Elevated urine arsenic: un-speciated results lead to unnecessary concern and further evaluations

The consumption of seafood within two to three days of testing can increase total urine arsenic concentrations. Few clinicians are familiar with this fact and often misinterpret elevated results. A retrospective chart review of all cases with arsenic testing seen between 1991 and 2004 at an occupational and environmental medicine referral clinic was performed. Urine arsenic results were classified as follows: total arsenic levels; speciated results (inorganic, ionic arsenic); and whether the patient abstained from seafood prior to the collection. Laboratory detection limits for total and for ionic arsenic were < or = 2 microg/L. Fifty-four patients with urine arsenic testing were identified. The total urine arsenic concentration exceeded 40 microg/L for 28 patients. On paired, speciated testing (n = 21), mean total arsenic was 122 +/- 227 microg/L, and ionic arsenic was not detected in any of these same samples (p = 0.023). On paired testing, before and after seafood abstention (n = 12), total urine arsenic without abstention was 291 +/- 267 microg/L, and it was only 9 +/- 12 microg/L after seafood abstention (p = 0.004). The total urine arsenic elevations observed in our series were due to benign organic arsenic compounds commonly found in seafood. Laboratories should reflexively perform speciation on most samples with elevated total arsenic concentrations prior to reporting the results. Reflexive speciation could reduce unnecessary referrals, further testing, and patient anxiety.