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Background: We aimed to investigate Krebs von den Lungen 6 (KL-6) assay results in a clinical laboratory to better understand patient population and test utilization. Methods: We investigated serum KL-6 test results in Korean adults by the type of medical institution visited between October 2019 and December 2021. Results: Overall, 7,677 KL-6 tests were performed in 5,527 Korean adults (3,627 men and 1,900 women) with a median age of 68.3 years (interquartile range 59.6 - 75.8). The median KL-6 level in 507 patients who visited health promotion centers was lower than the other 5,020 patients who visited other types of medical institutions (196 U/mL vs. 588.0 U/mL, respectively, p < 0.05). Increased KL-6 levels (≥ 500 U/mL) were observed in 0.8% of patients who visited health promotion centers and in 57.1% of patients who visited other types of medical institutions. Conclusions: This study will help to understand patient populations and test utilization for KL-6 in clinical laboratories in Korea. [ABSTRACT FROM AUTHOR]

Background: Diagnosis of syphilis, a sexually transmitted infection, can be based on clinical information and various combinations of results of both non-treponemal and treponemal assays. Because understanding a patient population is helpful for test utilization in the clinical laboratory, we aimed to investigate the results of syphilis serology tests requested from local clinics in Korea. Methods: We retrospectively evaluated the syphilis serology test results of serum Rapid Plasma Reagin (RPR), Treponema pallidum latex agglutination (TPLA), RPR titer, and fluorescent treponemal antibody absorption (FTA-ABS) IgG, and IgM tests performed in Korean adults in the laboratory information system of Green Cross Laboratories. We investigated the patterns of syphilis serology test results and possible interpretation according to combinations of syphilis serology based on a traditional testing algorithm. Results: During the one-year study period, 33,746 RPR tests were performed in Korean adults (7,622 men and 26,124 women) with a median age of 35.1 years (interquartile range 30.8 - 43.4 years). Among these RPR tests, 317 (0.9%) showed RPR+ results and were performed simultaneous with TPLA tests. Among these 317 patients, 187 (59.0%) had RPR+/TPLA+ results. Among 130 patients with RPR+/TPLA-results, FTA-ABS IgG and IgM were only tested in 15 (11.5%): 14 were IgG-/IgM-, and one who underwent only the IgM test showed a negative result (probably a biological false positive of RPR). Among 187 RPR+/TPLA+ patients, 60 (2.1%) had RPR titer ≤ 1:8, and 10 were FTA-ABS IgM+ (including weak reactive results probably due to current infection or rare biological false-positive). Among 121 patients with RPR+/TPLA+/RPR titer ≤ 1:4, 30 were tested for FTA-ABS IgG and/or IgM: the two FTA-ABS IgM+ (including weak reactive) patients had an RPR titer of 1:4. Conclusions: This study will help to understand patient populations and test utilization for syphilis serology test interpretation in clinical laboratories in Korea. Further studies are needed to investigate the clinical impact of test utilization of syphilis serology in Korea. [ABSTRACT FROM AUTHOR]

Background: The appropriate use of the thyroglobulin (Tg) test involves the concurrent measurement of Tg autoantibodies (Tg Ab) due to the potential for false low or false high Tg due to Tg Ab interference. Methods: We retrospectively reviewed Tg and Tg Ab test results requested from local clinics and hospitals in Korea between July 1, 2020 and June 30, 2021. Results: During the study period, 13,811 Tg tests were performed. Among them, 6,769 Tg tests were identified as being repeatedly measured from 2,988 Korean adults. Among the 6,769 performed Tg tests, 2,733 (40.4%) did not have concurrently performed Tg Ab tests. Among the 2,988 subjects, 1,089 (36.4%) had no concurrently measured Tg Ab test results. Among 4,036 Tg results with concurrently measured Tg Ab, 1,045 (25.9%) had positive Tg Ab results, which could interfere with Tg concentration measurements. Conclusions: The Tg Ab test appears to be underutilized in Korea. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Background: Limited data are available regarding intraindividual changes in the Mac-2 binding protein glycosylation isomer (M2BPGi), a liver fibrosis biomarker, performed for health checkups in Korean subjects. Methods: Through a laboratory information system, we retrospectively investigated longitudinally measured M2BPGi to assess intraindividual changes in M2BPGi test results. Results: During a 38-month study period, 526 test results from 246 Korean subjects undergoing general health checkups were requested from 13 local clinics and hospitals. Among all 246 subjects, 190 (77.2%) exhibited negative M2BPGi (< 1.0 C.O.I.) during the initial measurement. Among all 246 subjects, 210 (85.4%) did not experience any changes in qualitative results during a follow-up. Among 42 subjects with initially 1+ positive results for M2BPGi, 17 (40.5%) changed to a negative M2BPGi result at least once during follow-up. No subjects with initially negative results or 1+ positive (1.0 ≤ C.O.I. < 3.0) results changed to 2+ positive (≥ 3.0 C.O.I.) results during the 38-month follow-up period. Conclusions: Some subjects exhibited qualitative changes in M2BPGi during follow-up health examinations. Future studies are needed to clarify the clinical implication of such changes. [ABSTRACT FROM AUTHOR]

