment strategy. METHODS: We collected 5,002 residual sera samples from January 30 to March 3, 2021, from 265 medical facilities in Seoul, 346 in Gyeonggi Province, and 57 in Incheon. Sixty samples from tertiary institutions were excluded. We defined the sub-regions according to the addresses of the medical facilities where the specimens were collected. Elecsys Anti-SARS-CoV-2 was used for screening, and positivity was confirmed using the SARS-CoV-2 sVNT Kit. Prevalence was estimated using sampling weights and the Wilson score interval for a binomial proportion with a 95% confidence interval. RESULTS: Among the 4,942 specimens, 32 and 25 tested positive for COVID-19 in the screening and confirmatory tests, respectively. The overall crude prevalence of SARS-CoV-2 antibodies was 0.51%. The population-adjusted overall prevalence was 0.55% in women and 0.38% in men. The region-specific estimation was 0.67% and 0.30% in Gyeonggi Province and Seoul, respectively. No positive cases were detected in Incheon. CONCLUSIONS: The proportion of undetected cases in Korea remained low as of early 2021. Therefore, an infection control strategy with exhaustive tracing and widespread pre-emptive testing appears to be effective in containing community spread of COVID-19.

Hepatitis E Virus (HEV) seroprevalence in the general population of the Republic of Korea in 2007-2009: a nationwide cross-sectional study.

BACKGROUND: Hepatitis E virus (HEV) is an emerging pathogen associated with endemic and acute viral hepatitis. In this study, we investigate the HEV seroprevalence and putative risk factors by a nationwide cross-sectional study in the Republic of Korea. METHODS: The prevalence of anti-HEV antibody was investigated in 2,450 serum samples collected in fourth Korea National Health and Nutrition Examination Survey. In addition, epidemiological information on possible risk factors including gender, age, education, occupation, and residence location for exposure to HEV was obtained. RESULTS: The frequency of anti-EIA reactive sample was 5.9% (144/2450). The individuals in groups with male, older age, low education level and living in rural or coastal regions had high seroprevalence estimates (P ≤ 0.001). In addition, seroprevalence was significantly higher among individuals with self-identified skilled agricultural, forestry, and fishery workers (31.3%, P < 0.001). CONCLUSIONS: This study provides valuable data that could be used to investigate associations of HEV seroprevalence and putative risk factors by a nationwide cross-sectional study. The high HEV seroprevalence of skilled agricultural, forestry, and fishery workers and individuals lived in coastal and rural area indicated that zoonotic transmission is an important risk factor for HEV infection in the republic of Korea. Further studies that include detailed and continuous nationwide surveys are required to identify unrecognized risk factors and to monitor the HEV infection prevalence.

Performance evaluation of the OraQuick hepatitis C virus rapid antibody test.

BACKGROUND: A reliable rapid assay for hepatitis C virus (HCV) may be helpful in various clinical settings. We evaluated the performance of the OraQuick HCV Rapid Antibody Test (OraSure Technologies Inc., Bethlehem, PA, USA). METHODS: Clinical sensitivity and specificity were evaluated with oral fluids and sera from 137 patients diagnosed with hepatitis C and 300 healthy blood donors in a multi-center collaborative study. The stored sera of 200 proven HCV-infected patients and 200 healthy subjects were also evaluated. Analytical sensitivity was estimated with 4 commercial seroconversion panels and 7 Korean reference panels. The performance of 4 laboratory-based tests (3 chemiluminescence assays and 1 enzyme immunoassay) and 4 rapid test kits was compared. We also assessed the interference due to bilirubin, hemoglobin, lipid, rheumatoid factor, multipara, and several viral infections. RESULTS: The clinical sensitivity and specificity of the OraQuick HCV test using oral fluid were 97.8% (95% confidence interval [CI], 93.2-99.4%) and 100% (95% CI, 98.4-100%), respectively. The clinical sensitivity using serum samples was 100%. Using the 4 seroconversion panels, the OraQuick HCV test showed results comparable to those of the laboratory-based assays; its analytical sensitivity was higher than that of the other rapid test kits. There was no cross-reactivity with common interfering factors. CONCLUSIONS: The clinical performance of the OraQuick HCV Test is comparable to that of laboratory-based tests with both serum and oral fluid. This supports the supplementary use of rapid HCV testing using oral fluid in various medical and non-medical settings.

[Effectiveness of sodium fluoride as a glycolysis inhibitor on blood glucose measurement: comparison of blood glucose using specimens from the Korea National Health and Nutrition Examination survey].

