Ryan Buchanan is a specialist registrar doctor in liver disease and a PhD student supported by CLAHRC Wessex.
In my previous blog I described how a novel, award winning case-finding initiative was identifying some of the estimated 200 missing cases of Hepatitis C on the Isle of Wight and linking them directly to specialist care. The second part of this project, which I describe here, is an attempt to establish a more accurate estimation of the true number of missing cases in order to guide future service design and inform best practice elsewhere.
The main risk factor for Hepatitis C is injecting drug use and therefore we focused our survey on people who inject, or have ever injected drugs on the Isle of Wight. This as you can imagine is a difficult group to survey with people unwilling to come forward due to issues surrounding privacy, stigma and the illegal nature of drug use.
Other researchers have addressed these challenges by undertaking surveys in locations where people who have injected drugs frequent regularly and feel able to participate – for example, drug support or needle exchange centres. However, we chose not to do this because survey designs such as this only sample people who going to support services and are therefore likely to have different characteristics to those who are not. The results of such a survey would therefore not be a true representation of the whole local population of people who inject drugs.
We have used a survey method called respondent driven sampling. In this method survey participants are asked to invite two or three of their friends and associates, who might also be at risk of Hepatitis C, to come forward to the research team. In this way we are potentially reaching more of a cross-section of people who inject drugs and can therefore make a better judgment about how common Hepatitis C is in this population as a whole.
Diagram showing how respondent driven sampling works, participant 1 (green) is asked by the research team to invite friends and contacts to take part (blue), if these attend then that are also asked to invite friends to take part (orange). The survey continues in this way until a sufficient number of people have taken part to give meaningful results.
Respondent driven sampling has been used successfully before in people who have or are currently injecting drugs, usually as part of research looking at HIV. However, it has only been used in rural communities a handful of times and this brings unique challenges.
Our survey has now started, we began with a carefully selected sample of participants who were able and enthusiastic to take part in the research and thought they had friends who were also willing to do so. These initial participants have gone on to invite these friends to take part and these have gone on to invite others and so it has continued. We have faced challenges during the process particularly posed by the rural nature of the Island community where people who are eligible to take part often live a long way from their friends and the survey centre.
It is hoped that on completion of the survey we will have a better idea about how many cases of Hepatitis C are actually missing on the Isle of Wight and importantly the characteristics of those that are missing. This will allow us to tailor our case-finding initiative for Hepatitis C so that it is accessible to the people that really need it.