50 Percent Tissue Culture Infective Dose

**Semantic type:** Quantitative Concept

**Definition:** A potency unit defined as a minimal dose of infectious material at which preparation causes cytopathic effects (changes in the morphology and metabolism of tissue culture cells, indicating cell death, due to suspected infection) in the 50% of the tissue culture-containing flasks inoculated with that dilution of infectious material in the product potency assay or pathogen activity assay.

**Synonyms:** - 50% Tissue Culture Infective Dose - TCID50