Effects of sample matrix in the measurement of antithrombin by LC-MS: A role for immunocapture.

The sample matrix composition, which is greatly affected by the type of blood collection tube used during phlebotomy, is of major importance in laboratory testing as it can influence test results. We developed an LC-MRM-MS test to molecularly characterize antithrombin in citrate plasma. The test principle differs greatly from traditional laboratory tests and the influence of varying plasma sample matrices is largely unknown. To identify whether variations in sample matrix affect the LC-MRM-MS test for antithrombin and assess whether sample pre-processing by immunocapture reduces matrix-specific effects. Samples (n = 45) originating from four different blood collection tubes (sodium citrate, lithium heparin, K Deming regression analysis of directly processed samples revealed slopes deviating >5% from the line of identity for at least six out of 22 peptides in all matrices. Significant differences between all matrices were found upon analysis by ANOVA for at least 10 peptides. Pre-processing by immunocapture led to slopes within 5% of the line of identity for nearly all peptides of the matrices. Furthermore, significant differences between matrices after immunocapture were only observed for four peptides. Variations in the sample matrix affect the measurement of antithrombin by LC-MRM-MS, but observed effects are greatly reduced upon pre-processing by immunocapture.

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The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.