Association of standardized serum 25-hydroxyvitamin D with falls in post-menopausal women.

Unlabelled: Vitamin D status has long been related to falls risk. In this planned secondary analysis of a vitamin supplementation trial in postmenopausal women, standardized 25-hydroxyvitamin D concentration up to 60 ng/mL was not associated with increased falls. Women with 25(OH)D ≥ 60 ng/mL had higher odds of ≥ 2 falls.

Consensus Statement on Vitamin D Status Assessment and Supplementation: Whys, Whens, and Hows.

The 6th International Conference, "Controversies in Vitamin D," was convened to discuss controversial topics, such as vitamin D metabolism, assessment, actions, and supplementation. Novel insights into vitamin D mechanisms of action suggest links with conditions that do not depend only on reduced solar exposure or diet intake and that can be detected with distinctive noncanonical vitamin D metabolites. Optimal 25-hydroxyvitamin D (25(OH)D) levels remain debated.

Vitamin D status and supplementation before and after Bariatric Surgery: Recommendations based on a systematic review and meta-analysis.

Bariatric surgery is associated with a postoperative reduction of 25(OH) vitamin D levels (25(OH)D) and with skeletal complications. Currently, guidelines for 25(OH)D assessment and vitamin D supplementation in bariatric patients, pre- and post-surgery, are still lacking. The aim of this work is to analyse systematically the published experience on 25(OH)D status and vitamin D supplementation, pre- and post-surgery, and to propose, on this basis, recommendations for management.

Determination of 24,25-dihydroxyvitamin D in Vitamin D External Quality Assessment Scheme samples using a reference measurement procedure.

Ninety archived human serum samples from the Vitamin D External Quality Assessment Scheme (DEQAS) were analyzed using a reference measurement procedure (RMP) based on isotope dilution liquid chromatography - tandem mass spectrometry (ID LC-MS/MS) for the determination of 24,25-dihydroxyvitamin D [24,25(OH)D]. These 24,25(OH)D results, in conjunction with concentration values assigned using RMPs for 25-hydroxyvitamin D [25(OH)D] and 25-hydroxyvitamin D [25(OH)D], provide a valuable resource for assessing the accuracy of measurements for 24,25(OH)D and for investigating the relationship between 24,25(OH)D and 25(OH)D. Results for 24,25(OH)D using the RMP were compared to DEQAS consensus values demonstrating that the consensus values were not sufficient to assess the accuracy of measurements among different laboratories and methods.

Serum 1,25-dihydroxyvitamin D levels in the diagnosis and pathogenesis of nutritional rickets - a multivariable re-analysis of a case-control study.

Background: A multivariable logistic regression model resulting from a case-control study of nutritional rickets in Nigerian children suggested that higher levels of serum 25(OH)D may be required to prevent nutritional rickets in populations with low-calcium intakes.

Objectives: This current study evaluates if adding serum 1,25-dihydroxyvitamin D [1,25(OH)D] to that model shows that increased levels of serum 1,25(OH)D are independently associated with risk of children on low-calcium diets having nutritional rickets.

Methods: Multivariable logistic regression analysis was used to model the association between serum 1,25(OH)D and risk of having nutritional rickets in cases (n = 108) and controls (n = 115) after adjusting for age, sex, weight-for age z-score, religion, phosphorus intake and age began walking and the interaction between serum 25(OH)D and dietary calcium intake (Full Model).

Towards harmonization of directly measured free 25-hydroxyvitamin D using an enzyme-linked immunosorbent assay.

The majority of circulating 25-hydroxyvitamin D (25(OH)D) is protein bound and perhaps less available than the free fraction of 25(OH)D; therefore, researchers have proposed that the measurement of free 25(OH)D in human serum may be a better indicator of vitamin D health status than total 25(OH)D. The availability of a new enzyme-linked immunosorbent assay (ELISA) for the determination of free 25(OH)D provides a method for direct measurement of the low levels of non-protein bound 25(OH)D. As an initial step towards harmonization of measurements of free 25(OH)D, the ELISA was used to measure free 25(OH)D in three existing Standard Reference Materials (SRMs): SRM 972a Vitamin D Metabolites in Frozen Human Serum, SRM 2973 Vitamin D Metabolites in Frozen Human Serum (High Level), and SRM 1949 Frozen Prenatal Human Serum.

Intra-trial Mean 25(OH)D and PTH Levels and Risk of Falling in Older Men and Women in the Boston STOP IT Trial.

Context: Supplementation with vitamin D has the potential to both reduce and increase risk of falling, and parathyroid hormone (PTH) may contribute to fall risk.

Objective: To assess the associations of intra-trial mean circulating levels of 25-hydroxyvitamin D [25(OH)D] and PTH on incident falls in healthy older adults.

