- Created on Thursday, 07 May 2009 13:15
Medical surgeon and examination gloves need to be able to exhibit a minimum strength, possess barrier protection against microorganisms during use and fit the user correctly. They should also be safe for the user to wear and have a reasonable shelf life.
It is becoming common practise for procurement bodies to request independent test reports stating compliance with EN 455 from ISO 17025 accredited laboratories. Independent testing can demonstrate that medical gloves meet the appropriate performance requirements.
The SMTL works closely with glove suppliers and manufacturers, providing reliable compliance testing to the EN 455 series of standards for nitrile, latex and vinyl examination and surgical gloves as follows:
- BS EN 455-1 - Medical gloves for single use: Requirements and testing for freedom from holes
- BS EN 455-2 - Medical gloves for single use: Requirements and testing for physical properties
- BS EN 455-3 - Medical gloves for single use: Requirements and testing for biological evaluation
- BS EN 455-4 - Medical gloves for single use. Requirements and testing for shelf life determination
In detail - what do these standards cover ?
The standards describe a number of tests applicable to examination and surgical gloves used in healthcare.
BS EN 455-1
This standard describes a method in which randomly sampled gloves are subjected to a watertightness test (ability to hold 1000ml of water without leaking). The number of gloves to be tested are based on the batch size of the gloves manufactured as stated in the International Standard ISO 2859-1 i.e. if the laboratory is using a multiple sampling plan then the following gloves will be required for testing:-
- Batch size 0 - 150,000 gloves = 300 gloves supplied for testing
- Batch size 150,001 - 500,000 gloves = 450 gloves supplied for testing
- Batch size 500,001+ gloves = 650 gloves supplied for testing
For compliance to the BS EN 455-1, the accepted quality level shall be 1.5%.
This standard describes the testing requirements for determination of physical properties, including break strength, before and after accelerated ageing, of medical gloves for single use, surgical gloves, examination/procedure gloves, long-cuff medical gloves, and seemed/welded gloves.
Note that the recent amendment to the standard, BS EN 455-2:2009+A1:2011, has reduced the FAB (force at break requirement) for examination gloves from 9N to 6N, and for surgical gloves from 12N to 9N. The UK forward to this version of the standard states:
"This does not prevent Purchasers who wish to do so continuing to specify higher values in contract negotiations."
BS EN 455-3
This standard covers protein testing (extractable latex proteins have an important role in latex allergy), powder levels, and endotoxin levels.
BS EN 455-4
This standard covers real-time and accelerated shelf life studies, to enable manufacturers to prove that their product will withstand up to 3 years (usually) without losing their strength and barrier properties.
Other standards and tests ...
SMTL also offer a number of other currently non-accredited test methods such as Chemical Permeation testing and Bacterial & Viral barrier testing
BS EN 374-3:2003 Protective gloves against chemicals and micro-organisms: Determination of resistance to permeation by chemicals
This European Standard specifies the determination of the resistance of protective glove materials to permeation by potentially hazardous non-gaseous chemicals under the condition of continuous contact. A simple flow-through, two compartment permeation cell, of standard dimensions, is used to measure quantitatively the permeation of chemicals through protective glove materials. Breakthrough time is measured and used as a measure of protection.
BS EN ISO 21171 2006 Medical gloves. Determination of removable surface powder
Depending on their method of manufacture, some medical gloves can have on their surface a small amount of powder, normally modified corn-starch, which is intended to assist donning. Current thinking is that the presence of excessive amounts of such powder can present a health hazard. In this method the mass of removable surface powder is calculated, and for compliance the recovered mass per glove should be below 2mg (i.e. the limit is taken from BS EN 455-3:2006).
Bacterial & Viral Barrier Testing
The SMTL have developed a test to assess the bacterial and viral barrier properties of gloves. This method is in the final stages of validation and we should be in a position to offer this commercially shortly.
What does the modified Lowry protein test detect ?
The modified Lowry protein assay detects levels of water soluble proteins in the gloves under test.
An assumption is made with this test that the level of protein detected correlates with the likelihood of the glove producing an immediate (Type I) hypersensitivity reaction in a user or patient.
This test method is currently used as the soluble protein assay for European standard EN-455 Part 3.
There are certain problems with the test:
- It is non-specific - it detects all proteins, not just allergens.
- It is susceptible to interfering substances, such as surfactants and accelerators present in the latex.
SMTL are UKAS accredited for this test.
Why does SMTL recommend testing 4 gloves from each batch?
In the manufacture of surgical and examination glove lots, it is normal to process the left-hand and right-hand gloves separately and then pair these up at a final air-test and visual examination stage that immediately precedes placing the gloves in the final pack.
Thus, the actual hour of manufacture may differ by 12 hours or more between left and right-hand gloves in a lot. In addition, manufacturing conditions can vary throughout a batch, and thus the results from a single sample will not necessarily reflect the level of protein throughout a batch.
SMTL (in association with an independent rubber consultant) therefore suggest that, for initial assessment of gloves from any company for measurement of protein, two left and two-right hand gloves should be taken from a single nominal lot (4 samples for Examination gloves).
Whilst these sample sizes are not statistically significant, SMTL believe it is a pragmatic compromise between the cost of testing and useful test data.
SMTL will, of course, carry out single sample testing if required, with a consequent reduction in testing costs.