Challenge testing in the diagnosis of occupational allergic conjunctivitis

Providing evidence for the allergic aetiology of ocular symptoms developing as a result of occupational exposure is important for compensation procedures in many countries.

To perform cellular analysis of tear fluid before and after a specific challenge test with high-molecular weight allergens in symptomatic subjects.

The subjects were 23 bakers with a history of conjunctivitis or rhinoconjunctivitis associated with occupational exposure to wheat flour and positive skin prick test with this allergen. A specific inhalation challenge test with wheat flour and a placebo test were performed. The symptom score (SS) and cellular changes in tear fluid and nasal washings were assessed.

Specific provocation test induced significant eosinophil influx in tear fluid in only six patients. No changes in the proportion of other cells could be observed. Cytological changes in tear fluid did not correlate with either ocular SS (Pearson r = 0.18, P = 0.40) or changes in the nasal lavage fluid or SS (Pearson r = 0.13, P = 0.56). However, an analysis of SS results obtained at 30 min and at 24 h after the challenge revealed that cellular changes in tear fluid correlated significantly both with the early and late changes in SS (Pearson r = 0.52, P < 0.05 and Pearson r = 0.81, P < 0.001, respectively).

Analysis of cellular changes in tear fluid during specific inhalation challenge test seems to be a valuable diagnostic tool in occupational ocular allergy. However, the discrepancy between the findings of cellular analysis and SS revealed by the present study requires further research.