Urinary eosinophil protein X in children with atopic dermatitis: relation to atopy and disease activity.

Background: Parameters of eosinophil inflammation have been suggested as markers of disease activity in atopic dermatitis (AD), but the value of urinary eosinophil protein X (U-EPX) in children with AD, as well as the influence of allergic sensitization, is not known.
Methods: We measured U-EPX in 59 atopic and 29 nonatopic children with mild (n = 32), moderate (n = 34), and severe (n = 22) AD, as well as in 64 controls.
Results: U-EPX was increased in children with AD (110; 67-164 microg/mmol creatinine, median; quartiles) compared to controls (62; 41-95, P<0.001). Children with mild (97; 63-164, P < 0.01), moderate (108; 67-157, P < 0.01), and severe disease (152; 99-202, P < 0.001) had levels of U-EPX higher than controls. U-EPX was significantly higher in children with severe AD than in mild and moderate disease (P < 0.05 for both). Children with AD and a positive skin prick test (120; 81-176) had higher levels of U-EPX than children with a negative skin prick test (87; 56-155, P<0.05).
Conclusions: U-EPX is significantly increased in children with AD and may reflect disease activity. U-EPX may also reflect differences in eosinophil activation between those sensitized and those not sensitized to common allergens.