A pooled analysis of 25 studies has shown for the first time
good evidence that methadone and other forms of opioid substitution therapy
substantially reduce new hepatitis C infections. Previously, this had been
clearly demonstrated for HIV, but not hepatitis C.
While an independent effect of needle and syringe exchange
on hepatitis C was not demonstrated, programmes which combined opioid
substitution therapy with needle and syringe exchange were more effective. Lucy
Platt of the London School of Hygiene and Tropical Medicine presented the
results to the 24th International Harm Reduction Conference in Kuala
Lumpur, Malaysia, today.
In most settings, the proportion of people who inject drugs
who have hepatitis C is far higher than the proportion who have HIV.
Furthermore, the hepatitis C virus is readily transmissible in miniscule
quantities and for several weeks outside the body. The combination of these
factors make hepatitis C harder to keep under control than HIV.
Two previous systematic reviews on the topic did not
demonstrate that needle and syringe programmes (NSP) and opioid substitution
therapy (OST) were effective in preventing the spread of hepatitis C. However
the new systematic review and meta-analysis is able to take account of several
studies published in the past few years and also deal with some methodological problems
of previous reviews.
The data from all relevant studies which met
pre-determined
quality criteria were included. Of note, these were all observational
studies –
mostly prospective cohorts but also some cross-sectional and
case-control
studies. In total, 25 studies were included – mostly from the USA,
Canada, UK and Australia, plus a few from other European countries.
Opioid substitution therapy supplies users of an illegal
drug (such as heroin) with a replacement drug (such as methadone or buprenorphine)
under medical supervision. This helps the person reduce the frequency of
injections and reduce their dependence on illegal drugs.
The analysis compared rates of new hepatitis C infections in
people who currently (or had recently) received opioid substitution therapy with
infections in people who did not get OST.
There were 1089 new hepatitis C infections in the studies
with over 4,262 person years of follow up. Individuals receiving OST had a 39%
lower risk of acquiring hepatitis C (rate ratio 0.61, 95% confidence interval
0.46 – 0.80).
The results did not vary according to characteristics of the
study participants (such as experience of prison, homelessness or frequency of
injecting). On the other hand, studies with a lot of female participants showed
OST to be somewhat less effective.
In sensitivity analyses which excluded studies with a weaker
methodology or a greater risk of bias, the results showed OST to be even more
effective. Further, there was no evidence of publication bias (a tendency of
researchers only to publish encouraging findings).
Next, the researchers looked at new hepatitis C infections
in people who did (or did not) receive ‘high’ coverage of needle and syringe
programmes – in other words, having enough sterile equipment for every
injection or regularly attending a NSP. In studies assessing this, there were
641 new infections in 1015 person years of follow-up.
Here, the evidence was weaker and was not statistically
significant (rate ratio 0.83, 95% confidence interval 0.43 – 1.61). There was
considerable variation between studies, with European studies more likely to
show effectiveness.
But analysis of people who received both OST and high
coverage of NSP showed that hepatitis C infections were reduced by 71% and this
was statistically significant. (Rate ratio 0.29, 95% confidence interval 0.13 –
0.65). Results were consistent in sensitivity analyses.
“In summary, there is strong evidence that opiate
substitution therapy reduces HCV transmission,” concluded Lucy Platt.