11-24-2021, 06:28 AM
Latex Medical Gloves: Time for a Reappraisal
Many hospitals have implemented policies to restrict or ban the use of devices made of natural rubber latex (NRL) in healthcare as precautionary measures against the perceived risk of NRL allergy. Changes in glove technology, progress in measuring the specific allergenic potential of gloves and a dramatic decrease in the prevalence of NRL allergies after interventions and education prompted us to revisit the basis for justifiable glove selection policies. The published Anglophone literature from 1990 to 2010 was reviewed for original articles and reviews dealing with the barrier and performance properties of NRL and synthetic gloves and the role of glove powder. The review shows that NRL medical gloves, when compared with synthetic gloves, tend to be stronger, more flexible and better accepted by clinicians. The introduction of powder-free gloves has been associated with reductions in protein content and associated allergies. Recently, new methods to quantify clinically relevant NRL allergens have enabled the identification of gloves with low allergenic potential. The use of low-protein, low-allergenic, powder-free gloves is associated with a significant decrease in the prevalence of type I allergic reactions to NRL among healthcare workers. Given the excellent barrier properties and operating characteristics, dramatically reduced incidences of allergic reactions, availability of specific tests for selection of low-allergen gloves, competitive costs and low environmental impact, the use of NRL gloves within the hospital environment warrants reappraisal.
In recent years, many hospitals and health care settings around the world have decided to restrict the use or totally ban all natural rubber latex (NRL) devices as precautionary measures to NRL allergy threats. As is widely acknowledged, type I or IgE-mediated NRL allergy has, for several years, been one of the most significant occupational health problems [for reviews, see [1,2,3]]. However, it is now also acknowledged that new cases of NRL allergy have reduced significantly and sometimes virtually disappeared in countries and hospital regions where health authorities have required the use of low-allergen/low-protein, non-powdered protective medical gloves. Thus, policies which ban the use of NRL devices may be an overreaction that can lead to unexpected compromises in the primary purpose of using protective gloves, that is, providing a competent barrier to protect against infections for both healthcare professionals and the patients [4,5]. These controversies prompted us to revisit the basis for justifiable glove selection policies.
As is well known, NRL has been used as a material for the production of gloves for almost a century. Throughout the 1990s there were increasing concerns about transmittable diseases, particularly HIV infection and hepatitis, which resulted in a dramatic increase in the use of NRL gloves. Escalating glove use in the 1990s was associated with the rise in reports of allergic reactions to NRL gloves among healthcare workers [1,6,7,8,9,10]. The increased demand for gloves led to an upsurge in glove production, especially in Malaysia. Between 1987 and 1989 the Malaysian Rubber Development Board received over 400 applications to form glove companies where previously only 25 existed [11]. Early on in the history of NRL allergy, some authors [12,13] suggested that the increased production in response to the sudden upsurge for latex gloves often led to inadequate leaching to reduce protein levels.
The healthcare community requires medical gloves, both for examination and surgery, in order to provide a barrier that prevents transmission of micro-organisms to and from patients [4]. Many factors are involved in the choice of materials for the production of medical gloves, which relate to both the protective effect as well as ease and comfort of use [14,15]. For a large number of healthcare practitioners, NRL continues to be the glove material of choice [15,16].
The negative aspect of NRL glove use, linked to the allergy problems, has gained substantial media coverage, in addition to the publication of a significant number of scientific papers. In reaction to the media and scientific coverage, and to rising compensation claims, many hospitals around the world have implemented new latex allergy and glove policies, resulting in the substitution of NRL gloves with synthetic gloves in certain areas, on specific patients or by sensitized staff. More recently, a number of high profile hospitals, exemplified by Johns Hopkins Hospital in Baltimore, Md., USA, and the Cleveland Clinic’s network of nine hospitals in Cleveland, Ohio, USA, have gone ‘latex free’ [5]. As a result, a small but increasing number of medical practitioners only have access to gloves made from synthetic materials. Such policies require full consideration of all of the factors involved, including also glove functionality as well as costs incurred, both directly and indirectly on the environment.
Following recognition of the problem of NRL sensitivity in the late 1980s and early 1990s, many changes were made in the production processes for NRL gloves and in the implementation of latex-sensitivity protocols in hospitals. In recent years, these changes have resulted in a significant reduction in the prevalence rates of allergic reactions to NRL. Experience from the Mayo Clinic, Rochester, Minn., USA [17] and Finland [18] showed that the change by an institute or hospital district specifically to low-allergen gloves or to gloves with undetectable allergen contents, led to a decrease in the incidence of new cases of occupational allergy. In Germany, Allmers et al. [19] showed that a combination of educating physicians and administrators, together with regulations requiring that healthcare facilities only purchase low-protein, powder-free NRL gloves, can even lead to prevention of sensitization.
