Performance evaluation of two immunoassays for 25-hydroxyvitamin D

Towards defining optimal concentrations of micronutrients in adults to optimize health

Micronutrients are essential for maintaining physiological homeostasis and optimizing healthspan, defined as the years lived in good health without chronic diseases or disabilities. Despite increasing global life expectancy, improvements in healthspan have not kept pace, partly due to subclinical micronutrient deficiencies that often precede clinical symptoms. The triage theory highlights how micronutrient insufficiencies compromise long-term health by prioritizing critical metabolic functions. Micronutrients such as Vitamins B6, B9, B12, D, and K are particularly crucial to optimizing healthspan, by influencing energy metabolism, neurological health, immune regulation, and bone integrity. Traditional tools like Dietary Reference Intakes (DRIs) provide population-level guidelines but fail to account for individual factors such as genetics, lifestyle, and nutrient interactions. Quantitative assessment of micronutrient concentrations using biomarkers offers a more precise approach but faces challenges, including high costs and limited accessibility. National nutrition surveys demonstrate potential in addressing population-level deficiencies and form the basis for advancing precision supplementation strategies to improve health outcomes and extend healthspan by defining optimal micronutrient concentrations. Future efforts should aim to establish evidence-based thresholds for optimal micronutrient concentrations by integrating biomarker data with clinical outcomes, genetic profiles, and lifestyle factors, providing a framework to guide personalized and population-level supplementation strategies.

Efficacy and safety of high-dose intramuscular vitamin D2 injection in type 2 diabetes mellitus with distal symmetric polyneuropathy combined with vitamin D insufficiency: study protocol for a multicenter, randomized, double-blinded, and placebo-controlled trial

Background

Distal symmetric polyneuropathy (DSPN) is the most common chronic complication of type 2 diabetes mellitus (T2DM). DSPN may lead to more serious complications, such as diabetic foot ulcer, amputation, and reduced life expectancy. Observational studies have suggested that vitamin D deficiency may be associated with the development of DSPN in T2DM. However, interventional studies have found that low-dose vitamin D supplementation does not significantly improve neuropathy in DSPN. This study aims to evaluate the efficacy and safety of intramuscular injection of high-dose vitamin D (HDVD) in T2DM with DSPN combined with vitamin D insufficiency.

Methods and analysis

We will conduct a multicenter, randomized, double-blinded, and placebo-controlled trial in four large hospitals. All eligible participants will be randomly assigned to either the vitamin D₂ supplement or placebo control group and injected intramuscularly monthly for 3 months. Additionally, anthropometric measurements and clinical data will be collected at baseline and 3 months. Adverse events will be collected at 1, 2, and 3 months. The primary outcome measure is the change in the mean Michigan Neuropathy Screening Instrument (MNSI) score at baseline and 3 months post-intervention. We will use the gold-standard liquid chromatography-tandem mass spectrometry method to distinguish between 25(OH)D₂ and 25(OH)D₃ levels. The MNSN score before the intervention will be used as a covariate to compare the changes between both groups before and after the intervention, and the analysis of covariance will be used to analyze the change in the MNSI score after HDVD supplementation.

Discussion

Glycemic control alone does not prevent the progression of DSPN in T2DM. Some studies have suggested that vitamin D may improve DSPN; however, the exact dose, method, and duration of vitamin D supplementation are unknown. Additionally, neuropathy repair requires HDVD supplementation to sustain adequate vitamin D levels. This once-a-month intramuscular method avoids daily medication; therefore, compliance is high. This study will be the first randomized controlled trial in China to analyze the efficacy and safety of HDVD supplementation for patients with T2DM and DSPN and will provide new ideas for pharmacological research and clinical treatment of diabetic neuropathy.

Clinical trial registration

https://www.chictr.org.cn/, identifier ChiCTR2200062266.

