Performance evaluation of Siemens ADVIA Centaur and Roche MODULAR Analytics E170 Total 25-OH Vitamin D assays

Factors to take into account when interpreting 25-hydroxy-vitamin D serum levels

BACKGROUND

Assessing vitamin D status, typically evaluated using serum or plasma 25-hydroxy vitamin D [25(OH)D] concentration, is complex because of various influencing factors.

METHODS

Seasonality significantly affects intra-individual variability in 25(OH)D levels. This variation can be addressed by employing cosinor functions that are tailored to the geographical location of the patient to correct for seasonal effects. In addition to seasonality, genetic factors, such as DBP polymorphism and body composition, particularly adiposity, play crucial roles. Dialysis patients with DBP 2-2 phenotype exhibit higher vitamin D requirements. Genotyping/phenotyping of DBP allows for better tailored vitamin D supplementation. The lipid-soluble nature of vitamin D also interacts with plasma components such as serum triglycerides, which can influence vitamin D measurements. Adiposity, which is negatively correlated with vitamin D concentration, necessitates body mass-based mathematical adjustments for accurate vitamin D assessment in subjects with extreme BMI values.

CONCLUSIONS

Accordingly, vitamin D replacement therapy must be personalized, taking into account factors such as body size and seasonal variations, to effectively reach the target serum 25(OH)D concentrations.

Optimised liquid chromatography tandem mass spectrometry method for the simultaneous quantification of serum vitamin D analogues while also accounting for epimers and isobars

The accurate quantification of multiple vitamin D analogues simultaneously is challenging. This study set out to use liquid chromatography-tandem mass spectrometry (LC-MS/MS) to develop a method capable of measuring a comprehensive vitamin D profile, encompassing twelve vitamin D analogues (vitamin D2, D3, 25(OH)D2, 25(OH)D3, 1,25(OH)2D2, 1,25(OH)2D3, 24,25(OH)2D2, 24,25(OH)2D3, 3-epi-25(OH)D2, 3-epi-25(OH)D3, 7αC4 and1α(OH)D3) in a single run. Serum samples were prepared using double liquid-liquid extraction and analysed on an Agilent 6460 QQQ LC-MS/MS equipped with a Pursuit 3 Pentafluorophenyl (4.6 x 100 mm, 3 μm) column. Recovery rates for all analytes were above 95 % with a coefficient of variation (CV) below 10 %. The method exhibited good linearity (r > 0.995) and had a range of detection limits between 0.01 and 0.35 ng/mL and quantification limits between 0.15 and 0.96 ng/mL. Repeatability and within-lab precision were acceptable, with CV values below 10 % and 15 %, respectively. Method accuracy was excellent, with a systematic error below 6.60 %. additionally, all analytes-maintained stability for 48 h following sample preparation, and no interferences were observed among co-eluting analytes. Lastly, this method achieved "world-class" status according to the Sigma metric scale specifications, requiring minimal quality control to ensure data quality. This successfully validated method has the potential not only for improving vitamin D profiling procedures but also for aiding in the diagnosis of other genetic disorders where measuring beyond 25(OH)D is crucial.

Optimal Serum 25(OH)D Levels and Vitamin D Intake in Korean Postmenopausal Women

Vitamin D plays a crucial role in regulating the growth and maintenance of the musculoskeletal system. Postmenopausal women are vulnerable to bone fractures because of the decrease in bone mineral density (BMD). Therefore, this study aimed to identify the determinants that influence BMD and the 25(OH)D levels in Korean postmenopausal women. This study collected general and dietary intake information, measured biochemical indices, and conducted BMD tests in 96 postmenopausal women residing in a metropolitan area in Korea. This study analyzed factors that influenced serum 25-hydroxyvitamin D (25(OH)D) and BMD, as well as the correlation between the intact parathyroid hormone (iPTH) and serum 25(OH)D levels. The serum 25(OH)D levels increased by 0.226 ng/mL in the summertime, 0.314 ng/mL in the wintertime, and 0.370 ng/mL on annual average when vitamin D intake rose by 1 µg/1000 kcal. When the serum 25(OH)D levels were ≥18.9 ng/mL, the iPTH levels did not rapidly increase. To maintain the serum 25(OH)D levels at ≥18.9 ng/mL, a daily vitamin D intake of ≥13.21 µg was required. Consequently, consuming vitamin D-fortified foods or vitamin D supplements is necessary to improve both bone health and vitamin D nutritional status.

