Analytical evaluation of the BioPlex® 2200 25-OH vitamin D total assay.
BACKGROUND
Testing for 25-hydroxyvitamin D (25(OH)D) has increased dramatically over the past decade and several automated immunoassays exist to measure serum 25(OH)D. Here we assess the performance of the recently released automated Bio-Rad BioPlex® 2200 25-OH vitamin D immunoassay, claimed to equally detect 25(OH)D2 and 25(OH)D3, and compare its results against a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method and the well-established DiaSorin LIAISON® 25-OH vitamin D total immunoassay.


METHODS
Imprecision was determined using third party controls over 20days. Linearity over the claimed measuring range was assessed using admixtures of a high and a low patient pool. Correlation between the BioPlex and LC-MS/MS (n=137) or the LIAISON (n=56) was assessed using patient samples with varying amounts of 25(OH)D3 and/or 25(OH)D2.


RESULTS
The total imprecision was 9.4%, 6.9% and 4.5% at concentrations of 39.4nmol/L, 70.6nmol/L and 242.8nmol/L, respectively. The assay was linear from 33.1-375.0nmol/L with a R(2) of 0.993. Method comparison revealed a strong correlation between the BioPlex assay and LC-MS/MS for samples containing 25(OH)D2 alone (n=5; R(2)=0.999), 25(OH)D3 alone (n=119; R(2)=0.935) and both (n=13; R(2)=0.919). In samples tested by all three methods (n=56), the correlation between the BioPlex and the LIAISON (R(2)=0.853) was poorer than that of the BioPlex and LC-MS/MS (R(2)=0.942).


CONCLUSIONS
The BioPlex assay is suitable for the measurement of total serum 25(OH)D. The strong correlation between the BioPlex assay and LC-MS/MS in detecting 25(OH)D2 and 25(OH)D3 provides evidence that the BioPlex assay is capable of the equivalent detection of both forms.
Department of Clinical Biochemistry, University Health Network, Toronto, ON, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada; Clinical Chemistry Division, Provincial Laboratory Services, Queen Elizabeth Hospital, Charlottetown, Prince Edward Island, Canada; Department of Pathology, Faculty of Medicine, Dalhousie University, Halifax, NS, Canada.
Mohamed
M
Abou El Hassan
Department of Clinical Biochemistry, University Health Network, Toronto, ON, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada.
Dan C C
DCC
Lin
Department of Clinical Biochemistry, University Health Network, Toronto, ON, Canada.
Tammy
T
Earle
Department of Clinical Biochemistry, University Health Network, Toronto, ON, Canada.
Megan
M
Spencer
Department of Clinical Biochemistry, University Health Network, Toronto, ON, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada. Electronic address: ivan.blasutig@uhn.ca.
Ivan M
IM
Blasutig
D015652:25-Hydroxyvitamin D 2 / Q000097:blood*; D015415:Biomarkers / Q000097:blood*; D002112:Calcifediol / Q000097:blood*; D002853:Chromatography, Liquid / Q000379:methods*; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D011108:Polymers / Q000737:chemistry*; D015203:Reproducibility of Results; D053719:Tandem Mass Spectrometry / Q000379:methods*
D015415:Biomarkers; D011108:Polymers; D015652:25-Hydroxyvitamin D 2; C004216:bioplex; D002112:Calcifediol
25-Hydroxyvitamin D; BioPlex; LC–MS/MS; Method comparison; Vitamin D