Document Type : Methodological papers
Clinical Pathology Department, NCI, Cairo, Egypt.
Clinical Pathology Department, CCHE, Cairo, Egypt.
Personalized Medication Management Unit, Pharmacy, CCHE, Cairo, Egypt.
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.