Optimal Serum 25(OH)D Level and Vitamin D Intake in Young Korean Women

Vitamin D status is essential for preventing bone disease. Young Korean women have the highest vitamin D deficiency prevalence compared with other demographic groups. This study aimed to establish the optimal vitamin D intake level for maintaining an adequate serum 25-hydroxyvitamin D (25[OH]D) level by season in young Korean women (mean age: 23.1 years). Each participant (wintertime, n = 101; summertime, n = 117) completed a lifestyle survey, dietary record, bone mineral density, and biochemical tests. Seasonal factors impacting 25(OH)D were identified, vitamin D intake for sufficient 25(OH)D levels was calculated, and the relationship between 25(OH)D and intact parathyroid hormone (iPTH) was analyzed. During summertime, 25(OH)D levels were higher than in wintertime (17.9 vs. 15.0 ng/mL). A 1 µg/1000 kcal increase in vitamin D intake increased 25(OH)D levels by 0.170 ng/mL in wintertime and 0.149 ng/mL in summertime. iPTH levels reached a theoretical plateau corresponding to an 18.4 ng/mL 25(OH)D level. The vitamin D intake threshold for maintaining 25(OH)D levels at ≥20 and ≥18.4 ng/mL was ≥10.97 μg/day. For a sufficient level of 25(OH)D in young Korean women, increasing summertime UV irradiation time and increasing vitamin D supplements and vitamin D-containing foods throughout the year is beneficial.

Effect of Vitamin-D-Enriched Edible Mushrooms on Vitamin D Status, Bone Health and Expression of CYP2R1, CYP27B1 and VDR Gene in Wistar Rats

Vitamin D deficiency is highly prevalent in India and worldwide. Mushrooms are important nutritional foods, and in this context shiitake (Lentinula edodes), button (Agaricus bisporus) and oyster (Pleurotus ostreatus) mushrooms are known for their bioactive properties. The application of ultraviolet (UV) irradiation for the production of substantial amounts of vitamin D2 is well established. Levels of serum 25-hydroxy vitamin D (25-OHD), parathyroid hormone (PTH), calcium, phosphorus and alkaline phosphatase (ALP) were significantly (p < 0.05) improved in vitamin-D-deficient rats after feeding with UVB irradiated mushrooms for 4 weeks. Further, microscopic observations indicate an improvement in the osteoid area and the reduction in trabecular separation of the femur bone. In addition, the level of expression of the vitamin D receptor (VDR) gene and genes metabolizing vitamin D were explored. It was observed that in mushroom-fed and vitamin-D-supplemented groups, there was upregulation of CYP2R1 and VDR, while there was downregulation of CYP27B1 in the liver. Further, CYP2R1 was downregulated, while CYP27B1 and VDR were upregulated in kidney tissue.

Association of 25-hydroxyvitamin D status with brain volume changes

Vitamin D is critical to brain function and its deficiency accelerates cognitive impairment. There is limited understanding of the brain-specific areas that undergo volume change in relation to blood vitamin D levels. The objective of this study was to evaluate the association between blood 25-hydroxyvitamin D (25(OH)D) concentration and structural changes in the brain. We analyzed structural three-dimensional T1 MRI images of 201 elderly individuals (mean age = 74.91 ± 9.21 years; 68.1% female; mean 25(OH)D = 18.05 nmol/L), with 10 community-based normal healthy subjects, 33 with subjective cognitive decline, 97 with mild cognitive impairment, and 61 with Alzheimer's disease (AD). To analyze the structural changes in the brain respective to blood 25(OH)D, multiple regression analyses were performed using voxel-based morphometry with age and total intracranial volume as covariates. Lower 25(OH)D level were associated with reduced brain volume in right olfactory, rectus GM regions (FWE-corr, p < .05) for entire subjects. For AD subjects, left parahippocampal, fusiform, and hippocampal areas were positively associated with 25(OH)D (FWE-corr, p < .05). Low blood 25(OH)D was associated with reduced volumes in olfactory and hippocampal regions in elderly patients with cognitive decline. Our results may provide insight into the neurological pathophysiology of vitamin D.

Evaluation of the analytical performance of the Beckman Coulter Unicel DXI 800 Access Total 25(OH) Vitamin D immunoassay

Background

As vitamin D has recently been implicated in various diseases, vitamin D testing has gained a lot more significance. Vitamin D deficiency is quite prevalent, and detection of this condition is important. Several manufacturers have developed new automated immunoassays for this purpose. In this study, we aimed to evaluate the analytical performance of the Access Total 25(OH) Vitamin D immunoassay on the Beckman Coulter Unicel DXI 800 analyzer, through comparison with the reference method, liquid chromatography/tandem mass spectrometry (LC-MS/MS).