Design: Observational within a clinical trial.

Interlaboratory comparison of 25-hydroxyvitamin D assays: Vitamin D Standardization Program (VDSP) Intercomparison Study 2 - Part 2 ligand binding assays - impact of 25-hydroxyvitamin D and 24R,25-dihydroxyvitamin D on assay performance.

An interlaboratory comparison study was conducted by the Vitamin D Standardization Program (VDSP) to assess the performance of ligand binding assays (Part 2) for the determination of serum total 25-hydroxyvitamin D [25(OH)D]. Fifty single-donor samples were assigned target values for concentrations of 25-hydroxyvitamin D [25(OH)D], 25-hydroxyvitamin D [25(OH)D], 3-epi-25-hydroxyvitamin D [3-epi-25(OH)D], and 24R,25-dihydroxyvitamin D [24R,25(OH)D] using isotope dilution liquid chromatography-tandem mass spectrometry (ID LC-MS/MS). VDSP Intercomparison Study 2 Part 2 includes results from 17 laboratories using 32 ligand binding assays.

Interlaboratory comparison of 25-hydroxyvitamin D assays: Vitamin D Standardization Program (VDSP) Intercomparison Study 2 - Part 1 liquid chromatography - tandem mass spectrometry (LC-MS/MS) assays - impact of 3-epi-25-hydroxyvitamin D on assay performance.

An interlaboratory comparison study was conducted by the Vitamin D Standardization Program (VDSP) to assess the performance of liquid chromatography - tandem mass spectrometry (LC-MS/MS) assays used for the determination of serum total 25-hydroxyvitamin D (25(OH)D), which is the sum of 25-hydroxyvitamin D (25(OH)D) and 25-hydroxyvitamin D (25(OH)D). A set of 50 single-donor samples was assigned target values for concentrations of 25(OH)D, 25(OH)D, 3-epi-25-hydroxyvitamin D (3-epi-25(OH)D), and 24R,25-dihydroxyvitamin D (24R,25(OH)D) using isotope dilution liquid chromatography - tandem mass spectrometry (ID LC-MS/MS). VDSP Intercomparison Study 2 Part 1 includes results from 14 laboratories using 14 custom LC-MS/MS assays.

Vitamin D Standardization Program (VDSP) intralaboratory study for the assessment of 25-hydroxyvitamin D assay variability and bias.

An intralaboratory study assessing assay variability and bias for determination of serum total 25-hydroxyvitamin D [25(OH)D] was conducted by the Vitamin D Standardization Program (VDSP). Thirteen assays for serum total 25(OH)D were evaluated in a single laboratory including 11 unique immunoassays and one liquid chromatography - tandem mass spectrometry (LC-MS/MS) assay. Fifty single-donor serum samples, including eight samples with high concentrations of 25(OH)D (> 30 nmol/L), were assigned target values for 25(OH)D and 25(OH)D using reference measurement procedures (RMP).

Serum 25-hydroxyvitamin D requirements to prevent nutritional rickets in Nigerian children on a low-calcium diet-a multivariable reanalysis.

Background: Nutritional rickets is believed to result from the interaction of inadequate serum 25-hydroxyvitamin D [25(OH)D] concentration and dietary calcium intake, but this interaction has not been confirmed in children with rickets. Determining the vitamin D requirements to prevent nutritional rickets has been thwarted by inconsistent case definition, inadequate adjustment for calcium intake and other confounders, and 25(OH)D assay variability.

Objectives: To model the 25(OH)D concentration associated with nutritional rickets in calcium-deprived Nigerian children, adjusted for confounding factors, and develop a general approach to define vitamin D status while accounting for calcium intake.

Recommendations on the measurement and the clinical use of vitamin D metabolites and vitamin D binding protein - A position paper from the IFCC Committee on bone metabolism.

Vitamin D, an important hormone with a central role in calcium and phosphate homeostasis, is required for bone and muscle development as well as preservation of musculoskeletal function. The most abundant vitamin D metabolite is 25-hydroxyvitamin D [25(OH)D], which is currently considered the best marker to evaluate overall vitamin D status. 25(OH)D is therefore the most commonly measured metabolite in clinical practice.

Controversies in Vitamin D: A Statement From the Third International Conference.

The Third International Conference on Controversies in Vitamin D was held in Gubbio, Italy, September 10-13, 2019. The conference was held as a follow-up to previous meetings held in 2017 and 2018 to address topics of controversy in vitamin D research. The specific topics were selected by the steering committee of the conference and based upon areas that remain controversial from the preceding conferences.

Adjusting Coronavirus Prevalence Estimates for Laboratory Test Kit Error.

