Protein Nitrogen Unit per Milliliter

**Semantic type:** Quantitative Concept

**Definition:** A measurement of the strength of an allergenic extract, one protein nitrogen unit/mL (PNU/mL) is 0.01 microgram of phosphotungstic acid-precipitable protein nitrogen dissolved in one mL of antigen extract.

**Synonyms:** - PNU per mL - PNU/Milliliter - PNU/ml - protein nitrogen units/millilitre