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      Falsely Elevated 25-Hydroxy-Vitamin D Levels in Patients with Hypercalcemia

      case-report
      1 , , 1 , 2
      Case Reports in Endocrinology
      Hindawi

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          Abstract

          Symptomatic hypercalcemia is a commonly encountered clinical scenario. Though it is important to collect detailed history to find clinical clues connecting to the etiology of hypercalcemia, the diagnostic workup of hypercalcemia depends heavily on laboratory analysis. Accurate measurement of the parathyroid hormone and vitamin D levels is essential. However, commercial laboratory measurement of vitamin D levels can be erroneous in the setting of abundant paraprotein in the serum. One of the most common conditions that can cause an increased amount of paraproteins is multiple myeloma. We report 2 cases of falsely elevated 25-hydroxy-vitamin D levels in patients presenting with hypercalcemia and an underlying diagnosis of MM.

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          Most cited references4

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          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. Copyright © 2013 Elsevier Ltd. All rights reserved.
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            Artefactual 25-OH vitamin D concentration in multiple myeloma.

            The most commonly used techniques to measure vitamin D are automated immunoassays which are known to be affected by interferences, especially from immunoglobulins present in the patient's serum. We present a case of a patient with myeloma in whom interference with the vitamin D assay was identified. An 83-year-old female, known to have IgG myeloma, was found to have a high concentration of 25-OH vitamin D on a routine test without any signs of vitamin D toxicity. She was not taking vitamin D supplements or any other multivitamin preparation and had minimal sun exposure. The initial and subsequent samples run by the ARCHITECT 25-OH vitamin D assay (chemiluminescent microparticle immunoassay technology, Abbott Laboratories, Abbott Park, IL) showed a high concentration of 25-OH vitamin D of 281 nmol/L and 327 nmol/L, respectively. Further fresh samples taken for 25-OH vitamin D and analysed by liquid chromatography-mass spectrometry (LC-MS/MS) and ARCHITECT analysis showed results of 49 nmol/L and 289 nmol/L, respectively. Our patient had high concentrations of circulating IgG paraproteins and had a long history of rheumatoid arthritis; paraproteins and rheumatoid factor may interfere in the assay. In conclusion, we report a case of a patient with IgG myeloma and rheumatoid arthritis with high concentrations of 25-OH vitamin D detected by the Abbott ARCHITECT, but not by a reference method (LC-MS/MS). The most likely cause of the discordant results is interference in the immunoassay by the paraprotein but interference from rheumatoid factor remains a possibility.
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              Erroneous laboratory results: what clinicians need to know.

              Laboratory tests such as 'conventional biochemistry' are analytically robust and trusted, however, some common tests performed by immunoassays, eg thyroid function tests, are inherently more prone to analytical interference, giving rise to incorrect results. Interfering antibodies capable of causing potentially misleading results in immunoassay varied from about 0.4% to 4%. Furthermore, this form of interference cannot be predicted a priori and cannot be detected even by most stringent laboratory quality control assurance schemes because it is unique to an individual sample. Since more than 10 million immunoassay tests are carried out yearly in the UK alone, the impact of this problem on delivering appropriate patient care can no longer be ignored. Clinicians tend to perceive all laboratory data in the same light. Because of this, increased awareness of the inherent limitations of these laboratory tests should trigger a more measured and thoughtful approach, thus ensuring patients receive appropriate investigations and treatment.
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                Author and article information

                Contributors
                Journal
                Case Rep Endocrinol
                Case Rep Endocrinol
                CRIE
                Case Reports in Endocrinology
                Hindawi
                2090-6501
                2090-651X
                2020
                9 August 2020
                : 2020
                Affiliations
                1Department of Internal Medicine, Einstein Medical Center Philadelphia, 5501 Old York Road, Philadelphia, PA 19141, USA
                2Department of Endocrinology, Einstein Endocrine Associates, 50 East Township Line Road Medical Arts Building, Suite G01, Elkins Park, PA 19027, USA
                Author notes

                Academic Editor: Osamu Isozaki

                Article
                10.1155/2020/8873506
                7431955
                790403e4-1850-4d08-9a33-1db191e7a0c0
                Copyright © 2020 Moon Kyung Choi et al.

                This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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                Case Report

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