Medical Glove Safety - Technical Overview for the JOWC (1996)
Pete Phillips, SMTL
Despite the problems experienced with latex gloves over the last few years, latex is still the preferred material for glove manufacture.
This article will explore the methods of manufacture of latex gloves, highlighting processes that may have an adverse or beneficial effect on the final product.
In addition, the issues of safety testing gloves will be examined, in particular tests for allergens and proteins.
Finally, new techniques for manufacturing latex gloves and alternative materials will be explored.
Latex is the protective fluid contained in tissue beneath the bark of the rubber tree,Hevea brasiliensis.
The tree originated from Brazil (hence its name), and latex was originally gathered from wild trees in the jungles of Brazil in the 1870's. By 1890, Britain had introduced rubber plantations in Malaysia (with the help of Kew gardens and the Singapore Botanical Gardens) and was harvesting latex.
Natural rubber latex (NRL) is a cloudy white liquid, similar in appearance to cows milk. It is collected by cutting a thin strip of bark from the tree and allowing the latex to exude into a collecting vessel over a period of hours.
The composition of the latex is detailed in table 1
Table 1: Composition of Latex Sap.
|Rubber particles (cis-1,4-polyisoprene)||30-40%|
This solidified rubber is also known as crepe.
Initially, the rubber had to be solidified within 24 hours to stop bacterial spoilage. In the 1920's it was discovered that the addition of ammonia could preserve the latex. Table 2 below shows the latex glove manufacturing process in detail and highlights the effect of each step on the amount of Type I and Type IV allergens in the latex. Clearly, the amounts of protein (the cause of Type I allergic reactions) and various chemical additives (some of which may cause Type IV allergic reactions) vary throughout the manufacturing process, and can be controlled by careful processing.
The latex glove manufacturing process is a complex multi-stage process, during which the raw material undergoes many physical and chemical operations.
Table 2 below details the different stages of glove manufacturing and the effect of each process on substances which can cause allergic reactions - a plus (+) indicates an increase in these substances while a minus (-) indicates a reduction.
Table 2: The Latex Glove Manufacturing Process.
|Stage||Type I Allergy||Type IV Allergy|
|Harvesting of Latex.||Â||Â|
|Addition of preservative||--||+|
|Lubrication or chlorination.||+ or -- (see text)||Â|
- Harvesting of Latex: In this process, the rubber tree is tapped for the milk-like latex.
- Addition of preservative: Ammonia along with a small amount of thiurams is added to stop microbiological spoilage and curdling of the latex. Ammoniation can, if performed at the right time, aid in the hydrolysis of proteins.
- Pre-Centrifugation: Some manufacturers areÂ experimenting with the addition of proteolytic enzymes prior to centrifugation to break down proteins in the mix, and reduce the amount of available proteins in the final product. Enzymes can significantly reduce protein levels, but some authors believe they may also adversely affect the mechanical properties of the latex film.
- Centrifugation: Centrifuging the latex concentrates the rubber content up to about 60%, but also reduces the protein content. Double centrifuging can reduce protein content even further.
- Compounding: At this stage, up to a dozen chemicals are added, including accelerators (which help control the later vulcanisation process) and antioxidants (which prevent deterioration of the rubber molecules in the final product by heat, moisture and ozone). Accelerators (thiurams, mercaptobenzothiazole, carbamate, thioureas) are well known as Type IV allergens. Thiurams are well known as sensitising agents and many manufacturers now replace thiurams with dithiocarbamates as the accelerators of choice.
- Dipping & Coagulation: The hand-shaped formers are coated with coagulant (e.g., calcium nitrate) and dipped into the latex to coat them with a thin film of latex. The coagulant converts the liquid latex film into a wet-gel on the former. Subsequent passage through a warm oven completes the coagulation process.
- Pre-vulcanisation leaching: Also known as "wet gel leaching", this is the process of immersing the latex-coated formers into a bath or spray of water, to wash out excess additives from previous stages, such as coagulant. Chemical and protein content can be reduced at this stage. The effectiveness of the process is dependent on the temperature of the water, the duration of the process, and the rate of water exchange.
- Vulcanisation: Vulcanization was one of the key discoveries in the manufacture of rubber products. In this stage, the latex film is heated, and the combination of sulphur, accelerator and heat cause cross-linking of the rubber, giving strength and elasticity to the film.
