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Clin Exp Allergy. 2009 Sep;39(9):1390-6. doi: 10.1111/j.1365-2222.2009.03276.x. Epub 2009 May 26.

Clinical predictors for biphasic reactions in children presenting with anaphylaxis.

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  • 1Department of Allergy and Immunology, Royal Children's Hospital, Melbourne, Australia.



One of the main reasons for hospital admission once a child has been stabilized following anaphylaxis is to monitor for a biphasic reaction. However, only a small percentage of anaphylactic episodes involve biphasic reactions that would benefit from admission. Identification of predictive factors for a biphasic reaction would assist in determining who may benefit from prolonged observation.


To determine predictive factors for biphasic reactions in children presenting with anaphylaxis.


This was a retrospective study of children presenting with anaphylaxis to a major paediatric emergency department over a 5-year period.


There were 95 uniphasic (87%), 12 (11%) biphasic and two protracted reactions (2%). One child with a protracted reaction died. For the management of the primary anaphylactic reaction, children developing biphasic reactions were more likely to have received >1 dose of adrenaline (58% vs. 22%, P=0.01) and/or a fluid bolus (42% vs. 8%, P=0.01) than those experiencing uniphasic reactions. The absence of either factor was strongly predictive of the absence of a biphasic reaction (negative predictive value 99%), but the presence of either factor was poorly predictive of a biphasic reaction (positive predictive value of 32%). All biphasic reactors, in which the second phase was anaphylactic, received either >1 dose of adrenaline and/or a fluid bolus.


Children who received >1 dose of adrenaline and/or a fluid bolus for treatment of their primary anaphylactic reaction were at increased risk of developing a biphasic reaction.

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