An ultrasensitive UHPLC-ESI-MS/MS method augmented with a controlled microwave derivatization reaction for quantitation of vitamin D3 and its major metabolites in COVID-19 patients

It is established that vitamin D deficiency is correlated with the disease severity in COVID-19 patients. However, the reliable and sensitive quantitation of vitamin D3 (D3) and its metabolites remains a difficult challenge. Herein, a novel ultrasensitive and reliable UHPLC-ESI-MS/MS method was developed and validated for the quantitation of D3 and its major metabolites in COVID-19 patients. The mass spectral sensitivity was augmented via controlled microwave-assisted derivatization reaction (CMDR) with 2-nitrosopyridine (Pyr-NO) at 65 °C for 2 min. CMDR hyphenation with UHPLC-MS/MS improves detection sensitivity while shortening separation and derivatization reaction times. The precursor to product ion transitions for D3, 25-hydroxy D3 (25(OH)D3), 1,25-dihydroxy D3 (1,25-(OH)2D3) and calcipotriol (CPT) as an internal standard were m/z 493.4 → 231.3, m/z 509.4 → 231.3, m/z 525.4 → 247.3, and m/z 521.4 → 247.3; respectively. The separation of the formed derivatives was conducted using a gradient elution mode with mobile phase A: formic acid (0.1%) in water and mobile phase B: formic acid (0.1%) in acetonitrile. The elution started with 40% (v/v) of B for 0.3 min then increased linearly to 90% (v/v) at 2 min on an Agilent EclipsePlus C18 (50 × 2.1 mm, 1.8 μm) column at a flow rate of 0.3 mL min⁻¹. The method was validated using FDA standards for bioanalytical method validation over a concentration range of 0.02–50 ng mL⁻¹ with correlation coefficient ≥0.9987 and the lower limit of quantitation (LLOQ) were 0.02–0.05 ng mL⁻¹ in human plasma. The developed method has demonstrated excellent comparability to a well-established chemiluminescent immunoassay (CLIA) method for the analysis of D3 metabolites in human samples. The developed UHPLC-ESI-MS/MS method was implemented for routine and reliable quantitation of D3 and its major metabolites in COVID-19 patients.

Vitamin D - current stage of knowledge about analysis and supplementation

Nowadays, topics related to the proper nutrition of the body, which requires a complex of compounds and supplementation of these ingredients have undoubtedly gained popularity, so it should come as no surprise that there is a widespread interest in vitamin D in science, medicine, analytics and nutrition. In the world of developing technologies, new directions of physiological action of this vitamin on the body are being discovered. Issues related to the demand for vitamin D in various populations and its sources in food, the appropriate form of supplementation, safety and toxicity are extremely important. The present manuscript focuses on the concise evaluation of key data in the field of vitamin D. Structure and physicochemical properties, demand and delivery trails, deficiency and its diagnosis, supplementation, interactions of vitamin D with supplements and drugs are discussed. Attention has also been paid to the methods of vitamin D analysis in various matrices, which allow for an accurate and precise quality assessment of dietary supplements, drugs and food products. The presented information allows deeper understanding of the mechanisms responsible for the development of many diseases in the context of vitamin D levels.

Long-Term Bioavailability of Single Doses of Intramuscular Vitamin D2

OBJECTIVE

We sought to determine the long-term bioavailability of single doses of intramuscular (IM) vita-min D₂ (D₂) in healthy adults.

METHODS

Forty healthy volunteers with hypovitaminosis D received a single dose of 200,000, 400,000, or 600,000 IU intramuscular D₂ or no treatment. Levels of 25-hydroxyvitamin D₂ (25[OH]D₂) and 25-hydroxyvitamin D₃ (25[OH]D₃) in serum were measured by liquid chromatography-tandem mass spectrometry. Vitamin D binding protein (DBP) and intact parathyroid hormone (iPTH), bone turnover markers (BTMs), and serum and urinary calcium were also measured.

RESULTS

After a single dose of D₂ injection, the level of 25(OH)D₂ increased slowly and reached a plateau at 8 weeks. The plateau remained stable for 12 weeks. The mean increase in 25(OH)D₂ was 6.8, 9.6, or 15.6 ng/mL after injection of 200,000 IU, 400,000 IU, or 600,000 IU D₂. Although endogenous 25(OH)D₃ levels were reduced by IM D₂, the total 25(OH)D levels increased by 5.0, 7.0, or 10.3 ng/mL in average after injection of 200,000 IU, 400,000 IU, or 600,000 IU D₂. The iPTH levels were also decreased by IM D₂. However, levels of serum calcium, BTMs, and DBP and urinary calcium were not altered by IM D₂.

