Development of a sensitive liquid chromatography-tandem mass spectrometry method for quantification of human plasma arginine vasopressin.

Abstract Background and aims Direct measurement of arginine vasopressin (AVP) via immunoassays is not widely conducted, mainly because of technical constraints. Liquid chromatography–tandem mass spectrometry (LC/MS/MS) has been widely used as the gold standard in clinical chemistry. Here, we aimed to develop an MS-based assay to determine human plasma AVP and compare the results with those obtained using a conventional immunoassay. Materials and methods We developed a protocol using triple quadrupole MS coupled with LC for the measurement of human plasma AVP. Analytical evaluations of the method were performed, and the results obtained using LC/MS/MS and radioimmunoassay (RIA) were compared. Results The lower limit of quantification (LLOQ) for plasma AVP obtained using LC/MS/MS and RIA were 0.2 and 0.4 pg/mL, respectively. Although there was a weak overall correlation between the results obtained using the two different methods, the RIA results did not agree with the LC/MS/MS results, particularly at low concentrations. Conclusions AVP detection through RIA is not satisfactory compared with that using LC/MS/MS. Diagnostic values of direct AVP measurements must be evaluated based on the results obtained via sensitive and accurate MS-based methods rather than those obtained through RIA.