[Specific serum IgG antibodies against phthalic anhydride in occupationally exposed workers]

Specific IgG antibodies against phthalic anhydride (PA) was determined in fifty heavily exposed workers, thirty non-exposed subjects and twelve patients with asthma as control groups. ELISA method was used by phthalic anhydride conjugated to human serum albumin antigen. The data demonstrated that specific IgG level was significantly increased only in heavily exposed workers. The average OD value was 0.6 +/- 0.47 (positive rate 78%), but 0.04 +/- 0.03 and 0.05 +/- 0.03 respectively in the two control groups. There was no association between the antibody level and clinical symptoms or the duration of exposure. The meaning of such increase requires further study. We believe, however, that in vitro specific IgG assay can be used as an indication of exposure to PA, or for etiological diagnosis of asthmatic patient and as a means to differential diagnosis.