[Companion diagnostics: significances and issues in its clinical application].

Studies on the biological significance of human genome sequence variations revealed their association with diversity in patient's individual response to a particular drug. Based on it, pharmacogenomic tests have been developed and could be used as an indication of pharmacological responses to a therapeutic intervention to select appropriate patients to be treated with a particular drug, and adjust dosage to have maximum efficacy while minimizing adverse events. Companion diagnostic tests are used in a specific context that provides information that enables better decision-making about the development and use of a potential drug therapy. It is a key tool in personalized medicine and a solution to develop individualized drugs. However, in development and clinical application of such tests, there are problems in biological, technical and clinical aspects. Of primary importance is coordination among government, industry and academic professionals, to make standards and evidences for system development and application and to guide society including public and care providers, hence providing health care service with good quality.