Method Performance Verification of Anti-GAD65 and Anti-Insulin antibody Assays.

BACKGROUND: The aim of this study was to evaluate the performance of chemiluminescence immunoassays for anti-GAD65 and anti-insulin antibodies following user verification guidelines. METHODS: The analytical performance of anti-GAD65 and anti-insulin antibodies using a MAGLUMI 2000 analyzer was verified following user verification guidelines by the Clinical and Laboratory Standards Institute. RESULTS: Performance specifications including precision, linearity, carry-over, cutoffs for positive results, reference intervals, and comparability with pre-existing commercially available radioimmunoassays using patient specimens and certified reference material were verified (coefficients of variation for precision of anti-GAD65 and anti-insulin antibodies were 2.6% and 3.4%, respectively). Comparability assessed using clinical serum specimens showed overall agreement with radioimmunoassay of 87.2% (95% confidence interval 74.8% - 94.0%) for the anti-GAD65 antibody assay and 85.4% (95% confidence interval 71.6% - 93.1%) for the anti-insulin antibody assay. CONCLUSIONS: The results of this study verified the analytical performance of MAGLUMI anti-GAD65 and anti-insulin antibody assays for clinical use.

Utilization of Anti-Thyroid Peroxidase Antibody in Local Clinics and Hospitals and Intraindividual Changes in Korean Patients.

BACKGROUND: Limited data are available for test utilization and intraindividual changes in anti-thyroid peroxidase antibodies (anti-TPO Ab) in Korean patients. METHODS: Using a laboratory information system, we retrospectively investigated longitudinally measured anti-TPO Ab along with thyroid function test (TFT) in Korean patients visiting local clinics. RESULTS: During the two-year study period, 542 test results from 183 Korean patients were requested from 51 local clinics and hospitals. Among all 183 patients, 94 (51.4%) exhibited positive anti-TPO Ab (> 34 IU/mL) at initial measurement. Among them, 13.8% (13/94) changed to negative anti-TPO Ab at least once during follow-up. Among 89 patients with initial negative anti-TPO Ab result, five (5.6%) changed to positive anti-TPO Ab at least once during follow up. CONCLUSIONS: Some patients exhibited qualitative changes in anti-TPO Ab. Future studies are needed to clarify the clinical implication of such changes.

Association Among Glycemic Biomarkers in Korean Adults: Hemoglobin A1c, Fructosamine, and Glycated Albumin.

BACKGROUND: We aimed to investigate the associations between glycemic biomarkers (hemoglobin A1c [HbA1c], fructosamine, and glycated albumin [GA]) in Korean adults. METHODS: We retrospectively reviewed data for HbA1c, fructosamine, and glycated albumin between August 28, 2017, and June 30, 2020, to investigate the association between HbA1c and fructosamine and between HbA1c and GA. RESULTS: Overall, 961 fructosamine and 142 GA tests concurrently measured HbA1c. The equations were HbA1c (%) = 0.0175 x fructosamine (µmol/L) + 1.6255 and HbA1c (%) = 0.2029 x GA + 2.8102, respectively. The absolute difference between estimated and measured HbA1c ranged from -3.4% to 2.1% HbA1c with the fructosamine equation and -3.2% to 2.8% HbA1c with the GA equation. CONCLUSIONS: Fructosamine and GA may be useful adjuncts to HbA1c in Korean patients.

Test Utilization for Thyroid Stimulating Hormone Receptor Antibody and Thyroid Stimulating Immunoglobulin Assays in Korea.

BACKGROUND: We aimed to investigate test utilization of the competition-based M22 thyroid-stimulating hormone receptor antibody (M22-TSH Rc Ab) and thyroid stimulating immunoglobulin (TSI) bioassay in Korea. METHODS: We retrospectively reviewed data on M22-TSH Rc Ab assays and TSI assays from the laboratory information system between January 1, 2015, and June 30, 2020. RESULTS: During the study period, 175,448 TSH-Rc Ab tests and including M22-TSH Ab assays and TSI assays were performed on 99,350 Korean adults (26,251 men and 73,099 women). Among 160,880 M22-TSH Rc Ab tests, 1,992 (1.2%) specimens from 1,771 Korean adults had undergone concurrent measurement with M22-TSH Rc Ab and TSI assays. The overall agreement between the M22-TSH-Rc Ab assay and TSI assay was 88.8% (95% confidence interval 87.3 - 90.1). CONCLUSIONS: The results of this study provide basic information regarding test utilization of the M22-TSH-Rc Ab assay and TSI assay in Korean patients.

Seroprevalence of CMV IgG and IgM in Korean women of childbearing age.

BACKGROUND: The aim of this study was to investigate the seroprevalence of cytomegalovirus (CMV) infection using the serologic status of CMV IgG and IgM antibodies in Korean women of childbearing age. METHODS: We retrospectively reviewed CMV IgG and IgM test results from Korean women aged 15-49 years who underwent testing between January 2009 and December 2019. Seroprevalence of CMV IgG and IgM by year and age was investigated. RESULTS: The study period was 11 years, and among 6837 samples tested, 95.8% were CMV IgG-positive. The seropositivity in women aged 15- <20 years was significantly lower (77.5%) than older age groups. Among 6837 total CMV IgG tests, 75.9% (5186) had concurrently measured CMV IgM results among which 2.4% were IgM-positive. CONCLUSION: Considering the low CMV seropositivity of women younger than 20 years, they may need prenatal education for CMV infection.

Evaluation of the Serum Mac-2 Binding Protein Glycosylation Isomer Test used for Diagnosis and Monitoring of Liver Fibrosis and the Correlation of Mac-2 Binding Protein Glycosylation Isomer with Hemoglobin A1c.

BACKGROUND: Our aims in this study were to evaluate the performance of the Mac-2 binding protein glycosylation isomer (M2BPGi), a liver fibrosis marker, using Sysmex HISCL following user verification guidelines before clinical use. We also evaluated the correlation between M2BPGi and hemoglobin A1c (HbA1c) because HbA1c is known as another biomarker associated with glycosylation. METHODS: The analytical performance of M2BPGi was verified following user verification guidelines by the Clinical and Laboratory Standards Institute. RESULTS: A qualitative, precision experiment for analyte concentrations near the cutoff was verified using quality control materials. The manufacturer's precision claims for the quantitative cutoff index were verified, with coefficients of variation in the range of 1.83 - 4.12%. HbA1c did not significantly contribute to M2BPGi in a multivariate analysis with an age factor. CONCLUSIONS: The analytical performance of M2BPGi in our results verify the manufacturer's claims. Clinical information and other findings, including HbA1c, are needed for clinical applications.