Hamilton Study

The widely quoted "Hamilton study"¹⁷ of the prevalence of latex sensitisation amongst a group of healthcare workers has received considerable attention. All 2062 employees of a general hospital in Hamilton, Ontario, who regularly used latex gloves, were invited to participate in a survey. Attempts were made to recruit employees who were diagnosed with latex allergy before the survey. Skin prick tests were performed with latex reagents, three common inhalants, and six foods. There was a total of 1351 (66%) participants.

The prevalence of positive latex skin tests was 12.1%. This prevalence did not vary by sex, age, hospital, or smoking status, but subjects who were latex positive were significantly more likely to be atopic and significantly more likely to have positive skin tests to one or more foods. The prevalence of latex sensitivity was highest amongst laboratory workers (16.9%), and nurses and physicians (13.3%).

Glove extracts were assayed for antigenic protein, and area and personal air samples were obtained on two occasions (summer and winter) to estimate exposure to airborne latex protein. Whilst it is extremely unwise to dispute the authenticity of medical findings, it would appear that the tests performed on the gloves, like many similar studies by medical researchers, are highly questionable. The researchers claimed that the mean (SD) latex protein concentrations were 324 (227) micrograms/g in powdered surgical gloves and 198 (104) micrograms/g in powdered examination gloves.

In general, it has been assumed that powdered surgical gloves are less likely to include residual protein than powdered examination gloves, as they tend to be subject to closer control. Furthermore, those surgical gloves manufactured by the Biogel process have very low protein levels. There is no suggestion within the paper that such results might be anomalous. Similar reservations can be made about medical workers who have attempted to test glove integrity without any real effort being made to ensure that their tests or their samples are realistic. Such tests have often led to extremely high failure rates being postulated. Such work includes the notorious paper on vacuoles in latex gloves, where an artifact of the microscopy led to fears that there are pathways through latex protective gloves. This work has now been fully refuted by workers at the FDA.

References
¹⁷Liss G.M. et al, Latex allergy: epidemiological study of 1351 hospital workers. Occup. Environ. Med., 1997, 54, 335-42.