Testing representative populations to determine the prevalence or the percentage of the population with active severe acute respiratory syndrome coronavirus 2 infection and/or antibodies to infection is being recommended as essential for making public policy decisions to ease restrictions or to continue enforcing national, state, and local government rules to shelter in place. However, all laboratory tests are imperfect and have estimates of sensitivity and specificity less than 100%-in some cases, considerably less than 100%. That error will lead to biased prevalence estimates.

The measurement of vitamin D metabolites part II-the measurement of the various vitamin D metabolites.

Today, the possibility exists to measure a number of different vitamin D metabolites with accurate and precise methods. The most abundant vitamin D metabolite, 25(OH)D, is considered the best marker for estimating vitamin D status and is therefore the most commonly measured in clinical practice. There is no consensus on the added value of measuring other metabolites beyond 25-hydroxyvitamin D, although, in some special clinical scenarios and complicated cases, these metabolites may provide just the information needed for an accurate diagnosis.

The measurement of vitamin D metabolites: part I-metabolism of vitamin D and the measurement of 25-hydroxyvitamin D.

It has been more than 80 years since the discovery of vitamin D and its ability to cure rickets in children. Vitamin D is a secosteroid and comes in two distinct forms, vitamin D2 and vitamin D3. During the last 40 years, the synthesis and metabolism of vitamin D were elucidated and more than 50 metabolites of vitamin D have been discovered, though commercial measurement procedures have been developed for only a few of them.

The Association between Cardiovascular Disease Risk Factors and 25-Hydroxivitamin D and Related Analytes among Hispanic/Latino Adults: A Pilot Study.

Although the association of vitamin D levels with cardiovascular risk profiles among Hispanics/Latinos has been studied, little is known about this association among Hispanics/Latinos with chronic conditions. This pilot study determined serum vitamin D and parathyroid hormone (PTH) levels in a sample of participants from the University of Illinois at the Chicago Cohort of Patients, Family and Friends (UIC Cohort) and examined their association with traditional cardiovascular disease risk factors. From July 2012 to June 2016, the UIC Cohort study enrolled and conducted clinical examinations on men and women ages 18 years and older, who had one or more diagnosed chronic diseases/conditions (excluding cancer).

Effect of Genetically Low 25-Hydroxyvitamin D on Mortality Risk: Mendelian Randomization Analysis in 3 Large European Cohorts.

The aim of this study was to determine if increased mortality associated with low levels of serum 25-hydroxyvitamin D (25(OH)D) reflects a causal relationship by using a Mendelian randomisation (MR) approach with genetic variants in the vitamin D synthesis pathway. Individual participant data from three European cohorts were harmonized with standardization of 25(OH)D according to the Vitamin D Standardization Program. Most relevant single nucleotide polymorphisms of the genes (rs12794714, rs10741657) and (rs12785878, rs11234027), were combined in two allelic scores.

Prevalence and Determinants of QuantiFERON-Diagnosed Tuberculosis Infection in 9810 Mongolian Schoolchildren.

Background: There is controversy regarding the potential influence of vitamin D deficiency, exposure to environmental tobacco smoke, BCG vaccination, season, and body habitus on susceptibility to Mycobacterium tuberculosis (MTB) infection.

Methods: We conducted a cross-sectional analysis to identify determinants of a positive QuantiFERON-TB Gold (QFT) assay result in children aged 6-13 years attending 18 schools in Ulaanbaatar, Mongolia. Data relating to potential risk factors for MTB infection were collected by questionnaire, physical examination, and determination of serum 25-hydroxyvitamin D (25[OH]D) concentrations.

Controversies in Vitamin D: Summary Statement From an International Conference.

Context: Vitamin D is classically recognized as a regulator of calcium and phosphorus metabolism. Recent advances in the measurement of vitamin D metabolites, diagnosis of vitamin D deficiency, and clinical observations have led to an appreciation that along with its role in skeletal metabolism, vitamin D may well have an important role in nonclassical settings. Measurement of the circulating form of vitamin D that best describes total body stores, namely 25-hydroxyvitamin D, can be unreliable despite many sophisticated methodologies that have been proposed and implemented.

Implications of standardization of serum 25-hydroxyvitamin D data for the evaluation of vitamin D status in Germany, including a temporal analysis.

Background: Comparability of 25-hydroxyvitamin D (25(OH)D) measurements is hampered by method-related differences in measurement values. International standardization of laboratory assays has been suggested to solve this problem.

Methods: As part of the European Commission-funded project 'Food-based solutions for optimal vitamin D nutrition and health through the life cycle' (ODIN), original measurements of serum 25(OH)D of three German national health surveys conducted between 1998 and 2011 have been standardized retrospectively.