- Stripping: Vulcanization was one of the key discoveries in the manufacture of rubber products. In this stage, the latex film is heated, and the combination of sulphur, accelerator and heat cause cross-linking of the rubber, giving strength and elasticity to the film.
- Post-vulcanisation leaching: Also called "dry-film" leaching, this process is similar to the wet-film leaching above, except it is carried out on the dry/vulcanised latex film. The effectiveness of this process in reducing water extractives is a function of time and temperature. Some manufacturers leach the gloves at this stage for up to 24 hours.
- Lubrication: Hydrolysed corn starch is added as a lubricant, to enable easy donning of the glove by tumblng the gloves in a slurry of starch and biocide. Starch has been shown to bind to the latex proteins, and act as a vector for transfer of the protein to the skin or to the lungs (as an airborne dust) which can cause asthma (see later for a fuller discussion of starch powder).
- Chlorination: Instead of powdering, some manufacturers dip their gloves into a chlorinated solution (for example, sodium hypochlorite acidified with hydrochloric acid). This makes the glove surface slippery, and therefore negates the requirement to add a powdered lubricant. Chlorination has been shown to substantially reduce protein levels in latexÂ Citation:Dalrymple Audley Rubber Developments 1992 but excessiveÂ chlorination can also adversely affect the physical properties of the latex (tensile strength, elasticity)
- Checking: In some plants, the gloves undergo 100% testing by air inflation. In addition, some gloves will be removed and tested by the water method (which is a more sensitive test, and part of the European standardÂ Citation:EN 455-1 1994 ) for pinholes as part of the routine quality assurance process. Other tests will also be performed, such as tensile strength tests.
- Packaging: This is the last stage before the gloves are distributed to the user.
The naturally occurring proteins are present either as water soluble (and therefore extractable) protein, or as "bound" protein - protein which is bound to the rubber molecules. Amongst these proteins are the enzymes involved in the biosynthesis of the rubber itself.
Some proteins are useful in latex manufacturing. In particular, those proteins associated with the rubber are important in maintaining the colloidal stability of the latex, but those found in the aqueous phase (also called the "serum") are thought to have "little technological significance" Citation:Pendle 1992 Maryland Conference sensitivity latex
Those proteins associated with the rubber molecules are insoluble, and therefore non-extractable. They cannot usually be leached from the latex while it is being worn, and thus are unable to cause an allergic reaction. Footnote:
It is possible to inadvertently increase the amount of extractable protein by the addition of detergents or potassium hydroxide which disassociates the protein from the rubber molecules. Citation:hamann kick cutis 1993
Because some protein is "extractable" by aqueous methods, it has generally been accepted that moisture on the skin (sweat) can extract the protein from the glove and onto the wearers skin, where it can cause a Type I allergic reaction in sensitised individuals. The rapid reaction of a patient to direct tissue contact with a latex glove suggests that the proteins are released upon contact, and that neither sweating of the hand nor prolonged exposure is necessary to liberate the proteins from surgical gloves. Citation:Fay Regent Issues latex safety medical environment
The route of exposure is particularly important in determining the extent of the reaction. For example Citation:Sussman Allergy Proc 1992 latex allergy importance clinical practice
Cutaneous exposure can cause itching, eczema and dermatitis,
Airborne exposure can cause rhinitis, conjunctivitis and asthma,
Mucosal and parenteral exposure may lead to anaphylaxis.
In the USA a number of cases have been recorded of death from anaphylaxis during barium enema procedures due to Type I reactions to the latex cuff on the rectal catheter.
Other latex medical and non-medical products may cause sensitisation to latex proteins, including
Rubber dental dams
Rubber toy balloons
It is worthwhile noting that products made from dry rubber (that is, the latex is coagulated, "crumbled", washed and dried) have extremely low levels of extractable protein Citation:Yip Turjanmaa Ng Mok J. nat Rubb Res 1994 allergic responses extractable proteins and very low or negligible allergenicity, probably due to the high temperatures achieved during the moulding process.
