A Need for Standardized Testing on Gloves
Testing for viral penetration of non-latex surgical and examination gloves
In response to a growing need to protect health care workers and patients from the possibility of transmission of HIV through contact with body fluids, the Centers for Disease Control and Prevention issued Universal Precaution Standards. Consequently, the use of examination gloves in clinical practice rose dramatically.
To ensure consistent quality of glove manufacture, the Food and Drug Administration introduced a two-part testing protocol in which gloves are first inspected visually and then subjected to a water-leak test, performed according to a national standard.
These tests, while inexpensive, suffer from a number of drawbacks. Both tests require the constant attention of a trained operator, and are therefore subject to variable results between operators. It has also been observed that microorganisms can penetrate gloves that do not show visible water leaks.
Studies that use microorganisms to gauge the propensity of gloves to permit penetration by pathogens examine the question more directly than water-leak studies. However, currently, there are no widely accepted or adopted standards for the use of microorganisms in assaying the barrier quality of examination or surgical gloves.
The American Society for Testing and Materials has established viral testing standards for determining the barrier quality of clothing materials. This method can be used to test samples of materials from which gloves are made.
However, it is not suitable, as written, for testing whole, intact gloves, and currently there is no established national standard for the testing of medical examination or surgical gloves that directly addresses the question: does the glove provide a barrier against viral passage between the patient and the wearer?
In our study, three methods for testing gloves for viral penetration were compared: two methods in which liquid-filled gloves were agitated; and a third method in which a liquid-filled glove was simply draped over a container. In each case, liquid either inside or outside the glove was spiked with a bacteriophage suspension, while an unspiked liquid was placed on the other side of the glove barrier, and later sampled to determine whether viruses penetrated the barrier. A stress or use protocol was also incorporated, in which gloves were worn during manipulation of instruments and materials handled commonly by healthcare workers, as in previous work using the water leak test.
Introduction
Currently, there are no international standards based on microbiological methodology for testing the ability of medical examination or surgical gloves to prevent the passage of viruses. So we decided to create one.
Three protocols for the direct examination of the viral barrier properties of non-latex gloves were compared with 1080 gloves (270 gloves from each of two surgical brands and two medical examination brands). In two of the methods, gloves were filled with and suspended in a nutrient broth solution, and bacteriophage ?X174 was placed either inside or outside the glove, while the entire test vessel was agitated.
Gloves tested using the third method were filled with a suspension of bacteriophage and allowed to rest in a vessel containing nutrient broth. Gloves were tested directly from the manufacturer’s packaging, or after being punctured intentionally or subjected to a stress protocol. The passage of bacteriophage was detected with plaque assays.
Significant differences in failure rates between glove brands were apparent only among gloves that had been subjected to the stress protocol. Overall, the two methods in which bacteriophage were placed inside the gloves provided more sensitivity than the method in which bacteriophage was spiked into broth outside the gloves.
Thus the placement of bacteriophage inside test gloves (or the use of pressure across the glove barrier during testing), and the use of a standardised stress protocol, will improve significantly the ability of a glove test protocol to determine the relative quality of the barrier offered by medical examination and surgical gloves. Further research is needed to provide test methods that can incorporate reproducibly both the use of bacteriophage and simulated glove use in an industrial quality control setting.
Tests for viral penetration of gloves
Previously, several brands of examination and surgical gloves were tested using an automated water-testing machine, in accordance with an industry standard water-leak test. After 30 min, samples were drawn from inside and outside the glove and titered.
The best- and worst-performing examination and surgical glove brands were selected for testing by bacteriophage penetration assays in this study.
Stress protocols
One-third of the gloves from each brand were tested directly from the manufacturer’s packaging. Another third were intentionally punctured twice in each glove fingertip with an 18-gauge needle, as positive controls. The remaining gloves were donned and subjected to stress by manipulating items, as described previously.
Statistical methods
Data were analysed using the SPSS statistical software package was used to test the significance of differences between the frequency of viral penetration detected by each testing method and among glove brands.
Results
Differences in the effectiveness of glove testing methods
After removal from packaging and being intentionally punctured, subjected to a stress protocol, or left untouched, gloves were tested by one of three methods for their ability to prevent viral penetration. Glove tests were scored as pass or fail, based upon whether bacteriophage penetrated each glove.
