A Comparison between Three Different Automated Total 25-hydroxyvitamin D Immunoassay Methods and Ultra Performance Liquid Chromatography

Document Type : Methodological papers


1 Clinical Pathology Department, NCI, Cairo, Egypt.

2 Clinical Pathology Department, CCHE, Cairo, Egypt.

3 Personalized Medication Management Unit, Pharmacy, CCHE, Cairo, Egypt.

4 Clinical Research Specialist, Clinical Research Department, Epidemiology and Bio-statistics Unit, CCHE, Cairo, Egypt.


Objective: Vitamin D is a fat soluble vitamin responsible for calcium metabolism and more recently discovered effects. This led to an increase in requests for vitamin D test by clinicians. New automated assays have been introduced for 25-hydroxyvitamin D measurement. Methods: Results from these new method have to be related to a Standard method to obtain best results for practical usage. In our study, one hundred venous blood samples were analyzed for 25-OH vitamin D on three immunological methods in our lab and correlated with ultra-performance liquid chromatography (UPLC) method as a reference method. Results: Statistically analysis of results obtained for correlations between the 3 methods against the reference UPLC was done by Spearman’s Correlation. It showed positive correlation in all methods with significant p value < 0.001. Differences and biases between methods were evaluated using a Bland-Altman plot and Cohen’s Kappa agreement. Best agreement was found in Cobas 6000 followed by the Access2 then comes Architect.  Conclusions: All immunoassays can be used in routine 25(OH) D measurements, still some methods are better than others. A clinical laboratory must at least be aware of its method to avoid misinterpretation of results.


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