Proteins and Glove Powder
When surgical gloves were first introduced, the gloves were sterilised by boiling and then put on wet over wet hands. Citation:ellis 1990 hazards of surgical glove dusting powders
With the introduction of dry sterilisation, a dusting powder was necessary to facilitate donning of the glove. Originally, talc was used, but by the early 1940's it was recognised that talc caused granulomas and adhesions. Corn starch treated with epichlorhydrin was found to be a good alternative. This corn starch powder (mixed with 2% magnesium oxide to act as a dessicating or "anti-caking" agent) became known as absorbable dusting powder (BiosorbÂ®), and is still in use today.
Starch, granulomas and adhesions.
The absorbable dusting powder was expected to be harmlessly absorbed by the body (as predicted by the original animal experiments), but in 1955 came a report of two patients with wound granulomas caused by corn starch. Citation:Snierson Woo 1955 Starch Granuloma Subsequently much evidence has been accumulated to show that corn starch causes a range of post-operative problems, including adhesions, granulomas and starch granulomatous peritonitis. From this evidence it became clear that starch powder had to be removed completely from the surface of the glove before use to prevent migration of starch into the patients wounds or body cavity.
Starch and its relationship to hypersensitivity.
Even so, the general consensus was still that starch did not present a hazard to glove users, but in the mid 1970's a series of experiments were performed which showed that delayed hypersensitivity to starch could be induced in guinea pigs. Human patients were also shown to have developed hypersensitivity to starch Citation:grant davies espiner 1982 but reported cases are rare. Many users believe the reactions they experience from a latex glove are due to the powder, but this is rarely the case. The majority of glove reactions are Type IV (delayed-type) allergy, usually from accelerators. Immediate-type allergies occur less frequently, and are usually initiated by latex proteins, but accelerators have also been shown to induce glove-related immediate-type allergies. Citation:Heese Hintzenstern Peters Koch Hornstein 1991 Although glove powder has been reported to be the cause of several cases of immediate-type reactions, Heese et al Citation:Heese Hintzenstern Peters Koch Hornstein 1991 believe that the observed incidences have been due to the presence of proteins in the powder. They also note that epichlorhydrin and sorbic acid (found in some glove powders) are known Type-IV allergens. Glove powder can also provoke irritant reactions by mechanical means, especially in atopic patients.
The usual method of applying the powder is by immersing the gloves into a slurry of the powder. It is now clear that during this process proteins can be leached from the latex and deposited in the slurry mix. Citation:Esah Yip Mok Ng production of natural rubber low extractable protein 1994 The advantage of this is that the extractable protein in the glove can be reduced further. However, there is a danger of protein build up in the slurry tanks themselves, which can lead to deposition of protein back onto the gloves.
Of particular concern is the observation that the starch binds the allergenic latex proteins. Thus corn starch powder does not generally cause an allergic reaction on its own, but by binding with the latex proteins it provides a vector for transferring the protein to staff and patients as follows:
Aerosolisation of the powder and subsequent inhalation - when users don a pre-powdered glove, the powder can be released into the air where it can be inhaled. The bound protein can cause a range of allergic reactions such as asthma and conjunctivitis.
Mechanical abrasion of the users skin - the starch particle can abrade the users skin, transferring the bound protein directly into the abrasion.
Transfer of the powder to the body cavity of the patient - complete removal of powder is extremely difficult, and medical staff may transfer the powder-protein complex directly into the patient during treatment.
Starch as a vector for pathogens.
There is also growing evidence that glove powder can act as a vector for pathogens, Citation:Newsom Shaw Airborne particles Heathrow and investigations are now being mounted into the possibility that glove powder in clinical areas can lead to an increased risk of post-operative infection. Podell Citation:Risks Complications Podell Regent notes that where glove powder is used, "it can be found throughout the operating theatre, acting as a magic carpet for microorganisms to contaminate the surgical field; it is attracted electrostatically to instruments, needles, sutures and implants, and is not removed by routine washing and wiping."
Chlorination of the latex glove reduces the stickiness of the latex by modifying the rubber surface. This produces a smooth, non-tacky surface on the glove, which can be donned without the aid of dusting powder. An added benefit of chlorination is that it reduces the amount of extractable protein in the glove, either by denaturing the protein or by leaching. Dalrymple and Audley Citation:Dalrymple Audley 1992 Rubber Developments have shown that the effectiveness of the chlorination procedure in reducing extractable protein levels probably results from exposure of the latex to the water, salt, acid and ammonia associated with the process and not from the chlorination itself.
