Background: Limited data are available for validation of low-density lipoprotein cholesterol (LDL) calculation (LDL_cal) in the adult Korean population. The aim of this study was to develop and validate a new equation for LDL_cal and to compare it with previous such equations in a Korean population. Methods: A new equation for LDL_cal was developed (LDL_Choi). LDL_Choi and 11 other previously published equations were applied and compared with directly measured LDL concentration (LDL_direct) in a development cohort (population 1), an independent validation cohort in the same laboratory (population 2), and the Korea National Health and Nutrition Examination Survey 2017 cohort (population 3). Results: Among the 12 equations, the newly-developed equation (LDL_Choi = total cholesterol – 0.87 x high-density lipoprotein cholesterol – 0.13 x triglycerides) had the highest intraclass correlation coefficient (ICC) and the lowest mean systemic difference and median absolute percentage error in populations 1 and 2 but not in population 3. Subgroup analysis showed good agreement between LDL_Choi and LDL_direct (ICC > 0.75) in population 2, whose LDL_direct < 70 mg/dL. For samples with high triglycerides (> 400 mg/dL), equation accuracy varied. Categorization concordance according to the National Cholesterol Education Program Adult Treatment Panel III criteria with the other 11 equations were less than 80%; that of LDL_Choi was 87.6 and 87.4% in populations 1 and 2, respectively. Conclusions: Accuracy of 12 equations for LDL_cal varied by cohort and subgroup based on LDL_direct and triglycerides. A laboratory-specific equation for LDL_cal and/or LDL_direct may be needed for accurate evaluation of LDL status.

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.

Diminished ovarian reserve can be assessed biochemically using serum anti-Müllerian hormone (AMH) and follicle-stimulating hormone (FSH) tests. This study aimed to evaluate the prevalence of diminished ovarian reserve in a large population of reproductive-aged women by age and geographic region in Korea using different cutoffs of serum AMH and FSH levels. In 2022, 13,351 women underwent both AMH and FSH tests. The prevalence of diminished ovarian reserve increased markedly with age. Although cutoffs for AMH and FSH levels are different in USA and Korean guidelines, the overall prevalence of diminished ovarian reserve was comparable. The maximum prevalence was 3.8%, 6.0%, 11.0%, 28.6%, 69.3%, and 95.0% in women aged 20–24, 25–29, 30–34, 35–39, 40–44, and 45–49 years, respectively. The overall prevalence and age-adjusted prevalence of diminished ovarian reserve were 37.2% and 38.4%, respectively. Women who had only increased serum FSH without decreased AMH represented 1.1% (by Korean guidelines) and 2.5% (by USA guidelines) of all women. Serum AMH and FSH tests were underutilized on Jeju Island. The results of this study provide basic knowledge about diminished ovarian reserve for use in infertility support programs and the field of maternal aging.

We retrospectively reviewed serum 25-hydroxy vitamin D (25(OH)D) test results from an adult Korean population visiting local clinics and hospitals between July 2017 and December 2021 to gather recent information on the prevalence of vitamin D deficiency. The prevalence of vitamin D deficiency status was investigated according to criteria offered by various clinical guidelines. During the study period, 180,289 subjects (29,658 men and 150,631 women) were tested for 25(OH)D. The overall prevalence rates of vitamin D deficiency status based on 25(OH)D level were as follows: 0.4% for <5 ng/mL, 12.5% for <10 ng/mL, 20.6% for <12 ng/mL, 49.4% for <20 ng/mL, and <75.3% for <30 ng/mL. Women tested their 25(OH)D level more frequently than men, and the overall prevalence of 25(OH)D < 10 ng/mL was higher among women than men, while that of 25(OH)D <30 ng/mL was lower among women than men. Among age groups, the prevalence of 25(OH)D <30 ng/mL was higher in younger patients (20s–40s, 79.6–85.5%) than older ones (≥50 years, 62.6–69.2%). The overall prevalence of vitamin D deficiency decreased over time from 2018 to 2021. Future studies are needed to clarify the clinical impact of this change.

Objectives The aim of this study was to investigate the immunity against rubella using the serological status of rubella-specific IgG antibodies (antirubella IgG) in Korean women of childbearing age (15–49 years). Design Retrospective cross-sectional study. Setting Population-based cross-sectional study in South Korea. Participants Between January 2010 and December 2017, test results from Korean women aged 15–49 years who had visited an obstetric private clinic (nationwide institutions) and had requested rubella-specific IgG antibody tests from Green Cross Laboratories were obtained from the laboratory information system. Results Between 2010 and 2017, antirubella IgG test results from 328 426 Korean women aged 15–49 years who had visited private obstetric clinics (1438 institutions nationwide) were retrospectively analysed by tested year, age, cohort and geographic regions. Over the 8-year study period, the rate of unimmunised women ranged from 7.8% to 9.7%. Multivariable-adjusted logistic regression models showed that the odds of being immune to rubella (positive and equivocal results of antirubella IgG test) were lower in 2017 compared with 2010, in women in their 40s, in a pre-catch-up cohort and in women living in Incheon, Busan, South Gyeongsang, North and South Jeolla and Jeju provinces (p<0.0001). Conclusions In consideration of the factors associated with prevalence of women unimmunised to rubella, future public health efforts should be focused on catch-up activities. The results of this study could be used to strengthen disease control and prevent rubella, including a nationwide immunisation programme.

Sung-Eun Cho, M.D., Jungsun Han, M.S., Juyoung You, M.S., Jun Hyung Lee, M.D., Ahram Yi, M.D., Sang Gon Lee, M.D., and Eun Hee Lee, M.D.. Ann Lab Med -0001;0:. https://doi.org/10.3343/alm.2024.0072