Evaluation of Plasma Arginine Vasopressin During Hypertonic Saline Loading: A Comparison of Radioimmunoassay and Liquid Chromatography-Tandem Mass Spectrometry.

Abstract

Plasma arginine vasopressin (AVP) measurement is critical for diagnosing central diabetes insipidus (CDI). Conventional radioimmunoassay (RIA) is widely used for AVP quantification, but its limited sensitivity, specificity, and dynamic range have prompted exploration of alternative methods. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) has emerged as a promising technique for AVP measurement, offering potential advantages over RIA. This study aimed to evaluate LC-MS/MS performance for AVP quantification during hypertonic saline loading and compare its diagnostic accuracy with that of RIA in differentiating CDI patients from controls. A total of 335 plasma samples were collected from 77 individuals-23 diagnosed with CDI and 54 controls-during hypertonic saline loading. AVP concentrations were measured using both LC-MS/MS and RIA. Statistical analyses included Wilcoxon tests to compare AVP levels, correlation analysis between LC-MS/MS and RIA, and receiver operating characteristic (ROC) curve analysis to assess diagnostic performance. LC-MS/MS demonstrated a lower detection limit (0.3pg/mL) and a broader quantification range than RIA. Regression analysis showed a strong correlation between LC-MS/MS and RIA in the control group, but no correlation in the CDI group. ROC analysis indicated that LC-MS/MS provided diagnostic accuracy comparable to RIA for distinguishing CDI patients from controls. Bland-Altman analysis showed the agreement between two methods at the low range of AVP. LC-MS/MS offers equivalent specificity and sensitivity to RIA for AVP measurement, while providing added benefits in time efficiency, cost-effectiveness, and differential diagnosis of CDI. These findings suggest that LC-MS/MS is a viable alternative to RIA for clinical AVP quantification.