Hydrogel coated gloves (such as BiogelÂ®) eliminate the need for powdering as the hydrogel creates a slippery surface on the inside of the glove which aids donning. The hydrogel may also act as a barrier between the users skin and the latex, thus reducing the exposure to the latex proteins. An antiseptic coating on the Biogel glove (cetylpyridinium chloride) bound to the hydrogel may also act as an antiseptic barrier to cross-infection if the glove is punctured. Citation:Podell 1989 search for a safer glove Risks and complications
Testing for Proteins.
There are two reasons to test for proteins or protein allergens:
To determine whether a user or patient is allergic to latex gloves. These tests are covered in the article ____ by ____ in this supplement.
To determine whether a particular glove or brand of gloves is likely to cause sensitisation of non-allergic individuals or an allergic reaction in previously sensitised individuals.
Users and purchasers of gloves should have two aims in mind when considering the protein allergen issue:
To reduce the numbers of individuals sensitised to latex proteins,
To avoid eliciting allergic reactions in individuals already sensitised to latex proteins. Previously sensitised individuals can have an allergic reaction provoked by much lower levels of protein than is required to sensitise in the first place.
Table 3 details the advantages and disadvantages of each test.
Table 3: Tests for allergenic protein in latex gloves.
|Skin Prick Test (SPT)||Specific for allergens. Very sensitive. The "ultimate" proof of allergic reactions in-vivo. Good correlation with RI and EI methods.||Requires NRL sensitised individuals who are willing to be tested, therefore not acceptable for routine use. It is dependent on the subject having been sensitised to the allergens in the latex and on the degree of sensitivity of the individual.|
|Total Extractable Protein (TEP)||Correlation with SPT quite good. Reproducible. Stable reagents and colour. Relatively easy to perform.||Non-specific - detects all proteins, not just allergens. Comparatively insensitive c.f. immunoassay methods. Susceptible to interfering substances - for example, surfactants can produce lower than expected readings while accelerators can produce higher readings.|
|RAST Inhibition (RI)||Sensitive, reproducible and specific - only measures allergens. Readily available (widespread). In-vitro compared with SPT which is in-vivo.||Depends on pooled human sera for the antibodies. Time consuming and expensive. Pooled sera must include all relevant antibodies. Requires handling of radioactive reagents. Less sensitive than the SPT - generally accepted to detect only 50-60% of latex sensitive subjects (but claims have been made for up to 94% sensitivity with some recent assays) Citation:Keith Amsterdam Conference 1996 occupational health|
|ELISA Inhibition (EI)||Good correlation with SPT and RI. Simple No radioactive reagents required. Automation possible, therefore relatively cheap. Readily available (widespread technique). In-vitro c.f. in-vivo SPT.||Depends on pooled human sera for the antibodies (as with RI). Pooled sera must include all relevant antibodies. Difficult to standardise. Less sensitive than the SPT - generally accepted to detect only 50-60% of latex sensitive subjects.|
|LEAP||Very sensitive c.f. TEP. Less susceptible to interfering substances c.f. TEP. Specific for latex proteins.||Measures antigens not allergens, therefore is a form of TEP. Difficult to standardise. Reproducibility unclear.|
|Immunoblotting||Useful R&D technique.||Qualitative (not quantitative). Insensitive to small molecular weight peptides.|
|Immunospot||Simple||Semi-quantitative only. Relatively insensitive. Time consuming. Difficult to standardise.|
|Electrophoretic Methods (e.g., RIE/RRIE & CIE/CRIE)||Differentiates between antigens and allergens. Useful research tool.||Requires rabbit serum with relevant antibodies. Time consuming. Research purposes only.|
The Skin Prick Test
The Skin Prick Test (SPT) provides the ultimate proof on whether the extract from a glove will elicit an allergic reaction in an individual, as it is performed in-vivo. Unfortunately, for this very reason, it cannot be used routinely as a test for identifying gloves with high levels of extractable allergens, but is extremely useful as a research tool in validating other in-vitro tests.
