Conjunctival Provocation Test With Blomia tropicalis

Abstract

Background: Conjunctival provocation test (CPT) is used to demonstrate clinical relevance to a specific allergen. Blomia tropicalis (Bt) is a prevalent allergen in tropical regions. Its major allergen Blo t 5 is commonly detected in house dust in Brazil. Patients with allergic rhinoconjunctivitis (ARC) have IgE antibodies to Bt although it may not indicate clinical allergy.Objective: The purpose of this study is to demonstrate the role of CPT in clinical allergy to Bt in allergic conjunctivitis (AC).Methods: CPT was performed in asymptomatic subjects with ARC (n = 26) outside the grass pollen season. They had positive skin prick tests (SPT) to Bt and other common inhalant allergens and they were off topical or systemic antihistamines. Standardized allergens were used for CPT (Blo t 5 462.5 ng/mL in 1:1 solution, Alk Abelló). CPT was conducted on a control group of subjects (n = 29) without symptoms of ARC and with negative SPT. CPT was performed with progressive doses of allergen solutions in normal saline (1:32, 1:16, 1:8, 1:4, 1:2). CPT with the same allergen dose that elicited a positive reaction was repeated one week later. The protocol was approved by the local Ethics Board and signed informed consent was obtained from all participants.Results: There were 92% (24/26) of positive CPT in subjects sensitized to Bt. Significant association was found between SPT and CPT results with Bt (p < 0.0001). CPT had 92% sensitivity and 100% specificity when compared to SPT results. Positive reactions with the same dose or one immediately higher occurred in 21 out of 22 subjects who repeated TPC 1 week later. Mild transient nasal symptoms (21/24) were the major side effects of positive CPT followed by moderate periorbital edema which occurred in 41% (10/24). One controlled asthmatic BT-sensitized subject developed wheezing and dyspnea during a positive CPT with Bt that cleared with inhaled albuterol (400 mcg). There were no reactions whatsoever of CPT in non-allergic subjects.Conclusion: This study demonstrated that Bt may cause allergic conjunctivitis in our population. In addition, CPT is a safe and reproducible test if standardized allergens are used.

Frequent IgE recognition of Blomia tropicalis allergen molecules in asthmatic children and young adults in equatorial Africa

“…This might be due to cross-reactivity between Der p 2 and Blo t 2, or because we used an isoform (Blo t 2.0104) that is not prevalent in the mite and might show lower IgE-reactivity ( 43 ). It must be noted that little is known about the distribution of mite species in sub-Saharan Africa, but there is evidence that B. tropicalis represents an important mite species also in other regions with a hot and humid climate ( 44 , 45 ). Unfortunately, B. tropicalis extracts were not used for skin prick testing, since it was not expected by the clinical investigators that Blomia might be a genuinely sensitizing allergen source in Gabon.…”

EAACIMolecular Allergology User's Guide 2.0

“…Although not widely accepted as a diagnostic procedure, a nasal provocation test with mite extracts is another important tool for defining the clinical relevance of sensitization and detecting cases of local rhinitis associated to negative skin tests. Also, conjunctival and nasal provocation tests with B. tropicalis have been suggested as a diagnostic procedure in the clinic 735 . Measurement of mite allergens in dust from the house can be very helpful.…”

Organ‐specific allergen challenges in airway allergy: Current utilities and future directions

“…This clarification would be particularly useful in patients on standard pharmacotherapy who continue having bronchial, nasal, or conjunctival symptoms, as it can guide a different therapeutic approach (e.g., AIT and allergen avoidance measures) to achieve and maintain control 47 . Similarly, these tests may help decide the composition of AIT, especially in polysensitized patients with perennial symptoms 48 . Moreover, the CAC has been proposed to monitor the effect of AIT (e.g., to decide whether the treatment should be stopped after 3 years or continued up to 5 years), 49 although the NAC might represent an alternative in this regard.…”

“…47 Similarly, these tests may help decide the composition of AIT, especially in polysensitized patients with perennial symptoms. 48 Moreover, the CAC has been proposed to monitor the effect of AIT (e.g., to decide whether the treatment should be stopped after 3 years or continued up to 5 years), 49 although the NAC might represent an alternative in this regard. Moreover, the CAC can help differentiate between allergen-driven and intrinsic symptoms in patients with atopic keratoconjunctivitis.…”