Introduction: The prevalence of positive skin tests to Anisakis simplex is high compared with the low incidence of true gastroallergic Anisakiasis. There is little information about the prevalence of positive conjunctival tests in A. simplex-sensitized individuals. This study assesses the predictive value of conjunctival provocation test in two groups of A. simplex-sensitized subjects and negative controls.
Methods: Group A consisted of 28 individuals with a clinical history strongly suggestive of gastroallergic anisakiasis and group B, of 32 individuals without such history. The 60 individuals had positive skin tests and in vitro specific IgE determinations to A. simplex. Skin and conjunctival provocation tests were performed with an extract of A. simplex at a concentration of 1 mg of lyophilized material per ml.
Results: Conjunctival provocation tests were positive in 21/28 (75%) of group A patients and in 10/32 (31%) of group B patients. This difference was statistically significant (p < 0.015); the odds ratio was 6.6 (2.11-20.5; p < 0.05). The diagnostic value of the conjunctival provocation test was expressed by the following statistical indicators: sensitivity 75% (55.8%-88.6%), false positive 25% (11.4%-45.2%), specificity 68.7% (49.9%-83.2%), false negative 31.2% (16.7%-50%), positive predictive value 67.7% (48.5%-82.7%), negative predictive value 75.9% (56.1%-89%), Yuden index 1.43. There were no statistical differences related to age, sex, or atopic status in patients with a positive or negative conjunctival challenge. Total and specific IgE levels to A. simplex were significantly greater (p < 0.05 and p < 0.001, respectively) in the group of patients with a positive challenge.
Conclusions: The results demonstrate that positive conjunctival provocation tests and high specific and total IgE levels are more prevalent in patients with a clinical history strongly suggestive of gastroallergic anisakiasis. Despite the significant differences obtained in both groups, this test has a limited diagnostic value to clinically discriminate patients with a history consistent with gastroallergic anisakiasis.