Total Extractable Protein
The "total extractable protein" (TEP) assay (also commonly known as the "modified Lowry" method) measures the total amount of protein in an extract made from the glove, and is presently being considered as the standard test method for measuring protein levels in gloves for Part 3 of EN-455 Citation:prEN 455-3 (the European standard for medical gloves). Whilst is can be criticised for measuring all the extractable protein in the glove (and not just the allergenic proteins which cause the Type I reaction) it appears to be a useful indicator of whether the gloves are likely to produce Type I reactions. Yip et al Citation:Yip Turjanmaa Ng Mok 1994 show that there is quite good correlation between TEP and allergic reactions in individuals showing latex hypersensitivity. Whilst it has not yet been possible to determine a threshold level below which a latex sensitised individual will not experience an allergic reaction, their data demonstrates that at TEP levels of 400 Âµg/g, only 60% of the 59 latex sensitised subjects experienced an allergic reaction. They conclude that for even higher negative responses, TEP content should preferably be less than 100Âµg/g.
Immunogenic Assays (RI & EI)
RAST Inhibition and ELISA Inhibition assays are quantitative assays which measure the allergen content of the gloves, and so are more specific tests than TEP. There are, however, a number of problems with using these tests as routine screening tests for latex gloves, mainly related to the necessity for a source of pooled sera from latex hypersensitive individuals. These tests also have to be validated against in-vivo methods to show that the allergens being measured are able to elicit a Type I response in sensitised individuals.
Is it possible to identify a "safe" level of protein in latex gloves ?
The main problem at present is that we do not know exactly which proteins cause Type I allergy. Whilst TEP results can give a good indication of the likelihood of a glove causing a hypersensitivity reaction, Citation:Yip Turjanmaa Ng Mok 1994 there is a theoretical possibility of a glove containing extremely low levels of proteins, where all of those proteins are allergenic and likely to cause a Type I reaction. Conversely, it is also possible that gloves low in allergen content may be high in TEP (Yunginger et al Citation:Yunginger 1994 Allergy Clin Immunol reported such a case where non-latex protein was added to the glove during manufacture).
The Food and Drug Administration (FDA) in the USA stated in March 1995 Citation:FDA March 1995 interim guidance on protein content latex medical gloves that
"Although there are insufficient clinical data to set a protein level that dramatically reduces the incidence of reactions to latex protein, there is scientific consensus that reduced protein levels will lower the potential for both sensitisation of non-sensitised individuals and allergic reactions in sensitised individuals."
The FDA now have a policy of
allowing manufacturers to label their gloves with a specified protein level (based on their maximum process level, not the average figure),
making it mandatory for manufacturers who include TEP figures to also include a statement as follows (unless clinical evidence can be submitted to verify the claims):
"Caution: Safe use of this glove by or on latex sensitised individuals has not been established."
not allowing products to be labelled with TEP levels lower than 50 micrograms per gram as this is the sensitivity limit of the ASTM Lowry test method (which is very similar to the proposed CEN method).
The FDA has also proposed a ban on the use of the term "hypoallergenic glove" until it is properly defined. Some manufacturers use the term to refer to the fact that their gloves may contain reduced levels of chemical additives, or the fact that they use carbamates instead of thiurams as accelerators. Even so, these gloves may contain the same or higher levels of TEP than gloves not so labelled. Citation:Keith Amsterdam 1996 Others base their "hypoallergenic" claim on the results of modified Draize testing Citation:Yunginger Allergy Clin Immunol 1994 which is not an appropriate measure of the the ability of a product to induce a human IgE antibody response. The Canadian Medical Devices Bureau have suggested that a level of 50 nanograms/gram of TEP would be required for a truly hypoallergenic latex device.
It is clear that TEP levels are useful in guiding purchasing decisions, but for the moment there is no consensus on a minimum acceptable level. This situation is likely to change in the future as the allergenic proteins are identified, which will enable the development of tests specific for the known allergens. Already there is good evidence for a number of "marker" proteins known to cause Type I allergies. Citation:Czuppon Allergy Clin Immunol Nov 1993 Citation:Akasawa Hsieh Lin Serum reactivities to latex proteins Allergy Clin Immunol 1995 Citation:Beezhold Sussman Kostyal Chang latex protein 1994
There are a number of alternatives to latex for the manufacture of gloves, but none of them have the same unique combination of properties as latex. The following lists alternative materials along with their advantages and disadvantages. Citation:Lyszkowski Amsterdam Conference 1996 Citation:Morris health considerations of synthetic alternatives to natural rubber latex 1994
Plasticised PVC - usually only used for examination gloves, PVC is cheap, but has poor elasticity and tear strength, and there have been reports of allergic reactions to additives from the manufacturing process. Citation:Estlander Jolanki 1986 Contact Dermatitis Disposal of PVC by incineration is known to release the monomer vinyl chloride, a known human carcinogen. PVC will tend to have higher levels of chemical additives than latex.