Background: We aimed to investigate serum folate level in Korean women of reproductive age and to evaluate the prevalence of folate deficiency by age using different cutoffs. Methods: We retrospectively reviewed data obtained with a serum folate assay traceable to World Health Organization international standard reference material 03/178. Results: Between September 2017 and June 2019, data from a total of 8,380 Korean women aged 15 - 49 years were obtained. Mean (standard deviation) serum folate concentration for all women was 9.1 (6.7) ng/mL. Prevalence of folate deficiency using the cutoff of < 3 ng/mL was 6.2% and that for < 4 ng/mL was 14.9%. The prevalence of folate deficiency was higher in women of younger age (15 to < 25 years, even > 30% using the cutoff of 4 ng/mL) compared to other age groups. Conclusions: This study suggests that women aged 15 to < 25 years are at high risk of folate deficiency. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Background: Little is known about the reference interval of serum folate concentration if using recently re-standardized assays traceable to the World Health Organization (WHO) international standard reference 03/178 in a Korean population. This study aimed to investigate serum folate levels in Korean subjects without macrocytic anemia or increased homocysteine, for the assessment of folate deficiency. Methods: We retrospectively reviewed data from Korean adults whose hemoglobin, mean corpuscular volume, and serum total homocysteine values were within reference limits. Results: The median (interquartile range) serum folate level was 7.8 (5.4 - 12.6) ng/mL in men and 10.2 (6.9 - 15.6) ng/mL in women. The reference interval for serum folate (2.5th and 97.5th percentiles) ranged from 2.9 to 38.0 ng/ mL. From among 723 Korean adults, the lower limit of reference intervals of serum folate for folate deficiency, defined as the 2.5th percentile, was 2.9 ng/mL. The prevalence of folate deficiency was higher in men (6.5%) than in women (1.2%, p < 0.05) when a cutoff value of 3.0 ng/mL was applied. Using the cutoff value of 4 ng/mL for fo-late deficiency, which is in accordance with the instructions from the manufacturer of the new assay and the WHO 2012 guideline for homocysteine as a metabolic indicator before assay standardization, about 5% of subjects were reclassified as folate deficient. Conclusions: Our study suggests that any change of reference limits using a re-standardized assay needs to be verified in clinical laboratories. [ABSTRACT FROM AUTHOR]

Background: When measuring thyroglobulin (Tg), simultaneous measurement of Tg autoantibodies (Ab) is recommended by clinical guidelines for follow-up of patients with differentiated thyroid cancers after thyroidectomy and radioactive iodine ablation. We aimed to investigate test utilization of Tg and Tg Ab assays in local clinics and hospitals in Korea. Methods: We retrospectively reviewed data from the laboratory information system between November 6, 2017 and December 31, 2019. Results: During the study period, 10,551 Tg tests were performed on 2,592 Korean adults from 97 local clinics and hospitals. Among them, 3,924 (37.2%) test results lacked concurrent Tg Ab assays, while 6,627 test results had concurrently measured Tg Ab, and 528 (8.0%) showed positive Tg Ab results, which could interfere with measurement of Tg concentration. Conclusions: The results of this study provide basic information regarding test utilization of Tg Ab assays to improve test utilization for accurate Tg measurement in Korean patients. [ABSTRACT FROM AUTHOR]

Background: We retrospectively investigated soluble fms-like tyrosine kinase-1 (sFlt-1)/placental growth factor (PlGF) ratios and screen-positive rates according to cutoff values for preeclampsia risk assessment based on the number of fetuses. Methods: sFlt-1/PlGF ratios < 38.0 and < 53.0 were defined as low risk of preeclampsia (screen negative) for singleton and twin pregnancies, respectively. Results: During the study period, 442 test results from 403 pregnant women (374 with singleton and 29 twin pregnancies) from 32 local clinics and hospitals were analyzed. The overall rate of positive preeclampsia screening was 25.1% and this rate was higher when gestational age was ≥ 34 weeks than when it was < 34 weeks (58.7% vs. 18.6%, p < 0.05). Among 34 women with follow-up results, a change in interpretation category was observed during the follow-up period at ≥ 4.8 weeks for singleton and = 1.6 weeks for twin pregnancies, respectively. Conclusions: This study may help to understand the sFlt-1/PlGF ratio in pregnant Korean women. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]