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Measuring serum 25-hydroxyvitamin D is key in clinical labs, but inter-laboratory variations risk diagnostic errors. This study evaluates the performance of current in-house liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods used in top Chinese clinical laboratories and proposes an optimized method for improving serum 25(OH)D measurement accuracy and reliability.Seven serum pools with different concentrations of 25(OH)D were prepared and sent to 12 participating laboratories for multiple repeat analysis with their current in-house LC-MS/MS methods and then an optimized LC-MS/MS method. Precision was assessed in terms of coefficient of variance (CV), and trueness was assessed in terms of bias referring to the U.S. National Institute of Standards and Technology (NIST) reference measurement procedure (RMP). The analytical performances of the two methods were compared and evaluated.Eighty percent and 90 % of the laboratories achieved the defined performance criteria (CV, <12.5 %; mean bias, <8.3 %) with the optimized method for the measurement of 25(OH)D2 and 25(OH)D3, compared with 43 % and 57 % of the laboratories meeting the criteria with their in-house methods, respectively. Precision and trueness improved after applying the optimized method. Although the optimized method didn’t not ensure that all laboratory samples meet the measurement uncertainty (MU) criteria (MU<13.6 %), particularly for low-concentration samples, it significantly reduced the MU compared to the in-house method.Precision, trueness and MU improved after applying the optimized method. Nonetheless, more efforts are needed to ensure the reliability and accuracy of 25(OH)D measurements in clinical laboratories in China. [ABSTRACT FROM AUTHOR] more...

Monoclonal immunoglobulins can cause interference in many laboratory analyses. During a 4 month period we observed seven patients with monoclonal disease and falsely extremely elevated 25-hydroxyvitamin D (25(OH)D) results above 160 ng/mL (>400 nmol/L) measured using an immunoassay from Abbott Diagnostics. Based on these findings, we studied the occurrence of falsely elevated 25(OH)D in samples with paraproteins and investigated possible mechanisms of the observed interference. 25(OH)D was analyzed using the Architect i2000 platform from Abbott Diagnostics and a higher order method, liquid chromatography-mass spectrometry (LC-MS/MS), in serum samples from 50 patients with known monoclonal disease. Patients with falsely elevated 25(OH)D were included in further studies to elucidate the cause of interference. Spuriously elevated results were in addition analyzed on two alternative platforms (Siemens and Roche). Falsely elevated 25(OH)D levels were present in eight patients on the Abbott analyzer and one on the Siemens platform. Results from Roche were comparable with LC-MS/MS. Additional investigations excluded elevated concentrations of rheumatoid factor and heterophilic antibodies as the cause of interference in the Abbott assay. Laboratories should be aware of the risk of falsely elevated 25(OH)D in samples run on the Architect analyzer from patients with monoclonal disease. Highly elevated vitamin D results should be diluted and if the dilution is non-linear, rerun by a different method, preferably LC-MS/MS. In patients with spuriously elevated 25(OH)D without known monoclonal disease, the laboratory should consider requesting protein electrophoresis to exclude paraprotein interference. [ABSTRACT FROM AUTHOR] more...

Background/objectives: To assess vitamin D status during normal pregnancy and in the postpartum lactation period. Subjects/methods: The study comprised 141 healthy, ethnic Danish women with normal pregnancies, who were residents in Greater Copenhagen. Serum 25-hydroxy-vitamin D2+D3(25-OH-vitamin D) was measured at 18, 32 and 39 weeks' gestation and 8 weeks postpartum. Results: There was a significant increase in 25-OH-vitamin D from 18 to 32 weeks' gestation (P=0.0001) followed by a significant decrease from 32 to 39 weeks (P=0.001) as well as from 39 weeks to 8 weeks postpartum (P<0.0001). At 18, 32, 39 weeks' gestation and 8 weeks postpartum, median 25-OH-vitamin D values were 77, 98, 91, and 73 nmol/L, respectively. During pregnancy and postpartum, none of the women displayed severe vitamin D deficiency (values <13 nmol/L). Between 1.4% and 4.3% of the participants displayed moderate vitamin D deficiency (values 13-24 nmol/L), 16-19% displayed vitamin D insufficiency (values 25-50 nmol/L), 77-84% had values >50 nmol/L and 0.7-2.8% had values >200 nmol/L. Conclusions: Low vitamin D status is frequent among pregnant Danish women, especially in late pregnancy and during lactation. Median dietary intake of vitamin D in women of reproductive age was 2.4 μg/day (10-90 percentile range=1.4-5.0). The recommendations for vitamin D supplementation prior to conception, during pregnancy and lactation should be reconsidered. [ABSTRACT FROM AUTHOR] more...