This review compares the key properties of gloves made of NRL and synthetic source materials and examines glove barrier and functional characteristics, recent changes in glove technology, developments in NRL allergen measurement methodology as well as priority given by clinicians and other health care workers. The Anglophone literature limited largely to the period from 1990 to 2010 was surveyed for original research reports and review articles addressing also specifically the evidence for the consequent reductions in risk of allergic reactions and changes in the epidemiology of NRL allergies.
Glove Source Materials
Many plants produce liquid latex, but the natural material, NRL, used in rubber manufacture is almost exclusively obtained from the Hevea brasiliensis tree. It contains the rubber polymer, cis-poly-isoprene, as well as varying amounts of a large number of different proteins [20,21,22]. Various chemicals, such as accelerators, activators, anti-oxidants and vulcanizing agents, are used in the manufacture of medical gloves [[23]; for review, see [24]] but a large proportion of these chemicals are then leached out in the further stages of production, through processes such as ‘wet-gel leaching’. These leaching processes also remove the majority of the water-soluble proteins found in NRL [24].
The raw materials for synthetic glove manufacture include vinyl (polyvinyl chloride), nitrile (acetonitrile butadiene), neoprene, polyisoprene, polychloroprene, polyurethane and polyethylene, which are generally derived from oil chemistry. Nitrile is very similar in its polymer chemical structure to NRL and, in this respect, may be considered as synthetic latex.
Deproteinised latex, being composed of enzyme-treated NRL, has also been used as the source material for nitrile gloves. We are not aware of published reports in which gloves made of deproteinised NRL have been compared with conventional NRL gloves, especially with respect to their allergenic properties, although there are reports that NRL-allergic patients can tolerate condoms made from this material [26].
Recently, liquid latex from a North American and Mexican desert shrub, Parthenium argentatum, commonly known as Guayule, has been introduced as source material for gloves [27]. The obvious advantage of Guayule is that it is not botanically related to H. brasiliensis and, for the time being, no reports about type I allergies to these gloves have been reported.
Glove Properties
Barrier Properties
The primary function of gloves is to provide a competent barrier to protect against infections for both healthcare professionals and the patients. Gloves used by healthcare workers need to be single use for each patient contact and treatment, although it is recommended that prolonged and indiscriminate use should be avoided to minimize the risk of sensitization [4]. They are required in various situations such as invasive procedures and contact with non-intact skin, mucous membranes or sterile sites. As such, leakage must be minimal, even when apparently undamaged, and various standards have been developed in order that all gloves perform adequately regardless of material [4]. They should be easy to put on, comfortable to wear and provide adequate, durable protection [15].
The durability of barrier protection has been examined in a number of studies and it has been shown that NRL gloves provide lower rates of perforation and lower viral leakage rates than vinyl gloves [24,28,29]. In a study that examined gloves after manipulation to simulate in-use conditions, the failure rate was 0–4% for NRL, 1–3% for nitrile and 12–61% for vinyl gloves, indicating better barrier protection by NRL and nitrile gloves, compared to vinyl [29]. In another study where gloves were stressed according to a designated protocol before examining for leakage properties, failure rates were 2.2% for NRL and 1.3% for nitrile gloves, which were again better than for vinyl or copolymer (8.2% for each) [30]. Barrier integrity following an abrasion test demonstrated that NRL gloves were better than vinyl, although not as good as either nitrile or neoprene [31].
A study in the USA in 2004 performed post-usage examination and testing of surgeons’ gloves after routine surgical procedures. The results revealed higher after-use defects for non-latex compared with latex disposable gloves [32]. Compared with NRL gloves, the odds ratio for defects was 1.39 (95% confidence interval 1.12–1.73) for neoprene and 1.90 (95% confidence interval 1.15–3.13) for nitrile gloves. In addition, the surgeons reported significantly greater satisfaction with regard to factors such as quality, safety and durability for latex compared with latex examination gloves. These results should probably be treated with caution because the surgeons had never used non-latex gloves before for routine surgery (acknowledged by the authors as a possible bias) and only 215 nitrile gloves were used compared to 2,647 latex and 3,624 neoprene gloves. In addition, the main difference in the study was in visible leaks, with no significant difference in water leaks, which may be explained by the low tear propagation strength of nitrile/neoprene. Similar differences between neoprene and NRL have been demonstrated in another study [33] where it was noted that punctures in neoprene gloves were detected more readily by surgeons than punctures in NRL gloves.
