Vitamin D Metabolites: Analytical Challenges and Clinical Relevance

Abstract

Recent research activities have provided new insights in vitamin D metabolism in various conditions. Furthermore, substantial progress has been made in the analysis of vitamin D metabolites and related biomarkers, such as vitamin D binding protein. Liquid chromatography tandem mass spectrometric (LC–MS/MS) methods are capable of accurately measuring multiple vitamin D metabolites in parallel. Nevertheless, only 25(OH)D and the biologically active form 1,25(OH)2D are routinely measured in clinical practice. While 25(OH)D remains the analyte of choice for the diagnosis of vitamin D deficiency, 1,25(OH)2D is only recommended in a few conditions with a dysregulated D metabolism. 24,25(OH)2D, free and bioavailable 25(OH)D, and the vitamin D metabolite ratio (VMR) have shown promising results, but technical pitfalls in their quantification, limited clinical data and the lack of reference values, impede their use in clinical practice. LC–MS/MS is the preferred method for the measurement of all vitamin D related analytes as it offers high sensitivity and specificity. In particular, 25(OH)D and 24,25(OH)2D can accurately be measured with this technology. When interpreted together, they seem to provide a functional measure of vitamin D metabolism beyond the analysis of 25(OH)D alone. The determination of VDBP, free and bioavailable 25(OH)D is compromised by unresolved analytical issues, lacking reference intervals and insufficient clinical data. Therefore, future research activities should focus on analytical standardization and exploration of their clinical value. This review provides an overview on established and new vitamin D related biomarkers including their pathophysiological role, preanalytical and analytical aspects, expected values, indications and influencing conditions.

Vitamin D metabolites and analytical challenges

“…While the many standardization initiatives have undoubtedly improved the validity of 25(OH)D data acquired with automated immunoassays, external quality assurance procedures still display inadequate variability. 19…”

“…94 While the many standardization initiatives have undoubtedly improved the validity of 25(OH)D data acquired with automated immunoassays, external quality assurance procedures still display inadequate variability. 19 High-performance liquid chromatography (HPLC) HPLC is a recognized analytical technique used to separate, identify and quantify the components of the mixture. 95 It primarily uses a column (stationary phase), a pump pushing the mobile phase into the column, and a detector exhibiting the molecule's retention times.…”

“…Although some recent publications provide an overview of known and recently discovered VD-related metabolites, various approaches, and developments that can be utilized to measure VD in biological samples, not all of the strategies that can be used to evaluate VD are addressed in these studies. 19,20 The measurement of 25(OH)D is the major subject of the investigation. Other VD metabolites that display biological action should also receive special consideration in addition to 25(OH)D. In this study, we attempted to explore the recent trends in measuring different VD metabolites.…”

Improving the effectiveness of vaccination against viral and bacterial pathogens through micronutrient supplementation

“…У пациентов с нормальными уровнями 25(OH)D 3 серопротекция составила 80 % (отношение (ОШ) -0,63; 95%-ный ДИ -0,43-0,91; p = 0,01) [39]. Интересно отметить, что витамин D 3 характеризуется самостоятельным противовирусным влиянием, сопоставимым с эффектами некоторых вакцин, на примере папилломавирусной инфекции [40].…”

Role of the Clinical Laboratory in the Assessment of Metabolic Musculoskeletal Diseases

“…In addition, they emphasised the importance of standardisation or harmonisation of commercial assays for optimal utilisation of these relevant biomarkers. Markus Herrmann and his colleagues have emphasised the significance of good analytical tools such as mass spectrometry coupled with liquid chromatography (LCMS/MS) and the emerging significance of 24,25-dihydroxy vitamin D [11] and the vitamin D metabolite ratio (VMR) to define vitamin D deficiency [12,13]. Vitamins D and K are known to play an important role in musculoskeletal health, despite the fact that different studies have given inconsistent results, as far as vitamin supplementation in vitamin D or K replete individuals.…”