INCIDENCE OF LATEX SENSITIZATION

To the Editor:

The article by Gautrin and colleagues (1) regarding IgE-mediated sensitization contains important observations on the incidence rate of latex sensitization in dental hygiene apprentices. The authors estimate the work-related incidence rate of latex sensitization at 2.5% per person-year among dental hygiene apprentices, 1.6% per person-year among pastry making apprentices and 0.4% among animal health apprentices. These observations are important because the only other published study of the incidence rate of latex sensitization among health care workers estimates the incidence rate at 1% per person-year (2). In contrast, there are dozens of studies of the prevalence of latex sensitization in health care workers, most of which have no referent group, provide no estimate of the relative risk of sensitization in health care workers compared with other occupations, and report prevalences between 11% (3) and 38% (4).

Although Gautrin and colleagues did not report the calculations, their results indicate that the rate of latex sensitization is not significantly higher in dental hygiene apprentices than it is among pastry-making apprentices: (incidence rate ratio: 1.6, 95% CI: 0.6 to 3.3). The rate of latex sensitization is significantly higher in dental hygiene apprentices than it is among animal health apprentices: (incidence rate ratio: 6.7, 95% CI: 2.7 to 13.8). The rate in pastry maker apprentices is also higher than it is among animal health apprentices, although not significantly (incidence rate ratio: 4.2, 95% CI: 0.8 to 12.3). This pattern of relative risks raises the possibility that pastry-making apprentices may have exposure to antigens that cross-react with latex, such as grasses (5) and wheat-derived allergens (6). The findings also raise questions about the role of latex gloves in causing latex sensitization. The authors indicate that the animal health apprentices used latex gloves when handling animals. It would be useful to know the extent to which the pastry makers and the animal health apprentices use latex rubber gloves in their work, and whether this factor explains the differences in risk. Nonetheless, these data are important because they are derived from prospective study of inception cohorts in these occupational groups. There are few opportunities to perform such studies.

The authors are to be commended for reporting the baseline prevalence, incidence rates, and determinants of latex sensitization among dental hygienists in comparison with other occupations. Continued follow up of this cohort should provide valuable information on the risks of latex sensitization.

The University of Michigan School of Public Health, Ann Arbor, Michigan

1. Gautrin D, Ghezzo H, Infante-Rivard C, Malo JL. Incidence and determinants of IgE-mediated sensitization in apprentices. Am J Respir Crit Care Med 2000; 162: 1222-1228 [Abstract/Free Full Text].

2. Sussman GL. Incidence of latex sensitization among latex glove users. J Allergy Clin Immunol 1998; 101: 171-178 [Medline].

3. Lagier F, Verloet D, Lhermet I, Poyen D. Prevalence of latex allergy in operating room nurses. J Allergy Clin Immunol 1992; 90: 319-322 [Medline].

4. Kibby T, Akl M. Prevalence of latex sensitization in a hospital employee population. Ann Allergy Asthma Immunol 1997; 78: 41-44 [Medline].

5. Merrett TG, Merrett J, Kekwick R. The prevalence of immunoglobulin E antibodies to the proteins of rubber (Hevea brasiliensis) latex and grass (Phleum pratense) pollen in sera of British blood donors. Clin Exper Allergy 1999; 29: 1572-1578 .

6. Baldo BA, Sutton R, Wrigley CW. Grass allergens, with special reference to cereals. Progress in Allergy 1982; 30: 1 .

From the authors:

We thank Drs. Garabrant and Franzblau for their comments on our study (1).

Drs. Garabrant and Franzblau calculated the incidence rate ratios based on the incidence of latex sensitization per person-years, and we agree with their results. We chose to calculate the rate ratios using the cumulated incidence for the whole duration of the training by persons at risk on entry to illustrate the risk of sensitization associated with the apprenticeship in the three programs. Our results indicated that the cumulative incidence rate of latex sensitization was significantly greater in dental hygiene apprentices (7/110) compared with both pastry makers (3/185) (IRR = 3.92, CI = 1.04- 14.86) and animal health technicians (4/391) (IRR = 6.22, CI = 1.85-20.86). The rate of latex sensitization in pastry makers was greater than in animal health technicians, but not significantly (IRR = 1.59, CI = 0.36-7.01).

The comment by Drs. Garabrant and Franzblau on the possibility that apprentice pastry makers may have exposures to antigens that cross-react with latex, thus explaining our finding on the incidence of latex sensitization in three apprentice pastry-makers, is very interesting. This comment led us to examine further our data; we found that among these three subjects, two developed sensitization to mixed flour-derived antigens. In addition, the only dental hygiene technology student who developed skin reactivity to mixed flour-derived antigens also developed latex sensitization. Among the four animal health apprentices with incident latex sensitization, one was sensitized to grass-derived allergens at baseline and one became sensitized during the study. Our results therefore seem to be in agreement with the suggestions by Drs. Garabrant and Franzblau.

Complementing the conclusions of our paper is the fact that the apprentice pastry makers occasionally use latex or vinyl gloves if they have a hand wound or when making chocolates, which represents a negligible time period (on average, 1 h/wk). The animal health apprentices use latex gloves when doing surgical procedures and vinyl or latex gloves when handling animals. On the other hand, the dental hygiene apprentices use only latex gloves; we estimated that they use these an average of 10 h/wk during the second year of training and 30 h/wk during the third (2).

We therefore feel confident that the excess in the incidence of latex sensitization in dental hygiene apprentices is due to exposure to latex gloves for longer periods of time.

Hôpital du Sacré-Coeur, Montreal, Canada

Claire Infante-Rivard

McGill University, Montreal, Canada

1. Gautrin D, Ghezzo H, Infante-Rivard C, Malo JL. Incidence and determinants of IgE-mediated sensitization in apprentices: a prospective study. Am J Respir Crit Care Med 2000; 162: 1222-1228 .

2. Archambault S, Malo JL, Infante-Rivard C, Ghezzo H, Gautrin D. Incidence of sensitization, symptoms, and probable occupational rhinoconjunctivitis and asthma in apprentices starting exposure to latex. J Allergy Clin Immunol (In press)