A recent study [34], comparing synthetic polyisoprene and NRL gloves during heavy orthopaedic surgery with high risk of perforations, revealed a significantly higher perforation rate in latex-free gloves (80.0%) compared with NRL gloves (34.4%). Again, the study was poorly controlled and open to criticism because glove usage was not randomized, being based on two surgical teams in two different hospitals, one using NRL, the other using polyisoprene. It is, however, interesting that these three studies appear to detect highly significant differences in perforation rates between NRL and non-NRL [32,33,34].
Fit and Comfort
According to the Scientific Committee on Medicinal Products and Medical Devices of the European Commission [35], nitrile gloves are usually of lower tensile strength than surgical gloves, but their elastic modulus, or stiffness, is somewhat higher. In addition, nitrile has a higher permanent set than latex, meaning that once stretched it does not fully recover. Thus, nitrile gloves tend to be designed to fit more loosely than latex, and the combination of these properties may affect the users’ tactile sensation and delicacy of touch. This has been confirmed by a study [36] where participants noted that nitrile gloves that fitted their fingers were too narrow for their hands and gloves that fitted their hands were too large for their fingers. During this research, it was confirmed that there are detectable differences between nitrile and latex, where a pegboard test demonstrated an 8.6% increase in fine finger dexterity for latex over nitrile, although no differences related to gross dexterity. Whilst it is not clear at present what the practical effects of this research mean, it does appear that the stiffness of nitrile may affect user dexterity. The study also questioned users about their preferred material, with 67% preferring latex and 21% preferring nitrile.
Thus, a variety of factors, including glove strength, abrasive resistivity, dexterity and comfort, should be taken into account when selecting gloves for specific needs.
Enhanced Barrier Performance by Means of Double Gloving
When carrying out operations, perforations in gloves often go unnoticed and there is frequently a risk of contamination and exposure to blood-borne pathogens [37,38].
As a result, double gloving has been routinely used by a proportion of surgeons since the early 1990s. However, double gloving is reported to be less common in the UK, Europe and the USA than in other countries, except in the areas of orthopaedics and maxillofacial surgery [38,39]. Double gloving is generally carried out with two layers of NRL gloves [38], although sometimes the inner glove can be synthetic, which may reduce the risk of allergic reactions.
Many hospitals have implemented policies to restrict or ban the use of devices made of natural rubber latex (NRL) in healthcare as precautionary measures against the perceived risk of NRL allergy. Changes in glove technology, progress in measuring the specific allergenic potential of gloves and a dramatic decrease in the prevalence of NRL allergies after interventions and education prompted us to revisit the basis for justifiable glove selection policies. The published Anglophone literature from 1990 to 2010 was reviewed for original articles and reviews dealing with the barrier and performance properties of NRL and synthetic gloves and the role of glove powder. The review shows that NRL medical gloves, when compared with synthetic gloves, tend to be stronger, more flexible and better accepted by clinicians. The introduction of powder-free gloves has been associated with reductions in protein content and associated allergies. Recently, new methods to quantify clinically relevant NRL allergens have enabled the identification of gloves with low allergenic potential. The use of low-protein, low-allergenic, powder-free gloves is associated with a significant decrease in the prevalence of type I allergic reactions to NRL among healthcare workers. Given the excellent barrier properties and operating characteristics, dramatically reduced incidences of allergic reactions, availability of specific tests for selection of low-allergen gloves, competitive costs and low environmental impact, the use of NRL gloves within the hospital environment warrants reappraisal.
In recent years, many hospitals and health care settings around the world have decided to restrict the use or totally ban all natural rubber latex (NRL) devices as precautionary measures to NRL allergy threats. As is widely acknowledged, type I or IgE-mediated NRL allergy has, for several years, been one of the most significant occupational health problems [for reviews, see [1,2,3]]. However, it is now also acknowledged that new cases of NRL allergy have reduced significantly and sometimes virtually disappeared in countries and hospital regions where health authorities have required the use of low-allergen/low-protein, non-powdered protective medical gloves. Thus, policies which ban the use of NRL devices may be an overreaction that can lead to unexpected compromises in the primary purpose of using protective gloves, that is, providing a competent barrier to protect against infections for both healthcare professionals and the patients [4,5]. These controversies prompted us to revisit the basis for justifiable glove selection policies.
