Total arsenic screening prior to fractionation enhances clinical utility and test utilization in the assessment of arsenic toxicity

The objective was to evaluate the utility of a screen with reflex-to-fractionation testing compared with direct-to-fractionation testing for suspected toxic exposure. This study was based on a retrospective data analysis of urine arsenic results from previously tested samples (n=12,960). Total urine arsenic by inductively coupled plasma mass spectrometry was used as a screening method to identify elevated arsenic concentrations. Arsenic fractionation was the speciation assay to differentiate toxic and benign arsenic species. Screening samples based on total arsenic concentration resulted in less than 10% of samples requiring arsenic fractionation, with a final positivity rate of less than 1% for toxic arsenic. Samples with fractionation ordered directly had a positivity rate for toxic arsenic of 3.3%. The overall positivity rate for exposure to toxic arsenic was less than 1%. A total arsenic screen before fractionation reduces the number of samples requiring fractionation by more than 91%, supporting the use of a screen with a reflex-to-fractionation approach for urine arsenic.