Platelet Activating Factor Acetylhydrolase Levels at Baseline and during Allergic Reactions

Rationale: Platelet Activating Factor Acetylhydrolase (PAF-AH) activity has been inversely correlated with allergic reaction severity. We sought to develop a rapid assay to quantify PAF-AH, to determine its utility in the diagnosis of anaphylaxis, and to examine its use as a baseline marker of potential anaphylaxis severity.

Methods: Monoclonal antibodies to PAF-AH were produced in a murine model and used to develop a Luminex assay for quantifying PAF-AH. Blood samples were obtained from healthy controls and subjects presenting to the emergency department with allergic reactions. Subjects from the emergency department were followed-up as outpatients and a baseline blood sample was obtained.

Results: The PAF-AH assay was tested in 24 healthy adults at 2 time points 1 month apart. Median PAF-AH levels were 33.20 ng/mL for healthy controls at visit 1; 33.35 ng/mL at visit 2. 59 subjects presenting with an allergic reaction have been enrolled; 18 subjects have followed-up for baseline visits. The median PAF-AH level (42.73 ng/mL) was higher at baseline in the allergic subjects (P=0.05) and significantly higher at the time of the allergic reaction (47.70 ng/mL, P<0.001) compared to the healthy controls. In subjects who returned for baseline visits, the PAH-AH levels were higher in 15 (83.3%) subjects at the time of the allergic reaction (median increase 21.8% compared to baseline).

Conclusions: PAF-AH levels were similar when measured one month apart in healthy controls. The majority of subjects had higher PAF-AH levels at the time of the allergic reaction compared to baseline, likely reflecting increased levels of Platelet Activating Factor.