As is well known, NRL has been used as a material for the production of gloves for almost a century. Throughout the 1990s there were increasing concerns about transmittable diseases, particularly HIV infection and hepatitis, which resulted in a dramatic increase in the use of NRL gloves. Escalating glove use in the 1990s was associated with the rise in reports of allergic reactions to NRL gloves among healthcare workers [1,6,7,8,9,10]. The increased demand for gloves led to an upsurge in glove production, especially in Malaysia. Between 1987 and 1989 the Malaysian Rubber Development Board received over 400 applications to form glove companies where previously only 25 existed [11]. Early on in the history of NRL allergy, some authors [12,13] suggested that the increased production in response to the sudden upsurge for latex gloves often led to inadequate leaching to reduce protein levels.
The healthcare community requires medical gloves, both for examination and surgery, in order to provide a barrier that prevents transmission of micro-organisms to and from patients [4]. Many factors are involved in the choice of materials for the production of medical gloves, which relate to both the protective effect as well as ease and comfort of use [14,15]. For a large number of healthcare practitioners, NRL continues to be the glove material of choice [15,16].
The negative aspect of NRL glove use, linked to the allergy problems, has gained substantial media coverage, in addition to the publication of a significant number of scientific papers. In reaction to the media and scientific coverage, and to rising compensation claims, many hospitals around the world have implemented new latex allergy and glove policies, resulting in the substitution of NRL gloves with synthetic gloves in certain areas, on specific patients or by sensitized staff. More recently, a number of high profile hospitals, exemplified by Johns Hopkins Hospital in Baltimore, Md., USA, and the Cleveland Clinic’s network of nine hospitals in Cleveland, Ohio, USA, have gone ‘latex free’ [5]. As a result, a small but increasing number of medical practitioners only have access to gloves made from synthetic materials. Such policies require full consideration of all of the factors involved, including also glove functionality as well as costs incurred, both directly and indirectly on the environment.
Following recognition of the problem of NRL sensitivity in the late 1980s and early 1990s, many changes were made in the production processes for NRL gloves and in the implementation of latex-sensitivity protocols in hospitals. In recent years, these changes have resulted in a significant reduction in the prevalence rates of allergic reactions to NRL. Experience from the Mayo Clinic, Rochester, Minn., USA [17] and Finland [18] showed that the change by an institute or hospital district specifically to low-allergen gloves or to gloves with undetectable allergen contents, led to a decrease in the incidence of new cases of occupational allergy. In Germany, Allmers et al. [19] showed that a combination of educating physicians and administrators, together with regulations requiring that healthcare facilities only purchase low-protein, powder-free NRL gloves, can even lead to prevention of sensitization.
This review compares the key properties of gloves made of NRL and synthetic source materials and examines glove barrier and functional characteristics, recent changes in glove technology, developments in NRL allergen measurement methodology as well as priority given by clinicians and other health care workers. The Anglophone literature limited largely to the period from 1990 to 2010 was surveyed for original research reports and review articles addressing also specifically the evidence for the consequent reductions in risk of allergic reactions and changes in the epidemiology of NRL allergies.
Glove Source Materials
Many plants produce liquid latex, but the natural material, NRL, used in rubber manufacture is almost exclusively obtained from the Hevea brasiliensis tree. It contains the rubber polymer, cis-poly-isoprene, as well as varying amounts of a large number of different proteins [20,21,22]. Various chemicals, such as accelerators, activators, anti-oxidants and vulcanizing agents, are used in the manufacture of medical gloves [[23]; for review, see [24]] but a large proportion of these chemicals are then leached out in the further stages of production, through processes such as ‘wet-gel leaching’. These leaching processes also remove the majority of the water-soluble proteins found in NRL [24].
The raw materials for synthetic glove manufacture include vinyl (polyvinyl chloride), nitrile (acetonitrile butadiene), neoprene, polyisoprene, polychloroprene, polyurethane and polyethylene, which are generally derived from oil chemistry. Nitrile is very similar in its polymer chemical structure to NRL and, in this respect, may be considered as synthetic latex.
Deproteinised latex, being composed of enzyme-treated NRL, has also been used as the source material for nitrile gloves. We are not aware of published reports in which gloves made of deproteinised NRL have been compared with conventional NRL gloves, especially with respect to their allergenic properties, although there are reports that NRL-allergic patients can tolerate condoms made from this material [26].
Recently, liquid latex from a North American and Mexican desert shrub, Parthenium argentatum, commonly known as Guayule, has been introduced as source material for gloves [27]. The obvious advantage of Guayule is that it is not botanically related to H. brasiliensis and, for the time being, no reports about type I allergies to these gloves have been reported.
