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A recent Cochrane systematic review suggests that the use of double gloves reduces the risk with more than 60%
Christina Mischke MSc
Jos Verbeek MD PhD
Finnish Institute of Occupational Health,
The use of gloves is mandatory in many medical procedures for good reasons. Gloves protect the hands of the healthcare worker from potentially contaminated blood or other bodily fluids and gloves reduce hospital infections.1
Disposable gloves work as a physical barrier to prevent direct skin contact when touching surfaces, handling instruments or examining patients. They get thrown away after use and are made out of different polymers such as latex, nitrile rubber, vinyl and neoprene. Medical gloves can be sterile or unsterile, with or without cornstarch powder for easier donning, and they come in different colours and sizes.
During surgical procedures gloving is routine practice, not only to ensure a sterile environment when operating but also to protect the workers. Every worker in the operating theatre (surgeons, scrub nurses and assistants) risks contact with blood or other bodily fluids that could be possibly infectious, either due to direct patient contact or when handling the sharp instruments. Sharps such as needles can perforate gloves and puncture the skin of the glove wearer resulting in a needle stick injury. In both cases, the protective barrier is broken and there is a risk of infection.
For employers, it is mandatory to protect workers against the occupational risk of infection with contaminated blood based on a special EU directive. Extra gloves could help. An extra pair of gloves has been shown to provide increased resistance to needle penetration in the laboratory. Laboratory experiments have also shown that, when there is a perforation, the extra glove wipes off more fluid from the needle than a single glove.2,3
However, double gloving is not yet a standard for all medical procedures that involve a risk of needle stick injuries. This could have two reasons. Workers are not convinced that double gloving works and they are concerned that it decreases hand sensation.
Therefore, we performed a Cochrane review to find out if double gloving also works in practice and what are the exact benefits and drawbacks.4
How do we know that double gloving works?
The easiest way to check the preventive effect of double gloving is to use glove perforations as a proxy measure for needle stick injury. The number of glove perforations in the inner glove of the double gloves compared to the number of perforations in the single gloves gives a good indication of the preventive effect. Perforations can be measured in an objective way by means of a water or an air test. In studies that reported glove perforations, researchers collected all gloves that were worn during a procedure and used either a water leak test or an air leak test to count the number of perforations. During the tests, used gloves are filled with water or air and the perforations are visible when either water leaks from the glove or air bubbles rise when the gloves are hold under water. The preventive effect can also be measured by the number of needle stick injuries reported but the reporting is subjective and seems therefore less reliable. Also bloodstains can be used as an outcome measure but also here the measurement is rather subjective. In our systematic review we included randomised controlled studies that reported one, two or all of the outcomes.
Another benefit of using glove perforations to measure the effect is that they can be used to measure loss of dexterity. Loss of dexterity could result in more glove perforations instead of less. This can be measured by comparing the number of perforations in the outer glove of the double pair to the number in the single glove.
What did we include in the review?
For the review, we performed a systematic search for randomised controlled trials (RCT) in ten databases (CENTRAL, MEDLINE, EMBASE, NHSEED, Science Citation Index Expanded, CINAHL, NIOSHTIC, CISDOC, PsycINFO and LILACS) up until 26 June 2013. We included randomised controlled studies with healthcare workers, extra gloves or special types of gloves, and with exposure to blood or bodily fluids as the outcome.
We extracted the data of each study that fulfilled the inclusion criteria and performed a meta-analysis combining the results of the single studies within homogenous comparisons. Where needed, we recalculated perforations to the measure of the number sustained by one person during one operation. By doing so, the result presents the risk of a needle stick injury for one person during one operation.
What are the main results?
The review located 34 RCTs and 18 compared double to single gloves. The other 16 RCTs evaluated the effect of different glove materials and thicknesses, gloving methods (like triple gloving) and gloves with a colour indicator system. The gloves with an indicator system show a coloured spot when the outer glove gets perforated, thus making perforations more visible. In all but one study, the outcome was measured as the number of perforations in gloves, followed by the number of bloodstains on the skin in seven studies, and two studies used self-reported needle stick injuries. All studies were performed in the operating theatre with surgeons and 27 studies also included other surgical staff such as nurses. In total, the studies included 6890 operations. In the studies, the median perforation rate in the single gloved control group was 18.5 perforations per 100 operations for one person.
