利用總砷定量篩檢提升砷分類評估砷暴露之臨床效益

Total Arsenic Screening Prior to Arsenic Speciation Enhances Clinical Utility in the Assessment of Arsenic Exposure

尿中砷的濃度可作為近期砷曝露的指標，勞工若暴露在無機砷工作環境中，須定期監控尿中砷以預防職業病產生。若以尿液總砷含量來評估砷暴露會受到食品有機砷影響，需用砷分類檢測將無機砷及有機砷分離。美國政府工業衛生技師協會（ACGIH）訂定無機砷生物暴露指標為無機砷及其代謝物總量不可大於35μg/L，但砷分類檢測成本高，本研究探討若以尿液總砷含量為初步篩檢，濃度要多高才需要進行砷分類檢驗，以期有效降低砷分類所需的龐大成本。收集120支不同濃度總砷檢驗的檢體（19.8~496.3μg/L）進行砷分類檢測，比較總砷及砷分類後加總結果，相關係數（r2）為0.94，兩者呈正相關，證明尿總砷適合作為評估砷暴露的初步篩檢。總砷小於60μg/L的檢體中，無機砷濃度全部小於35μg/L，證明尿總砷60μg/L可以為初步篩檢標準。根據本院民眾健康檢查共15,911件總砷測量結果，推估4,928件檢體（31.0%）以尿總砷檢測就可排除砷暴露風險。勞動部已將尿中無機砷檢驗納入勞保職業病健檢，若能利用尿總砷進行篩檢，可提升無機砷檢測效益，有效利用醫療資源。

Urinary arsenic is a good biomarker for recent exposure to arsenic, but total arsenic is difficult to confirm the presence of toxic forms. Fractionation methods are essential for monitoring toxic arsenic exposure. However, it is not efficient and cost-effective to perform arsenic fractionation for all suspected toxic exposure. The study was to find an appropriate cutoff value for a total arsenic screening reflex to fractionation in the assessment of arsenic toxicity. American Conference of Governmental Industrial Hygienists (ACGIH) provided an occupational biological effect index for urinary inorganic arsenic plus metabolites of 35 μg/L. Clinically positive sample is defined as the sum of inorganic arsenic and metabolites higher than 35 μg/L. Of the total 120 urine samples, 35 samples with total arsenic results less than 60 μg/L are 100% clinically negative. We retrospectively analyzed arsenic results from previous tested 15,911 samples over the past three years by using 60 μg/L as a determinant and found 4,928 samples can be ruled out the risk of arsenic poisoning by total arsenic analysis. A urinary total arsenic screen prior to arsenic fractionation is highly recommended in assessment of arsenic toxicity and can reduce 31% of samples requiring fractionation assay.