Serologic Survey of IgG Against SARS-CoV-2 Among Hospital Visitors Without a History of SARS-CoV-2 Infection in Tokyo, 2020-2021.

BACKGROUND: Tokyo, the capital of Japan, is a densely populated city of >13 million people, so the population is at high risk of epidemic severe acute respiratory coronavirus 2 (SARS-CoV-2) infection. A serologic survey of anti-SARS-CoV-2 IgG would provide valuable data for assessing the city's SARS-CoV-2 infection status. Therefore, this cross-sectional study estimated the anti-SARS-CoV-2 IgG seroprevalence in Tokyo. METHODS: Leftover serum of 23,234 hospital visitors was tested for antibodies against SARS-CoV-2 using an iFlash 3000 chemiluminescence immunoassay analyzer (Shenzhen YHLO Biotech, Shenzhen, China) with an iFlash-SARS-CoV-2 IgG kit (YHLO) and iFlash-SARS-CoV-2 IgG-S1 kit (YHLO). Serum samples with a positive result (≥10 AU/mL) in either of these assays were considered seropositive for anti-SARS-CoV-2 IgG. Participants were randomly selected from patients visiting 14 Tokyo hospitals between September 1, 2020 and March 31, 2021. No participants were diagnosed with coronavirus disease 2019 (COVID-19), and none exhibited COVID-19-related symptoms at the time of blood collection. RESULTS: The overall anti-SARS-CoV-2 IgG seroprevalence among all participants was 1.83% (95% confidence interval [CI], 1.66-2.01%). The seroprevalence in March 2021, the most recent month of this study, was 2.70% (95% CI, 2.16-3.34%). After adjusting for population age, sex, and region, the estimated seroprevalence in Tokyo was 3.40%, indicating that 470,778 individuals had a history of SARS-CoV-2 infection. CONCLUSIONS: The estimated number of individuals in Tokyo with a history of SARS-CoV-2 infection was 3.9-fold higher than the number of confirmed cases. Our study enhances understanding of the SARS-CoV-2 epidemic in Tokyo.

Influence of diffuse reflectance measurement accuracy on the scattering coefficient in determination of optical properties with integrating sphere optics (a secondary publication).

An estimation error of the scattering coefficient of hemoglobin in the high absorption wavelength range has been observed in optical property calculations of blood-rich tissues. In this study, the relationship between the accuracy of diffuse reflectance measurement in the integrating sphere and calculated scattering coefficient was evaluated with a system to calculate optical properties combined with an integrating sphere setup and the inverse Monte Carlo simulation. Diffuse reflectance was measured with the integrating sphere using a small incident port diameter and optical properties were calculated. As a result, the estimation error of the scattering coefficient was improved by accurate measurement of diffuse reflectance. In the high absorption wavelength range, the accuracy of diffuse reflectance measurement has an effect on the calculated scattering coefficient.

Comparison of chemiluminescence enzyme immunoassay (CLEIA) with ELISA for the determination of anti-cyclic citrullinated peptide antibodies.

BACKGROUND: Autoantibodies against cyclic citrullinated peptide (anti-CCP) are sensitive and highly specific markers for rheumatoid arthritis (RA). We evaluated the analytical and diagnostic accuracy of chemiluminescence enzyme immunoassay (CLEIA) for anti-CCP antibodies, and compared it with that of ELISA. METHODS: Ninety-nine RA patients who were diagnosed according to the American College of Rheumatology criteria, 16 patients with osteoarthritis, and 94 healthy subjects were included. Sera were used to assess the precision, functional sensitivity, and linearity of anti-CCP antibody determination by CLEIA and the correlation of anti-CCP antibody values between CLEIA and ELISA. RESULTS: For anti-CCP antibodies by CLEIA, the total CV was 4.0 and 5.3% at 21.17 and 90 U/ml, respectively, and the lower limit of detection was 0.1 U/ml. The correlation of CLEIA (x) with ELISA (y) for anti-CCP was: y=1.08x+4.171, r=0.9178 (p<0.0001). No difference was observed in the sensitivity and specificity between CLEIA and ELISA. CONCLUSIONS: The automated CLEIA processing system for determining anti-CCP antibodies showed a good analytical performance, and suggested that the CLEIA system has a potential to provide clinically useful data within a short time.