| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Letters to the Editor |
1 ARUP Institute for Clinical, and Experimental Pathology, Salt Lake City, UT
2 Departments of Pathology, and Medicine, University of Utah, School of Medicine, Salt Lake City, UT
aAddress correspondence to this author at: ARUP Institute for Clinical and Experimental Pathology, LLC, 500 Chipeta Way, Salt Lake City, UT 84108.
To the Editor:
Vitamin D [ergocalciferol (D2) and cholocalciferol (D3)] is 25-hydroxylated by the liver and subsequently hydroxylated by the kidney to form 1,25-vitamin D, the active form of the vitamin. 25-Hydroxyvitamin D (25-OH-vitamin D) and 1,25-dihydroxyvitamin D have important effects on calcium absorption, bone calcium balance, and renal excretion of calcium and phosphorus (1). Assessment of the monohydroxy form of vitamin D is important for identifying insufficient endogenous synthesis disorders that impair gastrointestinal absorption and to identify renal or hepatic abnormalities (2).
Here we report on 25-OH-vitamin D as measured by the Nichols ADVANTAGE® 25-OH Vitamin D, DiaSorin LIAISON® 25-OH Vitamin D, DiaSorin 25-OH Vitamin D RIA, and liquid chromatography–tandem mass spectrometry (LC-MS/MS; Mayo Clinic). For measurement of vitamin D, the Nichols ADVANTAGE and DiaSorin LIAISON use a 2-site chemiluminescence assay; however, one important difference is that the Nichols ADVANTAGE relies on binding of vitamin D to a vitamin-D–binding protein purified from human sources and the DiaSorin LIAISON uses an antibody against 25-OH-vitamin D.
Problems have emerged with the Nichols ADVANTAGE 25-OH Vitamin D method. In patients supplemented with ergocalciferol (D2) to improve their vitamin D concentrations, the Nichols ADVANTAGE failed to consistently show the expected increase in vitamin D (3). Ergocalciferol (Drisdol; Sanofi Pharmaceutical) is the only vitamin D2 pharmaceutical preparation available for physicians in the United States to use as a vitamin D supplement; it is extracted from plants or fungi and is processed in the body to 25-OH-vitamin D2 and 1,25-dihydroxyvitamin D2. The DiaSorin LIAISON was shown not to underestimate the D2 concentration (4).
To further analyze the various methods, we measured vitamin D from 110 deidentified samples (Institutional Review Board no. 7740), using the Nichols ADVANTAGE, DiaSorin LIAISON, and a manual DiaSorin RIA. Vitamin D measured by the Nichols ADVANTAGE and DiaSorin LIAISON gave a Deming (5) regression of y = 1.04x – 4.20 µg/L (Fig. 1
). The DiaSorin RIA vs the Nichols ADVANTAGE gave a Deming regression of y =1.42x – 8.39 µg/L, and the DiaSorin RIA vs the DiaSorin LIAISON gave y = 1.37x – 9.64 µg/L.
|
Eight samples with significant variation in vitamin D values between the Nichols ADVANTAGE and the DiaSorin LIAISON were measured by LC-MS/MS. Deming results were y = 0.36x + 14.23 µg/L for LC-MS/MS vs the Nichols ADVANTAGE; y = 1.22x – 2.97 µg/L for LC-MS/MS vs the DiaSorin LIAISON; and y = 0.76x – 8.96 µg/L for LC-MS/MS vs the DiaSorin RIA.
For 3 of the samples, the Nichols ADVANTAGE yielded values <40% of those obtained by LC-MS/MS. Although the LIAISON gave slightly higher values than LC-MS/MS, there was good agreement with LC-MS/MS for those 8 samples. For patients using Drisdol to increase the absorbance of vitamin D, it is important that the physician be able to use an appropriate measurement system. Thus, we conclude that although there are differences between the assay results for most sera measured, the DiaSorin LIAISON should produce clinical agreement when used for diagnostic purposes for patients treated with vitamin D2.
References
The following articles in journals at HighWire Press have cited this article:
|
|
 |
|
  G. L. Lensmeyer, D. A. Wiebe, N. Binkley, and M. K. Drezner HPLC Method for 25-Hydroxyvitamin D Measurement: Comparison with Contemporary Assays Clin. Chem., June 1, 2006; 52(6): 1120 - 1126. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