CONCLUSION

A single dose of 200,000 IU, 400,000 IU, or 600,000 IU IM D₂ raises total 25-hydroxyvitamin D levels by 5.0, 7.0, or 10.3 ng/mL on average for at least 12 weeks and reduces iPTH and endogenous 25(OH)D₃ levels without affecting levels of serum calcium, BTMs, DBP, and urinary calcium.

Prevalence and correlates of vitamin D deficiency in a tropical setting: results from a nationally representative survey

BACKGROUND

The prevalence of vitamin D deficiency (VDD) may be high in countries with abundant sun exposure year-round, but nationally representative data are lacking.

OBJECTIVE

We examined the prevalence and distribution of VDD by individual and environmental characteristics in a nationally representative sample of Colombian children, pregnant women, and adult nonpregnant women.

METHODS

Using the 2015 Colombian National Nutrition Survey, we defined VDD and low vitamin D (LVD) as serum 25-hydroxyvitamin D [25(OH)D] <30 nmol/L and <50 nmol/L, respectively, in 31,841 children aged 1 to <18 y, 1262 pregnant women, and 7170 nonpregnant women aged 18-49 y. Within each group, we compared VDD and LVD prevalence by levels of sociodemographic, anthropometric, and geographic factors using adjusted prevalence ratios with 95% CIs from multivariable Poisson regression.

RESULTS

The mean ± SE 25(OH)D was 65.1 ± 0.4 nmol/L. The prevalence ± SE of VDD and LVD was 3.1% ± 0.3% and 23.9% ± 0.8%, respectively. Pregnant women had the highest VDD prevalence at 6.7% ± 1.5%, whereas toddlers had the highest prevalence of LVD at 42.5% ± 1.8%. Altitude was one of the strongest correlates of VDD and LVD, with every 100 m above sea level related to a 4% increase in LVD prevalence (P <0.0001). Among children, VDD was positively associated with BMI-for-age Z >1 and maternal education. Among pregnant women, VDD was positively related to education. Among adult nonpregnant women, VDD was associated with BMI and household wealth.

CONCLUSION

The prevalence of VDD and LVD in Colombian women and children is nonnegligible; some age groups are disproportionately affected. Altitude was a strong predictor of vitamin D status in this tropical setting. VDD was positively related to indicators of higher socioeconomic status.

Determinants and Measurement of Neonatal Vitamin D: Overestimation of 25(OH)D in Cord Blood Using CLIA Assay Technology

CONTEXT

Vitamin D (VD) deficiency in pregnancy and the neonatal period has impacts on childhood outcomes. Maternal VD sufficiency is crucial for sufficiency in the neonate, though the effect of early versus late pregnancy 25-hydroxy-vitamin D (25(OH)D) levels on neonatal levels is unknown. Furthermore, chemiluminescence immunoassays (CLIAs) are widely used, though their validity in measuring 25(OH)D specifically in cord blood specimens has not been established.

OBJECTIVE

To assess the validity of a CLIA in the measurement of cord blood 25(OH)D and to evaluate maternal determinants of neonatal 25(OH)D, including early versus late pregnancy 25(OH)D levels.

DESIGN

This is an ancillary analysis from the Vitamin D Antenatal Asthma Reduction Trial (VDAART), a randomized, double-blinded, placebo-controlled study.

PARTICIPANTS AND INTERVENTION

A total of 881 pregnant women at high risk of having offspring asthma were randomized to receive VD supplementation or placebo. Serum samples were collected from mothers in early and late pregnancy and from offspring cord blood at birth. 25(OH)D levels were assayed by CLIA in all maternal and offspring samples and by LC-MS/MS in all offspring samples and a subset of 200 maternal third trimester samples.

RESULTS

Cord blood 25(OH)D levels were higher as measured by CLIA (mean 37.13 ng/mL [SD 18.30]) than by LC-MS/MS (mean 23.54 ng/mL [SD 11.99]), with a mean positive bias of 13.54 ng/mL (SD 12.92) by Bland-Altman analysis. This positive bias in measurement by CLIA was not observed in maternal samples. Third trimester 25(OH)D was a positive determinant of neonatal 25(OH)D levels.

