去氧核醣核酸(DNA) 被體內或環境中具反應性物種修飾後會在DNA 複製時導致基因突變，為細胞癌化的第一步。因此將DNA 之修飾產物準確地定量可用來評估致癌的風險，進而發展預防癌症的策略。蛋白質因具反應性物種產生的後轉譯修飾，會因改變其結構而導致功能上的改變。本文介紹以各種質譜法分析生物體(組織與體液) 內超微量之被修飾後的DNA 與蛋白質作為疾病的生化指標之研究。

Modifications of DNA by endogenous or environmental reactive species could lead to mutation during DNA replication, which is the initiation step of carcinogenesis. Thus, accurate quantification of modified DNA products has been used for cancer risk assessment and for strategies in cancer prevention. Post-translational modifications of proteins by reactive species could cause functional alteration of proteins due to structural change. In this article, analyses of the ultra-trace amounts of the DNA and protein modification products by various mass spectrometric methods are reviewed.