Abstract
Aims To compare blood transmission through nitrile, single and double layer latex glove materials in simulated needlestick injuries.
Methods Experiments involved nitrile, single and double layer latex gloves. A cutting suture needle was dipped into a specimen of blood and then immediately jabbed through the glove material into a cell containing saline. This process was repeated using the same blood specimen with different glove materials, plus a control experiment with no glove material. Other factors, including the angle, speed and depth of needle penetration, were controlled through the use of a testing machine. Following needle punctures, samples were taken from the suspension contained in each cell and examined under blind conditions. Median red blood cell (RBC) count was used as a measure of the quantities of blood transmitted through the different gloves.
Results Nitrile glove material was associated with reduced transmission of RBCs compared to single layer latex. Double layer latex gloves provided better protection than single layer latex or nitrile gloves.
Conclusions These findings suggest that in protecting against blood transmission in the context of needlestick injuries, single layer nitrile gloves are superior to single layer latex gloves, but double gloving with latex gloves provides better protection than either single layer latex or nitrile.
Discussion
Our study found that the wiping quality of nitrile glove material was modestly superior to single latex material and that double layer latex gloves provided better protection than single layer latex and nitrile gloves. To the authors’ knowledge, this is the first experimental study using a computer-controlled system to produce simulated needlestick injury.
Nitrile is associated with promising biomechanical performance and has been recommended as an alternative to latex [13]. Nitrile is made by polymerizing monomers, which contain triple carbon–nitrogen bonds (nitrile functional group). Natural rubber latex is a diene polymer made from monomers containing carbon–carbon double bonds which crosslink one polymer to another. This provides latex with a superior elastic character to most synthetic rubber materials. The dynamic properties of latex produce a greater ability to reseal puncture holes and significantly reduce the leakage of fluid after the material is perforated with a needle [14]. The existing evidence shows that majority of glove perforations go undetected [15]. It is therefore likely that nitrile gloves, which have less ability to reseal puncture holes, would carry a greater risk of blood transmission through perforation.
It has also been suggested that this inherent quality of latex could offer a better wiping effect. However, the findings of this study do not support this view. Due to its different characteristics, nitrile material is more resistant to abrasion and puncture than latex [13]. Besides its other physical and mechanical properties, the greater stiffness and the coarse surface of nitrile may influence the wiping effect.
Our literature search shows that there is limited published evidence on the wiping effects of latex and nitrile gloves in simulated injury. In the study by Mast et al [3], a limited number of observations were undertaken and the power of the study was low. Their experiments did not detect a statistically significant difference between the wiping effect of latex and of nitrile materials. In contrast, the current findings show a statistically significant difference between latex and nitrile gloves in needlestick simulations with a suture needle.
Cumulative evidence supports the practice of ‘double gloving’ [16]. There is also interest and debate on the selection of latex glove substitutes [17]. The difference observed in this study between single and double latex gloves in needlestick injury with a cutting suture needle is consistent with previous studies [10]. Additional protection associated with double latex was reported by Bennett et al. [10]. This was also supported by an experiment with an enzyme solution described by Lefebvre et al. [11]. However, two other studies by Bricout and Krikorian suggest double layer latex gloves offer little benefit over single layer latex gloves [5,18]. The study design and methodology of these experiments probably influenced the results. Given the mechanical characteristics of blood removal by barrier gloves, an enhanced wiping effect of double layer gloves is likely. ‘Double gloving’ is reportedly associated with diminished tactile sensation and reduced dexterity. On the basis of objective measurements, the perceived impact of double layer gloves on dexterity does not appear clinically significant [16].
This study has a number of strengths. First, the computer-controlled system provides reproducible simulated needlestick injury with controllable parameters. Second, the large number of observations for each experimental condition provides sufficient statistical power to control type II errors and detect differences between glove materials.
We acknowledge that this study has some limitations. Firstly, in the present work, only non-sterile gloves were tested. Although it is plausible to extrapolate the results of the present paper to sterile gloves of comparable thickness, the wiping effect of sterile gloves may be an area that deserves further investigation.
Secondly, this study used a specimen of horse blood as an available alternative to human blood for the test contaminant and made use of RBC count as a surrogate marker of viral transmission. Comparisons have shown similarities between haematocrit and whole blood viscosity in horses and humans [19], which are expected to influence its adherence to a needle or glove [9]. Moreover, in the present study, comparisons were made using the same sample of blood throughout the experiment and it is therefore considered unlikely that the use of horse blood significantly influenced the results. Experiments using human blood with techniques for measuring BBV transmission are recommended for future studies.
Free viruses such as hepatitis B virus and hepatitis C virus are randomly dispersed in samples of blood from infected patients. HIV viruses can be carried in infected circulating cells (e.g. T cells), which are also distributed at random in a blood specimen. It is therefore reasonable to conclude that the volume of blood inoculum transmitted correlates with the number of viral particles, which is a major determinant of the risk of infection.
From the findings of this experiment, greater protection is expected with two layers of latex compared to one layer latex or nitrile gloves, supporting the practice of double gloving in high risk medical procedures.
Existing evidence tends to suggest that nitrile gloves have less ability to reseal puncture holes and in theory, this would make the use of nitrile gloves less advantageous [14]. However, the present study indicates that the wiping quality of nitrile glove material is modestly superior to single latex material.
Future studies should attempt to represent actual needlestick injuries in clinical practice with methods measuring viral burden of BBVs transferred. Further investigations with double nitrile gloves are recommended to indicate whether these are equivalent or superior to double latex material.
Key points
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There is limited evidence to assess the effectiveness of different glove materials in reducing the risk of transmission of blood-borne viruses associated with needlestick injury.
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In the context of protecting against blood-borne viruses transmission in needlestick injuries, single layer nitrile gloves seem to be modestly superior to single layer latex gloves.
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Double gloving with latex gloves provides better protection against red blood cell transmission in needlestick injuries than either single layer latex or nitrile.
The authors would like to thank all the personnel at the Surgical Material Testing Laboratory, Bridgend, UK. This work is attributed to Occupational Health Department, Princess of Wales Hospital, Bridgend, UK.
