Protein nitrogen unit

{{short description|Measurement unit}}

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.

{{Cite journal | last1 = May | first1 = JC | last2 = Sih | first2 = JT

| title = Protein nitrogen unit precipitation procedure for allergenic extracts: collaborative study

| journal = Journal of the Association of Official Analytical Chemists | volume = 64 | issue = 6 | pages = 1435–8

| date = November 1981 | pmid = 7309663 | last3 = Best | first3 = J | last4 = Douglas | first4 = G | last5 = Rancour | first5 = JM | last6 = Renker | first6 = HR | last7 = Spingola | first7 = F | last8 = Van Daele | first8 = L | last9 = Zudeck | first9 = S |display-authors=etal |doi=10.1093/jaoac/64.6.1435| doi-access = free }} 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.

{{cite web | last = Ross | first = Rowlett | title = P

| work = How Many? A Dictionary of Units of Measurement

| publisher = University of North Carolina at Chapel Hill

| year = 2002 | url = http://www.unc.edu/~rowlett/units/dictP.html

| accessdate = 2009-02-05}}