Glove Properties
Barrier Properties
The primary function of gloves is to provide a competent barrier to protect against infections for both healthcare professionals and the patients. Gloves used by healthcare workers need to be single use for each patient contact and treatment, although it is recommended that prolonged and indiscriminate use should be avoided to minimize the risk of sensitization [4]. They are required in various situations such as invasive procedures and contact with non-intact skin, mucous membranes or sterile sites. As such, leakage must be minimal, even when apparently undamaged, and various standards have been developed in order that all gloves perform adequately regardless of material [4]. They should be easy to put on, comfortable to wear and provide adequate, durable protection [15].
The durability of barrier protection has been examined in a number of studies and it has been shown that NRL gloves provide lower rates of perforation and lower viral leakage rates than vinyl gloves [24,28,29]. In a study that examined gloves after manipulation to simulate in-use conditions, the failure rate was 0–4% for NRL, 1–3% for nitrile and 12–61% for vinyl gloves, indicating better barrier protection by NRL and nitrile gloves, compared to vinyl [29]. In another study where gloves were stressed according to a designated protocol before examining for leakage properties, failure rates were 2.2% for NRL and 1.3% for nitrile gloves, which were again better than for vinyl or copolymer (8.2% for each) [30]. Barrier integrity following an abrasion test demonstrated that NRL gloves were better than vinyl, although not as good as either nitrile or neoprene [31].
A study in the USA in 2004 performed post-usage examination and testing of surgeons’ gloves after routine surgical procedures. The results revealed higher after-use defects for non-latex compared with latex disposable gloves [32]. Compared with NRL gloves, the odds ratio for defects was 1.39 (95% confidence interval 1.12–1.73) for neoprene and 1.90 (95% confidence interval 1.15–3.13) for nitrile gloves. In addition, the surgeons reported significantly greater satisfaction with regard to factors such as quality, safety and durability for latex compared with latex examination gloves. These results should probably be treated with caution because the surgeons had never used non-latex gloves before for routine surgery (acknowledged by the authors as a possible bias) and only 215 nitrile gloves were used compared to 2,647 latex and 3,624 neoprene gloves. In addition, the main difference in the study was in visible leaks, with no significant difference in water leaks, which may be explained by the low tear propagation strength of nitrile/neoprene. Similar differences between neoprene and NRL have been demonstrated in another study [33] where it was noted that punctures in neoprene gloves were detected more readily by surgeons than punctures in NRL gloves.
A recent study [34], comparing synthetic polyisoprene and NRL gloves during heavy orthopaedic surgery with high risk of perforations, revealed a significantly higher perforation rate in latex-free gloves (80.0%) compared with NRL gloves (34.4%). Again, the study was poorly controlled and open to criticism because glove usage was not randomized, being based on two surgical teams in two different hospitals, one using NRL, the other using polyisoprene. It is, however, interesting that these three studies appear to detect highly significant differences in perforation rates between NRL and non-NRL [32,33,34].
Fit and Comfort
According to the Scientific Committee on Medicinal Products and Medical Devices of the European Commission [35], nitrile gloves are usually of lower tensile strength than surgical gloves, but their elastic modulus, or stiffness, is somewhat higher. In addition, nitrile has a higher permanent set than latex, meaning that once stretched it does not fully recover. Thus, nitrile gloves tend to be designed to fit more loosely than latex, and the combination of these properties may affect the users’ tactile sensation and delicacy of touch. This has been confirmed by a study [36] where participants noted that nitrile gloves that fitted their fingers were too narrow for their hands and gloves that fitted their hands were too large for their fingers. During this research, it was confirmed that there are detectable differences between nitrile and latex, where a pegboard test demonstrated an 8.6% increase in fine finger dexterity for latex over nitrile, although no differences related to gross dexterity. Whilst it is not clear at present what the practical effects of this research mean, it does appear that the stiffness of nitrile may affect user dexterity. The study also questioned users about their preferred material, with 67% preferring latex and 21% preferring nitrile.
Thus, a variety of factors, including glove strength, abrasive resistivity, dexterity and comfort, should be taken into account when selecting gloves for specific needs.
Enhanced Barrier Performance by Means of Double Gloving
When carrying out operations, perforations in gloves often go unnoticed and there is frequently a risk of contamination and exposure to blood-borne pathogens [37,38].
As a result, double gloving has been routinely used by a proportion of surgeons since the early 1990s. However, double gloving is reported to be less common in the UK, Europe and the USA than in other countries, except in the areas of orthopaedics and maxillofacial surgery [38,39]. Double gloving is generally carried out with two layers of NRL gloves [38], although sometimes the inner glove can be synthetic, which may reduce the risk of allergic reactions.