The effectiveness of detecting penetration of gloves by bacteriophage was significantly different among the three testing methods. Pairwise comparisons of viral penetration detected by the three methods across all glove brands and stress levels showed that method 1 detected viral penetration significantly less often than either method 2 or method 3. There was no significant difference between the frequency of viral penetration observed by methods 2 and 3.
The differences observed between the three methods were found to be significant only when gloves were either stressed or punctured. The three methods were indistinguishable when gloves were tested directly out of the package, presumably because few gloves, if any, came from the manufacturers with defects. Methods 2 and 3 detected viral penetration more frequently in stressed gloves, or punctured gloves than method 1.
Bacteriophage penetration was detected in all the punctured examination gloves tested by methods 2 and 3, but in only 31 out of 60 examination gloves tested by method 1. Methods 2 and 3 also detected penetration in more punctured surgical gloves than did method 1.
Detection of differences between glove types and brands
When gloves were subjected to a stress protocol, gloves of Brand C allowed viral penetration least often (36/270; 13.3%), while Brand B allowed viral penetration most often (97/270; 39.5%). Overall, there were significant differences between the examination and surgical gloves tested, but the brand differences observed were more pronounced when the testing method was taken into account.
Significantly, differences among glove brands and types were most apparent after either stressing or puncturing the gloves. Not surprisingly, bacteriophages were observed to penetrate intentionally punctured gloves more frequently than gloves tested directly from packaging, or subjected to the stress protocol.
Discussion
Taken together, these results suggest that placing bacteriophage inside the gloves, whether suspended within a flask and agitated, or draped over the side of a beaker, provides a more sensitive means of detecting the passage of bacteriophage through a glove. This conclusion was illustrated most dramatically by the results of testing intentionally punctured gloves.
Bacteriophage penetration was detected in all 120 punctured examination gloves tested by methods 2 and 3, but with only 31 of 60 examination gloves tested by method 1. Similar results were obtained when testing surgical gloves. Although not measured in this study, this was probably caused by a slight elevation in the hydrostatic pressure inside gloves associated with agitation (method 2) or the pull of gravity (method 3), creating a net efflux of phage-laden buffer or medium through holes in the gloves.
These and other studies demonstrated that differences in barrier quality between glove types and materials are often accentuated by the application of stress, simulated use, or actual clinical use before testing in the experimental protocol. In the present study, differences in glove quality after simulated use differentiated between glove brands more effectively than simply testing gloves for leaks directly out of the manufacturer’s packaging.
The necessity of including some form of stress in any future standards seems evident; it can be assumed that holes are created during use of medical examination or surgical gloves, and any method that is used to test the quality of gloves as barriers to penetration by pathogens should include some test of durability. In addition, holes formed in snug-fitting gloves are enlarged by use and the tension of wearing them.
As the present study suggests, there is a need to include some differential in pressure across the glove material to simulate this tension. In the case of examination gloves, merely putting the challenge suspension inside the gloves was sufficient. For future testing of surgical gloves, it may be necessary to devise a means of creating more pressure, so that all positive control (i.e., intentionally punctured) gloves allow the passage of detectable amounts of bacteriophage.
The water-leak test used currently has the advantage of being simple and relatively inexpensive to perform. Machines have been built to facilitate water-leak testing by automating the filling of gloves and slowly conveying filled gloves past an inspector. While glove-testing using microorganisms is superior to water-leak testing in its sensitivity and relevance to worker and patient safety, all the methods have the drawback of requiring a microbiological laboratory and trained personnel to perform the testing.
Given the enormous volume of gloves made, worn, and disposed of world-wide, the microbiological testing of even 0.1% of each lot manufactured by any of the methods described in this study would present a significant cost increase for a glove manufacturer. If microbiological testing of gloves became mandatory, modern laboratory robotics might be used to partly automate the process.
A method for detecting bacteriophage from glove tests by PCR has been reported, and the use of real-time fluorogenic PCR would speed the microbial detection process greatly. Automated sample pipetting, PCR mixing, plate loading, and PCR product detection are all technologies available in the marketplace that could be adapted to the high-throughput screening of gloves in the industrial or regulatory quality assurance and control settings.
The combination of standardised methods for glove stressing with microbiological barrier testing would increase greatly the confidence of the medical community in one of the most critical components of personal protection, and ultimately provide consumers with meaningful data to compare glove quality as influenced by materials and manufacturers.
Denise M. Korniewicz, DNSc, RN, FAAN, is a Professor & Senior Associate Dean for Research, and Interim Assistant Dean of Student Services, Univertity of Miami.
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