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

OBJECTIVES: 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.

METHODS: 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.

RESULTS: 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%.

CONCLUSIONS: 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.