Ignazia Carlisi

Analytical and clinical validation of the new Abbot Architect 25(OH)D assay: fit for purpose?

Abstract Background: We provide a clinical and analytical evaluation of the reformulated version of the Abbott Architect 25-hydroxyvitamin D assay. We compared this assay with three commercial automated immunoassays and against a VDSP-traceable liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) in six different populations. We also supplemented 40 healthy volunteers with either 600,000 IU of vitamin D2 or 100,000 of vitamin D3 to evaluate the performance of the immunoassays vs. the LC-MS/MS. Methods: Precision and limit of quantification were assessed, 25(OH)D2 and C3-epimer recovery were calculated. Two hundred and forty samples obtained in healthy Caucasians and Africans, osteoporotic, hemodialyzed and intensive care patients and 3rd trimester pregnant women were analyzed by all methods. Correlation was studied using Passing-Bablok and Bland-Altman analysis. Concordance correlation coefficient (CCC) was calculated to evaluate agreement between immunoassays and LC-MS/MS. We verified if patients were homogeneously classified with the immunoassays when they took vitamin D2 or vitamin D3 after 1, 7 and 28 days. Results: We observed excellent analytical features and showed a very good correlation to the LC-MS/MS results in the overall population. Compared to the other immunoassays, concordance of the new Abbott assay with the LC-MS/MS was at least similar, and often better in diseased populations. Althought the cross-reactivity with 25(OH)D2 was not of 100%, there was no significant difference in the classifications of the patients, either supplemented with D2 or D3 or after 7 or 28 days. Conclusions: This modified version of the Abbott Architect assay is clearly improved compared to the previous one and presents a better agreement with the LC-MS/MS.

Technical and clinical evaluation of the VITROS® Immunodiagnostic Products 25-OH Vitamin D Total Assay--comparison with marketed automated immunoassays and a liquid chromatography-tandem mass spectrometry method.

Abstract Background: The study was conducted to evaluate the technical and clinical performance of the VITROS® Immunodiagnostic Products 25-OH Vitamin D Total Assay, and compare it with the performance of five marketed automated assays and a liquid chromatography/mass spectrometry reference method (LC-MS/MS). Methods: Three hundred patient serum samples were used to compare the correlation of the VITROS® 25-OH Vitamin D Total Assay with both the other immunoassays and the LC-MS/MS method, using Passing-Bablok regression and Bland-Altman analyses. Concordance of the diagnosis of vitamin D status was calculated to test the agreement between the different assays. In addition, samples containing vitamin D2 were used to test the assay’s ability to detect the D2 form of the vitamin. Results and conclusions: These results from the VITROS® 25-OH Vitamin D Total Assay generally correlated well with those from most of the marketed immunoassays. Cross-reactivity of the D2 form was calculated as being close to 100%. Additionally, we found substantial variability in performance amongst the various assays, which suggests the need for optimisation and recalibration of commercial methods.