Diapositive 1

1
SA 490
Automated Measurement of Total 25 Vitamin D on
the IDS-iSYS System
E. Cavalier, A.Carlisi, AC. Bekaert, JP. Chapelle
Department of Clinical Chemistry, University of
Liège, CHU Sart-Tilman, Liège, Belgium
Introduction Most health professionals know
vitamin D for its critical role in increasing the
efficiency of dietary calcium absorption and
preventing rickets in children. In the past
decade, emerging research has also uncovered
other important relationships between vitamin D
and bone health as well as new information
indicating it could potentially play a
significant role in strengthening the bodys
defenses against chronic and autoimmune diseases
and in controlling the growth of cells (both
normal and cancerous). These new evidences have
fuelled the global demand for 25-OH D testing.
Clinical laboratories are under pressured to seek
automated reliable platforms for 25-OH D analysis
to keep up with the demanded volume.
Immunodiagnostics System (IDS) has commercialized
a direct, fully automated, co-specific
immunoassay for 25-OH D for use on the IDS-iSYS
system. We seek to assess the analytical
performance of the IDS-iSYS 25-OH D assay, and to
compare this method to LC-MS/MS, DiaSorin
Liaison, and DiaSorin RIA methods. Methods We
determined the repeatability and reproducibility
on 6 pools, ranging from 6.2 ng/mL to 71.2 ng/mL,
the limit of quantification (LoQ) and the
accuracy profile of the IDS-iSYS 25-OH D method.
A total of 88 samples, selected to represent a
wide range of 25-OH D concentrations
5.6-85.6ng/mL, was assayed by each method.
Results Intra and inter-assay coefficients of
variation (CV) were lt11 at 6.2 ng/mL and lt8 at
71.25 ng/mL. The LoQ was established at 6.2
ng/mL. The accuracy profile between 6.2 and
71.2ng/mL showed that the risk that one result
falls out of the 30 acceptance limit is lt5,
indicating that the method is completely
validated in this range. The actual assay working
range is 5 to 140ng/mL. A comparison of IDS-iSYS
25-OH D with LC-MS/MS yielded the Passing Bablok
fit equation IDS-iSYS 1.03 x (LC-MS/MS)
1.50. The corresponding equation with Liaison
was IDS-iSYS 0.94 x (Liaison) 2.41, and with
RIA IDS-iSYS 1.00 x (RIA) 0.62.
Mean of the pools (ng/mL) Calculated ß-expectation tolerance limits (ng/mL) Risk to fall of the limits ()
6.240 4.721 , 7.759 1.982
9.590 7.104 , 12.08 2.879
15.57 13.39 , 17.75 0.1948
28.15 20.79 , 35.50 3.235
39.22 31.81 , 46.63 1.023
71.25 55.11 , 87.39 1.928
Conclusion The IDS-iSYS 25-OH D is a robust
method, presenting analytical performances in
accordance with the clinical expectations. The
IDS-iSYS 25-OH D values were in excellent
agreement with those determined with LC-MS/MS,
DiaSorin Liaison and DiaSorin RIA. This method
demonstrated suitable characteristics as a high
throughput, fully automated, co-specific 25-OH D
assay for clinical laboratories.