Comparison of five automated 25OHD immunoassays and liquid chromatography tandem mass spectrometry method

Objective To compare the concordance of five automated 25OHD immunoassays with liquid chromatography tandem mass spectrometry method (LC-MS/MS). Methods During May to July in 2014, 245 clinical serum samples that requested 25OHD tests were selected, with a total 25OHD range of 2.8 ng/ml-64.0 ng/ml, in which 154 samples did not contain 25OHD2 and 91 samples contains both 25OHD2 and 25OHD3. To used a LC-MS/MS method that built in our laboratory to measure 25OHD, five commercial automated chemiluminescent immunoassays from Abbott Diagnostics(A), DiaSorin LIASON(B), IDS-iSYS(C), Roche Diagnostics(D), and Siemens ADVIA Centaur(E). Taking the reference method LC-MS/MS as a standard, to compared the concordance and performance of the five automated 25OHD immunoassays. And used the commonly accepted cutoffs for 25OHDdeficiency (<20 ng/ml), and insufficiency (20-30 ng/ml), and sufficiency (≥30 ng/ml)to compare the uniformity of different methods. Statistical analysiswere performed by MedCalc software, Passing & Bablok regression, Bland & Altaman plots and Box and whisker plots were performed to compare the differences of the methods. Results The medium (range: 2.5%-97.5%) 25OHD of the 245 serum samples of the six methods was 23.5(5.8-44.2) ng/ml(LC-MS/MS), 20.6 (7.1-43.5)ng/ml(A), 19.0 (5.4-38.0) ng/mL (B), 23.0 (10.0-38.1) ng/ml(C), 20.1 (5.1-46.0) ng/ml (D), 31.3 (12.3-71.1) ng/ml (E), respectively. Passing and Bablok regression showed that method B had the best correlation coefficient with LC-MS/MS (r=0.894), while methods A, C and D had relatively small bias compared withLC-MS/MS and method E had the large bias. If the serum samples did not contain 25OHD2, all the five automated immunoassays correlated well with LC-MS/MS with a correlation coefficient higher than 0.84, and B has the best correlation with LC-MS/MS (r=0.930). While all the correlation coefficient between immunoassays and LC-MS/MS decreasedwhen analyzing the samplescontaining 25OHD2. Using the clinical cutoffs, A, B, C, D and E had a concordance of 68.6%, 64.9%, 67.8%, 70.6% and 51.8% compared with LC-MS/MS, respectively. Conclusions There are significant differences between different detection systems of 25OHD.All the immunoassays results were affected by the existence of 25OHD2. The concordance of serum 25OHD resultswas poor between different methods, and it may be necessary to built exclusive cutoffs for different methods.(Chin J Lab Med, 2015, 38: 475-479) Key words: 25- hydroxyvitamin D2; Chromatography liquid; Tandem mass spectrometry