Does geographic access to primary healthcare influence the detection of hepatitis C?

Recent work in France has suggested that poor geographic access to primary healthcare may have a negative influence upon detection rates of the hepatitis C virus. Topography and poor infrastructure can exacerbate geographic remoteness, while the stigma surrounding hepatitis C and intravenous drug use may also discourage healthcare-seeking behaviour in rural communities with limited choice of general practitioner. No similar study has been conducted in the UK, where detection rates of hepatitis C are also low. Moreover, the previous French findings did not adjust for the uneven spatial distribution of HCV prevalence and associated risk factors, which raises the possibility that the reported travel-time associations were a reflection of greater hepatitis C prevalence in urban areas (where the travel-times to primary healthcare are short) and not an effect of geographic access to primary healthcare. Using geographic information systems, Poisson regression and a dataset from Tayside (Scotland), we explored whether lower rates of hepatitis C detection were associated with higher travel-times to primary healthcare. We tested whether any travel-time effects remained once the models were adjusted for deprivation, by controlling for the spatial variation of some of the known risk factors of hepatitis C infection. Separate models were calculated according to patient history of opiate substitution therapy to take account of people likely to have been infected through intravenous drug use. Rates of detected hepatitis C were highest among males aged between 25 and 39 years. A statistically significant travel-time-decay effect was observed, though with notable attenuation for all patients after adjusting for deprivation. Further modelling identified a travel-time effect only for those who had received opiate substitution therapy. The absence of a similar effect in the non-opiate substitution therapy group indicates that selection effects, not causation, are the most likely explanation for the initial travel-time-decay effects. Thus, future studies of hepatitis C detection and geographic access to primary healthcare will need to consider ways of controlling for the uneven spatial distribution of HCV prevalence and associated risk factors beyond ecological measures of socioeconomic deprivation.