Methods

The study was conducted with 148 patient samples which were sent to Ankara Numune Training and Research Hospital for routine vitamin D testing. Every sample was analyzed with both Unicel DXI 800 immunoassay analyzer and LC-MS/MS. The concordance of the results was evaluated with Passing-Bablok regression analysis and Bland-Altman plot. Additionally, imprecision, interference, limit of blank (LOB), recovery, linearity and carry-over studies were performed for the Beckman Coulter Unicel DXI 800 analyzer.

Results

When compared to LC-MS/MS, the Access Total 25(OH) Vitamin D immunoassay on the Beckman Coulter Unicel DXI 800 analyzer had an R-value of 0.957 (intercept: −3.938, slope: 1.185) and a mean bias of 9.5%. The concordance correlation coefficient (CCC) between the two methods was 0.916. The intra-assay, inter-assay and total coefficient of variation (CV%) for the Unicel DXI 800 vitamin D immunoassay were 3.3%, 5.3% and 8.3%, respectively, at 31.7 ng/mL concentration, and 2.1%, 3.2% and 7%, respectively, at 66.8 ng/mL concentration.

Conclusions

The Access Total 25(OH) Vitamin D immunoassay method has acceptable analytical performance, and the results are in concordance with the LC-MS/MS results.

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.

Correlation between tear fluid and serum vitamin D levels

Background

Vitamin D deficiency is associated with a range of systemic diseases including ocular disorders. The objective of this study is to measure tear vitamin D levels and investigate the correlation between serum and tear vitamin D levels.

Methods

A total of 48 healthy volunteers without any systemic and ocular disease were recruited for this observational cohort study. Serum was collected using clot activator coated Vacutainer® Plus tubes. Tear fluid was collected using Schirmer’s strips. Serum and tear total 25-hydroxyvitamin D levels were measured by competitive chemiluminescent ELISA and the correlation between the levels were studied.

Results

The measured serum 25-hydroxyvitamin D level ranged between 3.3 and 27.5 ng/ml (Mean ± SEM, 9.4 ± 0.7 ng/ml; Median 8.4 ng/ml). Significantly (p < 0.0001) higher level of 25-hydroxyvitamin D was detected in the tears (Mean ± SEM, 17.0 ± 1.6 ng/ml; Range 3.2–45.8 ng/ml; Median, 16.3 ng/ml) compared to serum. An average of ~2 fold (Mean ± SEM, 1.9 ± 0.2; Range 0.4–5.8; Median, 1.7) higher 25-hydroxyvitamin D was observed in tears compared to serum in the subjects. In addition, a positive correlation was observed between serum and tear 25-hydroxyvitamin D levels (r = 0.5595; p < 0.0001).

Conclusions

A higher level of 25-hydroxyvitamin D was observed in the tear fluid compared to that of the serum. It would be beneficial to consider tear vitamin D levels to study its role with reference to ocular surface diseases.

Evaluation of the analytical performance of Unicel DXI 800 for the Total 25 (OH) Vitamin D measurements

OBJECTIVES

We assessed the analytical performance of newly developed Access 25(OH) Vitamin D Total assay with Beckman Coulter Unicel DXI 800 and evaluated the agreement between a reference method liquid chromatography/tandem mass spectrometry (LC-MS/MS) and a chemiluminescence method (LIAISON, DiaSorin).

DESIGN AND METHODS

160 serum samples were included. Deming Regression analysis and Bland-Altman plots were used. The concordance correlation coefficient (CCC) was used to assess the degree of agreement between assays and the reference method.

RESULTS

The CV% values of Unicel DXI 800 for within-run, between-run and between-day were lower than 6%. When compared to LC-MS/MS, the Access 25(OH) Vitamin D Total assay demonstrated an R value of 0.9444 (intercept -0.089, slope 0.951), with an average bias of -2.9%, and the LIAISON 25(OH) Vitamin D Total assay an R value of 0.9405 (intercept -0605, slope 0.924), with an average bias of -13.6%. In comparison with the LIAISON 25(OH) Vitamin D Total assay, the Access 25(OH) Vitamin D Total assay demonstrated an R value of 0.9498 (intercept 0.528, slope 1.029), with an average bias of 1.2%. The agreement with the LC-MS/MS method, based on values of the CCC, was moderate for the Unicel DXI 800 and LIAISON method (0.95, 0.94 respectively).

CONCLUSIONS

The new, automated Access 25(OH) Vitamin D Total assay showed an acceptable correlation with LC-MS/MS and LIAISON. Both methods moderately achieved to classify the patients according to their vitamin D status. However, we need further standardization of vitamin D assays to enhance the accuracy and comparability.

