Role of skin prick test and serological measurement of specific IgE in thediagnosis of occupational asthma resulting from exposure to vinyl sulphonereactive dyes

Objectives-Some patients with occupational asthma resulting from exposure t o reactive dyes have skin reactivity to the causative dyes and specific IgE to reactive dyes have been found in these patients. However, the usefulnes s of skin prick tests (SPTs) and serological measurement of specific IgE in screening, diagnosis, and monitoring the occupational asthma resulting fro m exposure to reactive dyes have not yet been assessed. In this study, the clinical validation of SPTs and measurement of specific IgE to vinyl sulpho ne reactive dyes by enzyme linked immunosorbent assay (ELISA) was evaluated . Methods-42 Patients with occupational asthma from reactive dyes (true posit ive group) were enrolled. In these the causative reactive dye was confirmed by bronchial challenge test. 93 Asymptomatic factory workers with negative challenge to the reactive dye (true negative group) and 16 unexposed contr ols with negative challenge to the reactive dye were also enrolled. Skin pr ick tests were done with 10 mg/ml reactive dye in 0.4% phenol/0.9% saline. IgE specific to reactive dye conjugated to human serum albumin (HSA) was me asured with enzyme linked immunosorbent assays (ELISAs). Results-None of the unexposed controls had a positive response to SPTs. The sensitivity (76.2% v 53.7%), specificity (91.4% v 86.0%), positive predict ive value (80.0% v 62.9%), and negative predictive value (89.5% v 80.8%) of SPTs were higher than those of ELISAs. The mean weal size of reaction to r eactive dye was weakly correlated with the ELISA optical density of IgE to reactive dye conjugate in patients with occupational asthma from reactive d yes (n=41, r=0.337, p<0.05). In four patients with occupational asthma from reactive dyes and eight control subjects exposed to reactive dye, IgE spec ific to reactive dye conjugated to HSA was detected with ELISA even though they showed negative skin reactivity. Six patients completely avoided the r eactive dye for a mean (SD) 27.8 (10.3) months, IgE specific to reactive dy es decreased in all six patients (p<0.05) during this time. Conclusions-Both SPTs and detection of IgE specific to reactive dye in seru m samples could be valuable for screening, diagnosis, and monitoring occupa tional asthma resulting from exposure to reactive dyes. These two tests wou ld complement each other.