The following words and terms, when used in this subchapter, have the following meanings, unless the context clearly indicates otherwise.(1) Commissioner--The commissioner of the Texas Department of State Health Services.(2) Department--The Texas Department of State Health Services.(3) Investigational drug, biological product, or device--These words are defined in Texas Health and Safety Code §490.001.(4) Severe chronic disease--A condition, injury, or illness that:(A) may be treated;(B) may not be cured or eliminated; and(C) entails significant functional impairment or severe pain.