The assessment of irritation using clinical methods and questionnaires

Sensory irritant responses to chemical exposures are measured by a variety of methods; however, studies can be influenced from biases associated with study design and subject responses. This article reviews the different methods used to quantitate irritation. These methods primarily focus on eye and nasal mucosal irritation. Although methods to evaluate mouth, throat mucosal, and dermal irritation are also relevant, they are seldom used in actual practice. Measurements for eye irritation include tear film stability, epithelial damage, foam formation, blinking frequency, tear flow, inflammation, and hyperemia. Methods for detecting nasal mucosa irritation include measuring swelling of the nasal mucosa, peak airflows through the nose, acoustic rhinometry, and rhinostereometry, which measures thickness of the anterior nasal turbinate. Questionnaires are useful for defining a set of symptoms in an attempt to characterize dose-response relationships from controlled exposure studies or field studies, to compare rates of events in field studies, or to screen for disease. However, it is important to consider carefully the study design, goal of utilization, and constraints surrounding their application. Whichever method is used in medical surveillance or to evaluate effectiveness of industrial hygiene or engineering controls in preventing irritation effects from chemical exposure, the sensitivity, specificity, and predictive value of the irritation measurements are important factors in interpreting the results. This article reviews these various issues and offers some advice.