Can reducing the ‘dead space’ in injecting equipment save lives, asks Jamie Bridge.
For the more than 100,000 people who inject drugs in the UK, needle and syringe programmes have proven invaluable since their official adoption by the mid-1980s Conservative government. These services have helped to avert an HIV epidemic among this population – with HIV rates now consistently below 2 per cent among current and former injectors nationwide – and a huge international body of evidence has been developed to demonstrate how these services can reduce not only risk behaviours and HIV transmission, but injecting frequency and returns of used equipment. They also enable referrals to drug treatment and save public money, hence their adoption in 86 countries around the world and their inclusion in the UK Drug strategy 2010.
The impact on viral hepatitis, however, has been much more modest – around half of all people who inject drugs in the UK may be infected with hepatitis C, with little change since 2001. This reflects the fact that the hepatitis C virus is more easily transmissible than HIV, and so requires even higher coverage levels for prevention services. According to the Health Protection Agency (HPA), 57 per cent of people who inject drugs in England receive enough needles to cover every injection, yet a quarter of current injectors aged under 25 still reported needle and syringe sharing.
Emerging evidence, however, suggests that the design of the needles and syringes themselves could help to further reduce HIV and hepatitis C transmission – depending on how much ‘dead space’ they contain.
Every syringe inevitably retains some fluid when its plunger is fully depressed, in what is known as the dead space. As the diagram shows, some types of syringe will contain more of this dead space than others. ‘High dead space’ syringes with detachable needles will retain fluid in the tip of the syringe, the hub of the needle and the needle shaft itself. In ‘low dead space’ designs with permanently attached needles – such as the 1ml insulin needles used by many people who inject drugs – fluid is only retained in the needle shaft.
The difference can be up to 40 times more fluid being retained in high dead space syringes compared to low dead space ones. In laboratory experiments that simulated common injection practices, low dead space syringes retained up to 1,000 times less blood than high dead space syringes, so if a person shares a low dead space syringe with someone living with HIV there will be less blood retained in the syringe and therefore less viral load and a lower risk of transmission.
Modelling work by Dr William Zule and colleagues in the USA has helped to quantify what this could mean in the real world. Their results suggest that injection-related HIV epidemics could be stabilised, reversed or avoided altogether when the majority of people who inject drugs use low dead space syringes. Laboratory studies have also shown that the hepatitis C virus can survive for up to 60 days in high dead space syringes, compared to just one day in low dead space alternatives – hence the inclusion of low dead space syringes in the latest World Health Organization guidance on viral hepatitis prevention among people who inject drugs.
More research is needed, particularly to assess how effective low dead space syringes can be in the real world, rather than in models and laboratories. But it is an area of great promise. Provided it is managed carefully, the transition from high dead space to low dead space syringes is also a risk-free intervention for services to provide as part of a comprehensive harm reduction package. It must never be a substitute for the highest possible coverage of harm reduction services, but rather a complementary string to the bow to make these programmes even more effective.
Crucially, a shift from high dead space to low dead space syringes should never be forced upon someone. People who inject drugs may prefer a wide range of different syringes and needles and this needs to be respected. In particular, 1ml insulin syringes with fixed needles – which often have the lowest dead space – may be unsuitable for the injection of certain drugs, or for injecting in certain parts of the body. It is essential that clients are widely consulted in order to ensure the appropriateness of any equipment supplied, and it’s important not to lose the emphasis on the potential harms of injecting and – particularly – sharing needles and syringes.
To facilitate this consultation, low dead space alternatives are now available in a range of sizes and with both fixed and detachable needles. Exchange Supplies have developed a range of ‘Total Dose’ low dead space needles and syringes which have a plastic ‘spike’ that fits inside the tip of the syringe while the syringes have a ‘spike’ on the end of the plunger. Importantly, these products are also available at prices similar to high dead space needles and syringes whereas traditionally low dead space alternatives have been perceived as being too expensive to justify.
Low dead space needles and syringes are a potentially crucial addition to the harm reduction armoury. Do you know what kinds of needle and syringe your local services are supplying?
Jamie Bridge is chair of the National Needle Exchange Forum (NNEF).
Low dead space needles and syringes will be among the topics discussed at the NNEF meeting on 20 September, free to attend for needle and syringe programme workers, users and advocates. See www.nnef.org.uk for details.