The methodological quality of the included RCTs was not optimal. Overall, the studies did not report their methods very clearly so we rated the quality of the evidence as moderate. We tried to retrieve the missing information but many studies were over 15 years old and so it was impossible to get clarification from the authors. We also wanted the studies to use both a water and an air test to assess perforations. We had less confidence in the results and we reduced the quality level of the evidence because this was not always done.
Twelve of the 18 studies that compared double to single gloves reported sufficient information on the number of persons per operation and could be included in the meta-analysis (Figure 1). Studies were performed between 1990 and 2004. The result of the meta-analysis shows that the risk of exposure is 71% lower when the worker wears two pairs of gloves compared to single gloves (rate ratio (RR) 0.29; 95% confidence interval (CI) 0.23–0.37).
This means double gloving protects the worker against 71% of all possible glove barrier failures compared to wearing only one pair of glove. A similar result was shown for the reduction of actual bloodstains on the skin. The meta-analysis showed a 65% reduction of the risk of bloodstains when wearing double gloves compared to single gloves (RR 0.35, 95% CI 0.17–0.70). Actual needle stick injuries were only reported in two studies and the effect was less clear. Studies showed a risk reduction with double gloves, but the result was statistical non-significant (RR 0.58, 95% CI 0.21–1.62).
The number of glove perforations is an objective measure of the potential exposure to blood but it is not the same as an actual needle stick injury. Gloves can already be perforated before use. The European standards specify that for surgical gloves perforations are allowed in 1.5% of new gloves (CEN 2003). However, for the effect of double gloving this does not matter because perforations in new gloves will be as likely in single as in double gloves.
Dexterity with the use of double gloves was measured in 13 studies by means of outer glove perforations and in four studies with self-reported dexterity on a visual analogue scale. With the visual analogue scale the glove wearer judges their experience after the procedure. The scale gives a rating, for example from 1 to 10, and a translation into common terms, for example 1–2=very poor, 3–4=poor, 5–6=average, 7–8=good, 9–10=very good.
We could combine eight of 13 studies reporting outer glove perforations in a meta-analysis. Those studies showed no statistical significant result (RR 1.10; 95% CI 0.93–1.31). This means that even so the number of outer glove perforations with double gloves could be 10% higher than with single gloves there is no definite answer if double gloving reduces dexterity. It is possible that the number of perforations is actually less with double gloves compared to single gloves.
Studies reporting VAS scores used different scales and domains so that a meta-analysis was not possible. The scores for dexterity for double gloves were in general a little lower than for single gloves. Three of four studies reported dexterity with double gloves as “good” in the domains of instrument handling, needle loading, knot tying, and tissue handling compared to “very good” with single gloves. Comfort and hand sensitivity was “good” when wearing one normal sized and one bigger sized glove but “fair” when wearing two normal sized gloves compared to “very good” scores with single gloves. One study reported “poor” or even “average” scores for double gloves in comparison to “good” with single gloves for the domains comfort and sensitivity.
It needs to be mentioned, that measuring the number of outer glove perforations is only a proxy measure for dexterity. It tells us something about the performance of the glove wearer and the results do not show a clear difference between single and double gloving in breaking the first protective barrier. The VAS scores provide us with information on how dexterity was experienced, but do not tell much about the practical relevance of the lower scores. It is further not known if more frequent use, training, or better fitting gloves could decrease the difference in experienced dexterity between double gloves and single gloves.
Using two pairs of gloves instead of one pair considerably decreases the risk of exposure to blood or bodily fluids for surgeons and surgical staff. Given the relatively large effect size and the consistency of the evidence, we believe there is no need for better studies among surgical staff. Other health care occupations will usually have a smaller risk of needle stick injuries. For them, a decision to use double gloves has to take into account if the absolute risk reduction outweighs the extra costs and drawbacks such as the potential loss of dexterity.
We like to acknowledge the work of our co-authors in the full Cochrane Review. The full review can be found in the Cochrane Library at www.thecochranelibrary.com.