Protein nitrogen unit

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The protein nitrogen unit (PNU) measures the potency of the compounds used in allergy skin tests, and is equivalent to 0.01 microgram (µg) of phosphotungstic acid-precipitable protein nitrogen.[1] Potency measurements depend on the measurement technique, so that results from different manufacturers cannot be reliably compared. as a result, PNUs are being replaced by bioequivalent allergy units (BAU), which are measured by skin testing using reference preparations of standard potency.[2]


  1. ^ May, JC; Sih, JT; Best, J; Douglas, G; Rancour, JM; Renker, HR; Spingola, F; Van Daele, L; Zudeck, S; et al. (November 1981). "Protein nitrogen unit precipitation procedure for allergenic extracts: collaborative study". J Assoc off Anal Chem. 64 (6): 1435–8. PMID 7309663.  Site is an abstract provided by PubMed
  2. ^ Ross, Rowlett (2002). "P". How Many? A Dictionary of Units of Measurement. University of North Carolina at Chapel Hill. Retrieved 2009-02-05. 

The end product of protein nitrogen in man is Urea