Whole blood selenium determination by inductively coupled plasma mass spectrometry

To develop a sensitive method for accurately measuring whole blood selenium and determining an appropriate reference interval for the local Cleveland population.

The assay was developed and validated on an inductively coupled plasma mass spectrometry (ICP-MS) with a collision cell. Whole blood trace element free EDTA tubes were used to collect samples for the reference interval study (n=50). Samples were collected after at least 8h fast from healthy adults (76% females) with ages between 19 and 64yr. Whole blood aliquots (1mL) in acid washed cryogenic vials were stored at -70°C until analysis.

The method passed the matrix effect, interference (except for Gd), and carryover tests. The method had a linear range of 0.2-7.1μmol/L with accuracies of 87.1-118.1%. The total assay imprecision (CV) was <2.5% across the concentration levels tested. Comparison to another ICP-MS assay offered by an independent clinical lab yielded a Deming regression with a slope of 0.98, an intercept of 0.1μmol/L, a standard error of estimate of 0.1μmol/L, a correlation coefficient of 0.9846, and an average difference of 0.8%. The whole blood Se reference interval using a transformed parametric method was 2.2-3.5μmol/L.

This whole blood Se ICP-MS methodology is sensitive and acceptable for patient testing.