Protein nitrogen 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. 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.

The end product of protein nitrogen in man is Urea

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