Exhaled and Nasal Nitric Oxide is Increased in Laboratory Animal Allergy

Background: Allergens from rats, mice, guinea pigs or rabbits cause up to 30% of exposed persons to develop specific immunoglobulin E (IgE) responses. Laboratory animal allergy (LAA) is among the highest occupational risks for asthma in the UK. Elevated levels of nitric oxide (NO) are found in exhaled breath in asthma. In LAA symptoms may progress from conjunctivitis, rhinitis to asthma. Health surveillance aims to detect early sensitization.

Objective: To assess whether an association exists between LAA and exhaled NO.

Methods: A cross-sectional study was performed in 39 laboratory workers undergoing LAA health surveillance. Volunteers completed two health questionnaires, had skin-prick tests, spirometry, total IgE and RAST tests. Exhaled and nasal NO was measured by chemiluminescence analyser (LR2000, Logan Research, Rochester, UK).

Results: There were 23 asymptomatic subjects (mean age 29.53 years) and 16 symptomatic subjects (29.63 years, P=0.95); 9 early LAA, seven LAA asthma. Exhaled NO was raised in those with LAA symptoms 17.97 ppb+/-1.24 (mean+/-SEM) compared with asymptomatics 6.08 ppb+/-1.15, P < 0.05. A trend of increased NO by allergic status was observed; asymptomatic, to early LAA, to asthma. One-way analysis of variance compared differences between groups (F ratio 13.93, P < 0.001). Symptomatic subjects also had raised nasal NO, vs asymptomatic subjects (mean difference 378 ppb, P < 0.05). A trend was again observed by allergic status (F ratio 5.28, P=0.01).

Conclusion: Raised NO levels in LAA increasing with symptom severity suggest NO may prove a useful additional tool in monitoring for LAA, and possibly the response to exposure reduction or allergy due to other respiratory sensitizers.