CONCLUSION

Chemiluminescence immunoassays overestimate 25(OH)D levels in human cord blood samples, an effect not observed in maternal blood samples. The quantification of 25(OH)D by CLIA should therefore not be considered valid when assayed in cord blood samples. Third trimester, but not first trimester, maternal 25(OH)D is one of several determinants of neonatal 25(OH)D status.

Vitamin D status in early childhood is not associated with cognitive development and linear growth at 6-9 years of age in North Indian children: a cohort study

BACKGROUND

Vitamin D is important for brain function and linear growth. Vitamin D deficiency during pregnancy has been linked with impaired neurodevelopment during early childhood. However, there is limited evidence from population-based studies on the long-term impact of vitamin D deficiency on cognitive development and linear growth. The objective of the current analysis is to examine whether vitamin D deficiency during infancy and early childhood is associated with cognitive development and linear growth measured in school age.

METHODS

This is a follow-up study of a placebo-controlled trial among 1000 North Indian children 6-30 months of age. We measured growth and neurodevelopment in 791 of these children when they were 6-9 years old. Neurodevelopment was measured using the Wechsler Intelligence Scale for Children, 4th edition ^INDIA, the Crichton Verbal Scale, NEPSY-II subtests, and the BRIEF 2. We categorized vitamin D concentrations during infancy and early childhood according to the US Institute of Medicine's recommendations; serum 25(OH)D < 12 ng/ml as deficient; 12-20 ng/ml as inadequate; > 20 ng/ml as sufficient. In multivariable regression models, adjusting for relevant confounders, we estimated the association between vitamin D status, growth and neurodevelopmental outcomes.

RESULTS

Among the 791 children, baseline vitamin D status was available for 716. Of these, 45.8% were vitamin D deficient, 32.7% were inadequate, and 21.5% were sufficient. Vitamin D status was not associated with any of the cognitive outcomes or linear growth [Adjusted β coefficient for height for age z-score between deficient and sufficient children was - 0.06 (95% CI - 0.24 to 0.11)] at follow up.

CONCLUSION

Our findings do not support the notion that poor vitamin D status in early childhood is an important limitation for cognitive development and linear growth.

TRIAL REGISTRATION

The trial was first registered at www.clinicaltrials.gov as NCT00717730 in July, 2008, and at CTRI/2010/091/001090 in August, 2010 and then as CTRI/2016/11/007494 in November 2016.

Association between serum 25-hydroxyvitamin D concentrations and metabolic syndrome in the middle-aged and elderly Chinese population in Dalian, northeast China: A cross-sectional study

AIMS/INTRODUCTION

To investigate the association between serum 25-hydroxyvitamin D (25-[OH]D) concentrations and metabolic syndrome (MetS) in the middle-aged and elderly Chinese population.

METHODS

The present study included 2,764 participants (aged >50 years). The joint interim statement was used for the standard definition of MetS. Serum 25-(OH)D concentrations were measured by electrochemiluminescence immunoassay. The study participants were categorized into quartiles based on serum 25-(OH)D concentrations, and the quartiles were calculated for the differences using anova and the χ2 -test for continuous and categorical data, respectively. A logistic regression analysis model was applied to estimate the odds ratios and 95% confidence intervals (95% CI) for each quartile of serum 25-(OH)D concentrations compared with the highest quartile.

RESULTS

Serum 25-(OH)D levels were markedly lower in men in the MetS group than in those without MetS. We observed a negative correlation between the higher quartiles of serum 25-(OH)D levels and the presence of MetS among men. The correlation between serum 25-(OH)D levels and the prevalence of MetS persisted even after adjusting for potential confounders, including age, cigarette smoking status, alcohol consumption, physical activity, low-density lipoprotein, creatinine and total serum cholesterol. Adjusted odds ratios of MetS in the second through fourth compared with the lowest quartile for serum 25-(OH)D levels were 0.93 (95% CI 0.54-1.59), 0.89 (95% CI 0.50-1.56) and 0.48 (95% CI 0.28-0.84), respectively.

CONCLUSIONS

Decreased serum 25-(OH)D level is significantly correlated with MetS in middle-aged men.

