Assessing dermatitis in epidemiologic studies: occupational skin disease among California grape and tomato harvesters

We conducted a cross-sectional investigation to determine whether table grape harvesters, who have significant cutaneous contact with crop-associated materials that may cause skin disease, are more likely to develop dermatitis than are a control group of tomato workers performing mechanical harvesting with minimal cutaneous contact with crop-associated substances. A secondary aim was to develop methods for studying skin disease in farm workers, including a standard questionnaire and physical examination. California table grape workers (n = 183) and tomato workers (n = 43) completed an interviewer-administered questionnaire and waist-up physical examination at their work site during harvest operations. On physical examination, pustular eruptions such as acne and folliculitis were present in 30% of subjects, and eczematous rashes were noted in 10% of subjects. Irritant or allergic contact dermatitis was diagnosed in 2% of subjects. No significant differences in prevalence for these skin conditions were observed between the two groups of workers. In contrast to the physical examination results, grape workers were more likely than tomato workers to report a rash occurring in the previous 3 months (52% vs. 19%, p less than 0.001). Explanations for this discrepancy are discussed. The sensitivity of the questionnaire for current skin conditions was 31%, and the specificity was 94%. Improved sensitivity was seen for eczematous skin conditions (55%). We conclude that questionnaires provide an efficient means of assessing subject characteristics, but may have limited sensitivity for some dermatologic outcomes.