Nitrile & Neoprene (polychloroprene) are similar to natural rubber when vulcanised, but their tensile strength is usually lower whilst their elastic modulus tends to be higher (leading to finger fatigue over time). Incineration of both can lead to the release of hazardous chemicals, such as cyanide from nitrile and hydrogen chloride from Neoprene. Citation:Morris health considerations of synthetic alternatives to natural rubber latex 1994
Copolymer film gloves are not an acceptable substitute for NRL gloves, as they have reduced tear strength, and have been shown in the laboratory (SMTL Welsh NHS contract testing, unpublished) to be unsuitable for rectal or vaginal examinations due to bursting of the seam. They have a very limited field of use.
Styrene Block Copolymer - can be manufactured into gloves strong enough for medical use, but their poor ability to return to their original shape after repeated stretching is worse than that of NRL gloves. It has been reported that styrene can cause Type I allergic responses, Citation:Moscato Biscaldi Cottica 1987 but there is little evidence at present on how well tolerated these products are due to the small numbers being used.
Polyurethane - can be used to manufacture very high tensile strength gloves, but its modulus of elasticity and elongation at break can make the gloves uncomfortable to wear. There have been reports of reactions to polyurethane implants Citation:Berrino Galli Rainero 1986 but LRC Citation:Lyszkowski Amsterdam 1996 claim that polyurethane can be made into very clean medical devices, with low levels of extractables, irritants and allergens, which is why they chose it for their AvantiÂ® condom. Polyurethane gloves also tend to be very expensive.
Whilst latex-free gloves may be more expensive than the latex alternative on a unit basis, the cost disadvantage may be outweighed by the potential reduction in costs of dealing with latex allergy. Nevertheless, it can be seen that it is difficult to find an alternative to latex that matches it in terms of its physical properties (high tensile strength, softness, excellent film-forming properties). As latex has been used almost universally for such a long time, there is a considerable body of evidence on the likely ill-effects of latex medical devices. Whilst Morris Citation:Morris health considerations of synthetic alternatives to natural rubber latex 1994 states that alternatives to latex gloves should be available for sensitive individuals, he does not believe that a wholesale move to non-latex gloves will be risk free, and that it would result in the majority of users (who do not experience any ill-effects from latex) having to use an inferior performing glove.
Although latex proteins have been the focus of this supplement, there are many other parameters involved in glove safety, as can be seen in Table 4
Table 4: Glove Safety.
|Barrier Properties||European standard EN-455 Part 1 Citation:en 455-1 details the test method (1 litre water test) and the limit (AQL of 1.5%) for perforations in gloves. There is also evidence to show either that HIV does not appear to leak through latex films or that the leakage is only detected with a very high challenge Citation:Carey Herman Retta Sex Transm Dis 1992 Recent press reports of viral penetration of some brands of latex surgeons gloves versus other brands have not yet appeared in a referred journal and should, for the moment, be treated with caution.|
|Strength||EN-455 Part 2 Citation:en 455-2 details the test method for force at break of medical gloves, including limits for different types of gloves. Interestingly, the limits for synthetic gloves are lower than those for latex gloves.|
|Protein levels||Draft EN-455 Part 3 Citation:pren 455-3 includes a test method for TEP but does not specify a limit. It will probably request manufacturers to monitor the amount of TEP in their gloves, and to make test results available on request. As the field matures, it is expected that limits for TEP will be agreed.|
|Other Biological risks.||EN 30993 sets out specific test methods for the biological evaluation of medical devices and includes a section which helps determine what tests should be performed for certain types of devices. In addition, draft EN-455 Part3 Citation:pren 455-3 requires that the manufacturer provides the consumer on request with a list of chemicals determined as being bioavailable in the finished product.|
