Diazyme's 25-OH Vitamin D Assay for Clinical Chemistry Analyzers
Diazyme's Enzyme-Immunoassay FemtoQuant™ 25-Hydroxy Vitamin D test is based on the principle of α-complementation of the enzyme β-galactosidase and the competition between an enzyme donor-25-OH Vitamin D conjugate, an anti-Vitamin D antibody and the 25-OH Vitamin D content of a serum sample. Samples with higher 25-OH Vitamin D concentrations produce higher β-galactosidase activities and vice versa. A nitrophenyl-ß- galactoside derivative (NPG) is used as the enzyme substrate. The reaction's product has maximum absorbance at 415 nm. The 25-OH Vitamin D concentration of a sample is proportional to the measured β-galactosidase activity.
Diazyme 25-OH Vitamin D for Clinical Chemistry Analyzers Kit Configuration:
Diazyme's Vitamin D assay kit contains 1 sample diluent and 3 liquid stable reagents and calibrator set. The intended use is for the quantitative determination of 25-(OH) D levels in serum or plasma, on automated chemistry analyzers, and for the assessment of Vitamin D sufficiency.
- Multiple instrument options available
- Reagent kit, calibrator and control sets offered separately
- Liquid Stable format
- Minimal sample of only 20 μL needed
- 15-19 minutes to first result
- Report total 25-OH Vitamin D (D2+D3)
- No off-line sample pretreatment needed
- Excellent Correlations to LC-MS/MS and leading 25-OH Vitamin D Immunoassays
- Cost effective
The assay procedure for the Roche Modular P chemistry analyzer is shown below: Specimen calibrator, control and samples are first diluted onboard: 20 μL of serum which is then diluted with 155 μL of diluent. Once diluted an additional 20 μL of the diluted specimen is then used for analysis.
The performance of this assay was compared to the performance of a legally marketed 25-OH Vitamin D enzyme immunoassay. The results for 98 serum samples are shown in the table below:
|Deming Regression Analysis||95% Confidence Interval|
|Slope||1.005 (0.969 to 1.041)|
|Intercept||-0.21 (-2.15 to 1.73)|
|Correlation Coefficient||0.984 (0.976 to 0.989)|
Eleven levels of linearity were prepared by diluting a high serum sample with Vita-min D-depleted serum. Linearity levels were prepared according to the CLSI EP6-A guideline. Measurements were done in triplicates. The assay was found to be linear between 7.6 and 147.8 ng/mL.
The assay demonstrated excellent correlations with results determined by LC-MS/MS and DiaSorin CLIA methods with R2 values of >0.95 and 0.96.
The LOB, LOD, and LOQ of Diazyme's 25-OH Vitamin D Assay for Clinical Chemistry were determined according to CLSI (formerly NCCLS) EP17-A guidelines. The assay's LOB = 2.0 ng/mL; LOD = 3.5 ng/mL; and LOQ = 7.6 ng/mL.