Serum Parathyroid Hormone and 25-Hydroxyvitamin D Concentrations Before and After Biliopancreatic Diversion

BACKGROUND

Biliopancreatic diversion with duodenal switch (BPD-DS) decreases vitamin D and calcium absorption, which may result in secondary hyperparathyroidism. This study aimed at evaluating the prevalence of vitamin D deficiency and secondary hyperparathyroidism before and after BPD-DS.

METHODS

A retrospective analysis of patients who had undergone BPD-DS at a tertiary bariatric center between 2003 and 2010 and for whom simultaneous measurements of serum 25-hydroxyvitamin D and parathyroid hormone were available within 5 years post-op was performed. The prevalence of vitamin D deficiency (< 20 ng/ml) and secondary hyperparathyroidism (> 65 pg/mL) at different time points was calculated.

RESULTS

Included were 1436 patients (mean ± SD, age 42.7 ± 10.4 years; BMI 51.5 ± 8.6 kg/m²; 69.8% women). Prevalence of vitamin D deficiency decreased up to 6-12 months after surgery (from 35.8% at baseline down to 6-9%) then rose progressively, plateauing at 15.5% after 36 months. Prevalence of hyperparathyroidism was 28.5% before surgery and rose progressively after surgery, reaching 68.6% at 5 years. Mean serum corrected calcium increased from 0 to 6 months then decreased up to 36 months. Preoperatively, the prevalence of hypocalcemia was 7.3%. It increased after 12 months, attaining 26.9% at 48 months.

CONCLUSIONS

Prevalence of vitamin D deficiency and secondary hyperparathyroidism is high before BPD-DS. Despite a low prevalence of vitamin D deficiency after surgery, prevalence of hyperparathyroidism increased steadily 1 year after surgery, preceded by a decrease in serum calcium. Factors explaining the high prevalence of secondary hyperparathyroidism after BPD-DS and its long-term impact on bone health should be addressed.

Development of a method for multiple vitamin D metabolite measurements by liquid chromatography coupled with tandem mass spectrometry in dried blood spots

There are two forms of vitamin D which are essential to the human body, i.e. vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). The inactive metabolites of vitamin D are commonly used for quantitative analysis because of their longer half-life, stability, and relatively high blood concentrations. This paper presents the development of a high-throughput and sensitive method for determining four vitamin D metabolites in dried blood spots using liquid chromatography coupled with tandem mass spectrometry. This method allows for the determination of 25(OH)D2 and 25(OH)D3 concentrations, as well as the epimeric form 3-epi-25(OH)D3 and 24,25(OH)2D3. The analyzed material is capillary blood taken from the fingertip, deposited on filter paper. Four different chromatographic columns were tested to separate all compounds, in particular, the epimeric form. The column of choice was F5 (Phenomenex, Torrance, CA, USA). In order to prove the consistency between the results for DBS, used as an alternative biological matrix, and serum, comparative studies of these two materials were carried out in nearly 100 individuals. The results indicated their positive correlation. The evaluation of short-term stability of metabolites in DBS within the month showed no change in metabolite concentration. During the validation, the impact of the matrix on the ionization of the tested compounds was evaluated. Capillary blood and venous blood collected for different anticoagulants were also compared. The smallest differences in the results were obtained for citrate. In order to achieve a limit of quantitation of 0.2 ng ml-1, sample preparation involved derivatization using a Cookson-type reagent, 4-(4'-dimethylaminophenyl)-1,2,4-triazoline-3,5-dione (DAPTAD).

Prevalence of Vitamin D Inadequacy Among Chinese Postmenopausal Women: A Nationwide, Multicenter, Cross-Sectional Study

