Fel d 1 specific IgE measurement for dog exclusive owners co-sensitized to dog and cat.

BACKGROUND: The diagnosis of the culprit allergen depends on exposure, symptoms at exposure, and the presence of specific IgE (sIgE). Pet allergens are sticky and can sensitize individuals without adoption history. Exclusive dog owners frequently exhibit both dog (e5) and cat dander sIgE (e1). We assessed whether the measurement of Fel d 1 sIgE (e94) can discriminate true cat sensitization from false positivity by cross-reactivity in the exclusive dog owners. METHODS: Thirty-one patients with respiratory allergies who exclusively owned dogs were enrolled for this study. e5, e1, and e94 were measured with ImmunoCAP. ELISA inhibition was performed to assess cross-reactivity. RESULTS: About 81% of patients (25/31) were both e5 and e1 positive, and 8 were also positive for e94. In the e94 positive, cat dander exhibited higher maximum inhibition of cat sIgE (94% vs 88%) and demonstrated lower IC(50) (6.5 vs 737.9 BAU/mL) compared to dog dander. Conversely, in the e94 negative, dog dander demonstrated higher maximum inhibition of cat dander sIgE (71.9% vs 56.2%) and lower IC(50) (172 vs 1947 BAU/mL) compared to cat dander. In the e94 positive, dog dander exhibited higher maximal inhibition for dog sIgE (91.5 vs 76.1%) and lower IC(50) (10.6 vs 1679 BAU/mL) compared to cat dander, whereas in the e94 negative, the IC(50) for cat dander could not be determined. CONCLUSIONS: Genuine co-sensitization to cats is notable even in individuals who exclusively own dogs. Positive e94 results could discriminate authentic cat sensitization from false positivity by cross-reactivity in these patients, underscoring the importance of comprehensive allergy assessment.