TABLE I.

Allergen concentration of reference standards measured by ELISA using the UAS

	Units	Allergen	Concentration
WHO-IUIS standards*
Dermatophagoides pteronyssinus 82/518	100,000 IU/ampoule	Der p 1	7.2 µg/ampoule
Dog hair 84/685	100,000 IU/ampoule	Can f 1	20.4 µg/ampoule†
FDA standards‡
D pteronyssinus E8	10,000 AU/mL	Der p 1	20.3 µg/mL
D pteronyssinus E10	10,000 AU/mL	Der p 1	27.6 µg/mL
D pteronyssinus E8	10,000 AU/mL	Der p 2	23.4 µg/mL
D pteronyssinus E10	10,000 AU per mL	Der p 2	23.5 µg/mL
D farinae E9	10,000 AU/mL	Der f 1	19.9 µg/mL
D farinae E10	10,000 AU/mL	Der f 1	29.2 µg/mL
D farinae E9	10,000 AU/mL	Der f 2§	19.2 µg/mL
D farinae E10	10,000 AU/mL	Der f 2§	15.0 µg/mL
Cat hair E4	10,000 BAU/mL or 7.0 Fel d 1 units/mL	Fel d 1	5.4 µg/mL‖
Cat pelt E4	10,000 BAU/mL or 14.8 Fel d 1 units/mL	Fel d 1	15.6 µg/mL‖
Cat hair E5	10,000 BAU/mL or 22.0 Fel d 1 units per mL	Fel d 1	24.8 µg/mL‖

BAU, Bioequivalent allergy unit.

^*Mean of duplicate determinations.

^†Based on these data, 1 IU Can f 1 = ~5 ng Can f 1.

^‡Mean data from measurements by 2 operators on 3 separate occasions. The values for Fel d 1 units in the cat hair and pelt standards were determined by radial immunodiffusion by the FDA (data kindly provided by Cherry Valerio, FDA Center for Biologics Evaluation and Research).

^§Determined using a separate in-house natural Der f 2 standard with a concentration of 1.25 mg/mL by amino acid analysis.

^‖1 FDA unit Fel d 1 = ~1 µg Fel d 1.