BACKGROUND: Accurate measurement of blood glucose concentrations is essential for defining diabetes, and the minimization of ex vivo glycolysis has been recommended. Recent guidelines advocate two kinds of methods for sample collection and processing: either the sodium fluoride (NaF) method or immediate refrigeration using a serum separation tube (SST). We investigated the difference between the two methods in measuring subsequent glucose concentrations using blood specimens from participants recruited for the fourth Korean National Health and Nutrition Examination Survey. METHODS: Paired venous blood samples were collected in an SST and a NaF tube from 1,103 men and women. SST serum was separated within 30 min, including standing for 15 min, and then refrigerated. The NaF samples were refrigerated, but not separated until immediately before analysis. We compared the blood glucose concentrations between the SST (SST glucose) and NaF (NaF glucose) methods. RESULTS: The mean SST glucose was significantly higher than NaF glucose (99.0 mg/dL vs 96.5 mg/dL, P<0.05). NaF glucose showed a negative mean bias of 2.6 mg/dL vs SST glucose but showed high correlation (R=0.9899). There was no significant correlation between the bias of blood glucose concentrations by two methods and the storage time of NaF glucose. CONCLUSIONS: The negative bias associated with the use of NaF tubes may significantly affect the prevalence of diabetes. Serum separation and refrigeration within 30 min after venous sampling is recommended over NaF method, not only to minimize the preanalytical impact on detecting diabetes but also to reduce sample volume and number of tubes.

[Survey results of medical insurance reimbursement system for independent medical laboratories in Korea].

BACKGROUND: A questionnaire survey was performed to perceive the problem of the current medical insurance reimbursement system for laboratory tests referred to independent medical laboratories; then, we intended to find a way to improve the reimbursement system. METHODS: Questionnaires were distributed to 220 independent medical laboratories and 700 laboratory physicians from July through October 2005. Frequency analysis was used to analyse the replies from 109 respondents to 25 questionnaire items regarding the current medical insurance reimbursement system for referral tests, problems with the system, and suggestions for the improvement of the system. RESULTS: Among the 109 respondents to this survey, 49 (45.8%) considered the current reimbursement system to be unsatisfactory, while only 16 (15.0%) answered satisfactory. The problem was that the referral clinics-not the laboratories that performed the tests--would first receive their reimbursement for the laboratory tests from Health Insurance Review Agency (HIRA) and then give a portion of the laboratory test fees to the independent medical laboratories after the deduction of administrative fees. They (62.5% of the respondents) would prefer a separated reimbursement system by which the referral clinic-as well as the independent medical laboratory-would receive their reimbursement directly from HIRA through an Electronic Data Interchange (EDI) system. In this new system, 34% of the respondents expected the quality of the laboratory tests to be improved; however, 41.6% answered that the income of the referral clinic is expected to decrease. CONCLUSIONS: For the improvement of the medical insurance reimbursement system, the administrative fee for the referral clinic and the test fee for the independent medical laboratory should be reimbursed directly to the respective organizations. These changes could be made possible with the proper analysis of medical costs and the development of an effective EDI reimbursement system.

[Biosafety of microbiological laboratories in Korea].

OBJECTIVES: The biosafety level (BSL) practiced in microbiology laboratories in Korea according to the laboratory biosafety manual published by the World Health Organization (WHO) was evaluated using the data obtained by a survey. METHODS: Under the advise of Clinical Laboratory Physicians, 144 types of microorganisms were screened based on the guidelines of biosafety in microbiological and biomedical laboratories published by the US Center for Disease Control and Prevention and classified into 1-4 risk groups. A questionnaire containing 21 questions in 5 areas was developed using the biosafety manual by published WHO. Of the 1,876 different organizations sent the survey, 563 responded to the survey (response rate: 30.0%). The species of microoganisms handled by as well as the biosafety level in microbiology laboratories were analyzed. RESULTS: There were 123 species of microorganisms handled in microbiology labs in Korea. The BSL required in 512 microbiology labs was answered by the survey responders as the first grade in 33 labs (6.4%), 2nd in 437 (85.4%), 3rd in 42 (8.2%), and 4th in none. The average number of items satisfied was 12.2, showing only a 57.9% satisfactory rate and normal distribution. CONCLUSIONS: The state of overall observance of BSL in most microbiology labs of Korea was evaluated as lagging compared with the standard set up by WHO. Therefore, the Korean government need to produce and distribute a biosafety manual in microbiology laboratories and make efforts to prevent this threat through measures such as training in biosafety in microbiology labs.