Purpose: We aimed to investigate the status of serum 25-hydroxyvitamin D [25(OH)D] among Chinese postmenopausal women in a multicenter cross-sectional study. Methods: Non-institutionalized postmenopausal women aged ≥55 years were recruited from urban and rural areas in 7 geographically different regions in China. Subject enrollment was executed during the summer and the winter. Vitamin D insufficiency and deficiency were defined as 25(OH)D < 30 and< 20 ng/ml, and was measured by liquid chromatography-tandem mass spectrometry. Women were referred to a dual-energy x-ray absorptiometry (DXA) if they had a medium-to-high fracture risk suggested by Osteoporosis Self-Assessment Tool for Asians (OSTA). Results: Among all subjects, 91.2% (1,535/1,684, 95%CI: 89.7, 92.5) had vitamin D insufficiency and 61.3% had vitamin D deficiency (1,033/1,684, 95%CI: 59.0, 63.7). The prevalence of vitamin D deficiency was significantly higher in urban dwellers (64.9 vs. 57.7% in rural, P = 0.002) and in winter-enrolled subjects (84.7 vs. 41.3% in summer, P < 0.0001). The prevalence of vitamin D inadequacy did not increase in trend by latitude and was numerically lower in women who had high fracture risk and osteoporosis. A non-curvilinear change of intact parathyroid hormone (iPTH) levels was observed at 25(OH)D >16.78 ng/mL. Conclusions: The prevalence of vitamin D inadequacy was remarkable among Chinese postmenopausal women and independent of fracture risk assessed by OSTA or osteoporosis suggested by DXA. Winter season, urban residence, however not latitude, were significantly associated with a higher likelihood of vitamin D deficiency. Optimal vitamin D status for iPTH and bone-related outcomes merits further investigation in this population.

Looking beyond linear regression and Bland-Altman plots: a comparison of the clinical performance of 25-hydroxyvitamin D tests

Background:

The systematic evaluation of the clinical concordance of various 25-hydroxyvitamin D (25OHD) testing methods is presented. The need for this approach is raised by the discrepancies in the analytical performance of the available assays.

Methods:

The analytical and clinical performance of six automated 25OHD assays and an in-house liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was investigated. Leftover serum samples (n=162, SA: n=114) were analyzed and all 21 assay combinations were evaluated. The utility of Cohen’s κ values was assessed by transforming them into minimum percentage agreement (MPA). McNemar’s hypothesis test was employed for testing the symmetry of the disagreeing classification outcomes within each method pair.

Results:

Depending on the assay method, the ratio of results classified as positive (<20 ng/mL) was 13.5%–40.0%. The percentage agreement (PA) was 74.1%–92.6%. Compared to other methods, significantly more hypovitaminosis cases were delivered by DiaSorin Liaison® 25 OH vitamin D Total (DL) and significantly fewer by IDS-iSYS 25-Hydroxy Vitamin DS (II). The strongest clinical concordance was exerted by II vs. LC-MS/MS. The κ-derived MPA showed close similarity to the PA scores. McNemar’s tests confirmed the asymmetry of the disagreement in the classification in 14 method combinations.

Conclusions:

The presented approach allows the prediction of the clinical consequences of a 25OHD method transfer. Differences in the clinical classification of assay results are likely encountered when transferring to a new method, even between assays standardized according to the Vitamin D Standardization Program (VDSP) Reference Method Procedure (RMP).

Comparison of two methods for measuring 25-OH vitamin D in the follow-up of patients after bilio-pancreatic diversion bariatric surgery

OBJECTIVE

Our objective was to compare the ECLIA from Roche versus the LC-MS/MS method for quantitation of serum 25-hydroxy-vitamin D in patients who have undergone bariatric surgery.

DESIGN AND METHODS

Cross-sectional and correlational studies were performed on three different groups for the 25-OH-D levels quantitated by both methods. The control group of apparently healthy subjects was randomly selected in a clinical chemistry laboratory. Test groups were patients who had undergone bilio-pancreatic diversion (BPD) and were supplemented either with vitamin D₂ or with vitamin D₃. The number of samples per group was established according to the CLSI recommendation protocol (EPO9-A2-IR).

RESULTS

The agreement of LC-MS/MS with the Roche method was acceptable in the apparently healthy subjects group and in the post-BPD D₃-supplemented group with an average bias of -1.7% and -9.2%, respectively. However, this agreement was unacceptable in the post-BPD D₂-supplemented group with an average bias of -45.3%. The LC-MS/MS enabled us to detect four patients who had excess vitamin D or poisoning with vitamin D for which it was necessary to stop the supplementation with vitamin D in the D₂ -supplemented group.

CONCLUSION

Despite the apparent good agreement between the Roche method and LC-MS/MS in the healthy subjects group and in the post-DBP D₃-supplemented patient group, a considerable bias seems to exist, particularly in the presence of D₂. The LC-MS/MS method is therefore the most accurate method to follow the vitamin D₂ -supplemented bariatric population.