Table 2. Key question 5a: evidence for prevention of asthma due to natural rubber latex (NRL).

First author [ref.]	Main conclusion	Origin	SIGN grade	Study type	Exposure/occupation	Subjects
LaMontagne [29]	Substitution of powdered latex gloves with low-protein powder-free NRL gloves or latex-free gloves greatly reduces NRL aeroallergens, NRL sensitisation, and NRL asthma in healthcare workers	Literature search	1+	Systematic review	NRL exposure	Eight studies ranging from exposure studies and observational data from cohort studies
Allmers [30]	Decreased use of powdered gloves and increased use of powder-free gloves correlated with decline in suspected NRL occupational asthma and skin allergy cases, 1997–2001 Conclusion: primary prevention of occupational NRL allergies is possible with properly implemented practical interventions	LaMontagne [29]	3	Case series, reported number of suspected NRL allergy cases from German healthcare system	NRL exposure from gloves	3 million insured healthcare workers in Germany
Heilman [31]	Latex aeroallergen levels and extractable latex glove allergen contents in an operating room measured on 52 consecutive days, including 19 non-surgery days, with 12 exposure crossovers On 33 surgery days, all personnel wore either high-allergen gloves (n=18 days) or low-allergen gloves (n=15 days) Internal comparison (cross-over) Conclusion: substitution of low-allergen NRL gloves for high-allergen NRL gloves can reduce latex aeroallergen levels by more than 10-fold in an operating room environment	LaMontagne [29]	2++ (cross-over design like RCT)	Prospective evaluation of an intervention	Operating room personnel exposed to NRL	Measurements on 52 days
Jones [32]	Studied dental students from first to final year in training Students used only powder-free NRL gloves and were tested annually Students were 65% atopic, but none developed latex sensitivity in 5 yrs of study Conclusion: exposure to powder-free NRL gloves was not associated with sensitisation over 5 yrs in a highly atopic population	LaMontagne [29]	2+	Prospective evaluation of intervention	NRL exposure in dental students	63 dental students at baseline, 34 at final year (loss to follow-up)
Lee [33]	Education to reduce NRL glove use in food handlers, use was reduced from 10 stalls to one Conclusion: educate food handlers to prevent NRL allergy in workers and customers	LaMontagne [29]	3	Intervention among food handlers in Australia	NRL glove use in food handlers	30 food stalls at market
Levy [34]	Final year dental students in Paris, France and London, UK completed a questionnaire and SPT with NRL extract Latex sensitivity was OR 11.3 (95% CI 2.4–53.0) for using protein-rich gloves Conclusion: use of powder-free protein poor NRL gloves may reduce latex sensitisation	LaMontagne [29]	2-	Cross-sectional study: some students used protein-rich gloves and others did not	Use of protein-rich versus protein- poor NRL gloves in dental clinic	189 fifth year (graduating) dental students working in clinics
Liss [35]	In 1996, the Ontario government recommended change to powder-free, low-protein or non-NRL gloves in healthcare, and hospitals changed related policies at the same time Researchers documented a decline in worker compensation claims for NRL occupational asthma, from 7–11 per yr in 1991–1994 to 1–2 per yr in 1997–1999 Conclusion: use of low-protein or non-NRL gloves is associated with a decrease in number of NRL occupational asthma cases	LaMontagne [29]	3	Case series based on workers' compensation claims in Ontario province, Canada	Use of powdered NRL gloves and change to low-powder NRL and non-NRL gloves in healthcare facilities	66 workers' compensation claims for NRL through 1999
Saary [36] and Tarlo [37]	Dental school in Ontario province, Canada, changed from high-protein/powdered to low-protein/non-powdered NRL gloves A positive NRL SPT in students decreased from 10% in 1995 to 3% in 2000 (p=0.03) There was a decline in per cent with urticaria, immediate pruritis and rhino-conjunctivitis, but not asthma or eczema Conclusion: suggestive preventive effect by change to low-protein/powder-free NRL gloves in dental school	LaMontagne [29]	2-	Intervention for students and staff in dental school, between cross-sectional surveys in 1995 and 2000 (two different study cohorts)	NRL gloves in dental school	131 in 1995 and 97 in 2000
Liss [35] and Tarlo [38]	Study conducted in teaching hospital in Ontario, Canada Intervention was education and medical surveillance, and change to powder-free NRL gloves Decline in symptom onsets and clinic visits after change in non-sterile gloves in 1995 and sterile gloves in 1997, to final year of study in 1999 Conclusion: NRL allergy reduced	LaMontagne [29]	3	Intervention and retrospective record review to detect NRL allergy cases in occupational health and allergy clinics	NRL in gloves in hospital	8000 employees, 52 staff with positive skin test responses and clinical NRL allergy

SIGN: Scottish Intercollegiate Guidelines Network; RCT: randomised controlled trial; SPT: skin-prick test.