|Pyrogen and Endotoxin content.||Endotoxin is the cell wall of gram-negative bacteria. Pyrogens are substances which can cause fever, such as dead bacteria, viruses, yeasts and molds. Sterilisation does not inhibit the effect of these substances, and both have been shown to cause allergic dermatitis on the surface of the hand. However, the more serious consequences occur if they find their way into blood or tissues. These include fever, inflammation, complement activation, cell lysis, vascular necrosis, macrophage activation etc. Citation:Truscott Amsterdam 1996 The draft EN-455 Part 3 Citation:pren 455-3 quotes the test method for endotoxin testing as the European Pharmacopoeia test for bacterial endotoxin. Citation:Ph Eur Test for bacterial endotoxin The standard states that if a manufacturer labels sterile gloves as "Low Endotoxin Content" then the upper process limit, as determined by the above method, should be part of the glove labelling.|
|Grip||Perhaps the grip of a glove may not be thought of as safety related, but clearly the ability of the user to carry out a task should not be hindered by a glove which is too tacky or slippery. There is no standard dealing with this aspect of medical gloves, although it is clear that glove grip has a major impact on glove selection by the medical and nursing profession. The other side of the "grip" coin is the ease of donning. Some gloves are given a special treatment on the inside of the glove during manufacture to enable easy donning of the glove without the need for powder (for example BiogelÂ® gloves) which does not affect the "grip" on the outside of the glove.|
|Glove stiffness.||Glove stiffness is related to the elasticity of a glove. If the latex is not elastic enough, then the glove will not conform to the hand. Too stiff, and the users hand will experience fatigue over prolonged usage. There is no standard covering this aspect of medical gloves.|
|Chemical Barrier Properties and Cytotoxic permeability||Gloves are frequently used during the reconstitution of cytotoxic preparations. Different gloves have differing permeation rates when tested against various cytotoxic drugs. Citation:Fenton May Thomas 1987 carmustine exposure Citation:dinter-heidorn carstens cytotoxic gloves Citation:slevin johnston turner cytotoxic gloves An appropriate choice can only be made based on knowledge of how the substance in question permeates the glove and how long the glove is likely to be in contact with the substance.|
|Glove Powder||(See main article for discussion of the role of powder in conjunction with protein in gloves). Powder is increasingly thought to be a potential hazard in healthcare, as a vector for transport of latex proteins or for infective organisms. There is no standard covering the requirements of powder, except a BP standard for the powder itself and a requirement in the draft EN-455 Part 3 Citation:pren 455-3 that all powdered gloves carry a warning to users to remove all powder prior to undertaking operative procedures. LRC recently organised a conference (Heathrow, May 18th 1996) on the hazards of glove powder, the thrust of the conference being that evidence is mounting on the potential hazards of glove powder and that a ban should be considered. Whilst this may be an extreme point of view at present, it certainly reflects growing concern over glove powder in the health care environment.|
So how can a user or purchaser make sense of a manufacturers claims ? It is not a trivial matter. M. Fay Citation:Fay Amsterdam Conference 1996 states that selection criteria should be used to identify known risk factors, and then glove features selected that minimise those risk factors and increase the chances of positive patient, worker and institutional outcomes. Gloves can be screened by collecting and evaluating evidence based on the factors in table 4 above. Fay proposes that potential purchasers ask the following questions:
Is the product safe ? Does it meet regulatory criteria (for example, does it comply with EN-455 Part 1 and 2) ?
Does it fulfill its intended purpose ?
Is the product better than a currently stocked item ?
Are product claims supported by independent testing laboratories or clinical research published in a referred medical journal ?
Can the increased cost for the products be offset by proven savings from risk reduction ?
The Department of Health have recently published a device bulletin on latex sensitisation Citation:MDA latex sensitisation health care April 1996 which contains some useful advice on glove selection and includes an outline policy which should be implemented in health care establishments.
By understanding the process of glove manufacture and the key safety parameters, it should thus be possible to determine whether the gloves on offer are acceptable or not. In the future further advances in latex and synthetic glove manufacture can be expected (such as fumed silica latex Citation:Anand Amsterdam 1996 fumed silica and highly deproteinated latex Citation:Nakade low-allergen NR products ) which will produce gloves with negligible allergen content and improved physical and mechanical properties.
I would like to thank Mr Ray Russell-Fell, rubber consultant, for technical information on latex manufacture and for reviewing this article. All errors and omissions are, however, those of the author.