Multicenter Comparison of Seven 25OH Vitamin D Automated Immunoassays

BACKGROUND

The measurement of 25OH vitamin D continues to grow in clinical laboratories. The aim of this multi-center study was to compare the results of seven automated commercial immunoassays with a reference HPLC technique.

METHODS

One hundred and twenty consecutive outpatient serum samples were centrifuged, divided in aliquots, frozen and shipped to the participating laboratories. 25OH Vitamin D was measured with a reference HPLC system and with seven automated commercial immunoassays (Roche Cobas E601, Beckman Coulter Unicel DXI 800, Ortho Vitros ES, DiaSorin Liaison, Siemens Advia Centaur, Abbott Architect i System and IDS iSYS).

RESULTS

Compared to the reference method, the regression coefficients ranged from 0.923 to 0.961 (all p<0.001). The slope of Deming fit ranged from 0.95 to 1.06, whereas the intercept was comprised between -15.2 and 9.2 nmol/L. The bias from the reference HPLC technique varied from -14.5 to 8.7 nmol/L. The minimum performance goal for bias was slightly exceeded by only one immunoassay. The agreement between HPLC and the different immunoassays at 50 nmol/L 25OH Vitamin D varied between 0.61 and 0.85 (all p<0.001). The percentage of samples below this cut-off was significantly different with only one immunoassay.

CONCLUSIONS

The excellent correlation with the reference HPLC technique attests that all seven automated immunoassays may be reliably used for routine assessment of 25OH-D in clinical laboratories. The significant bias among the different methods seems mostly attributable to the lack of standardization and calls for additional efforts for improving harmonization of 25OH-D immunoassays.

Analysis of vitamin D status at two academic medical centers and a national reference laboratory: result patterns vary by age, gender, season, and patient location

BACKGROUND

Testing for 25-hydroxyvitamin D [25(OH)D] has increased dramatically in recent years. The present report compares overall utilization and results for 25(OH)D orders at two academic medical centers - one in New York and one in Iowa - in order to characterize the vitamin D status of our inpatient and outpatient populations. Results are also compared to those from a national reference laboratory to determine whether patterns at these two institutions reflect those observed nationally.

METHODS

Retrospective data queries of 25(OH)D orders and results were conducted using the laboratory information systems at Weill Cornell Medical College / New York Presbyterian Hospital (WCMC), University of Iowa Hospitals and Clinics (UIHC), and ARUP Laboratories (ARUP). Chart review was conducted for cases with very high or low serum 25(OH)D levels in the WCMC and UIHC datasets.

RESULTS

The majority of tests were ordered on females and outpatients. Average serum 25(OH)D levels were higher in female versus male patients across most ages in the WCMC, UIHC, and ARUP datasets. As expected, average serum 25(OH)D levels were higher in outpatients than inpatients. Serum 25(OH)D levels showed seasonal periodicity, with average levels higher in summer than winter and correlating to regional UV index. Area plots demonstrated a peak of increased 25(OH)D insufficiency / deficiency in adolescent females, although overall worse 25(OH)D status was found in male versus female patients in the WCMC, UIHC, and ARUP datasets. Surprisingly, improved 25(OH)D status was observed in patients starting near age 50. Finally, chart review of WCMC and UIHC datasets revealed over-supplementation (especially of ≥ 50,000 IU weekly doses) in the rare cases of very high 25(OH)D levels. General nutritional deficiency and/or severe illness was found in most cases of severe 25(OH)D deficiency.

CONCLUSIONS

25(OH)D status of patients seen by healthcare providers varies according to age, gender, season, and patient location. Improved 25(OH)D status was observed later in life, a finding that may reflect the previously described increased use of vitamin D-containing supplements in such populations. Severe vitamin D deficiency is much more common than vitamin D toxicity.

Determination of vitamin D and its metabolites

The demand for analysis of 25-hydroxyvitamin D has increased dramatically throughout the world over the past decade. As a consequence, a number of new automated assays have been introduced for 25-hydroxyvitamin D measurement. Automated assays have shown variable ability to meet the technical challenges associated with 25-hydroxyvitamin D measurement. Assays are able to meet performance goals for precision at high concentrations but fail to do so at low concentrations of 25-hydroxyvitamin D. The overall accuracy of automated methods has improved over recent years and generally shows good overall agreement with reference methods; however, discrepancies persist for individual samples. Liquid chromatography-tandem mass spectrometry is used by some routine laboratories for 25-hydroxyvitamin D analysis but its widespread use is hampered by limited sample throughput. 1,25-Dihydroxyvitamin D is an important analyte in specific clinical situations, which remains in the hands of specialised laboratories using manual analytical methods.