Hepatitis C virus (HCV) infection is more common in people who have had a tattoo, research shows.
Significantly, this relationship held true in patients without other risk factors for infection, such as a history of blood transfusion or injection drug use.
"These findings have important implications for screening non-injection drug users in the United States, particularly since the prevalence of tattooing is on the rise and intravenous drug use is on the decline," say Fritz Francois (New York University, USA) and colleagues.
The study included 1930 patients with chronic HCV infection and 1941 HCV-negative controls.
Injection drug use (64.9 vs 17.8%) and blood transfusion prior to 1992 (22.3 vs 11.1%) were both significantly more common in HCV-positive patients than HCV-negative patients, as expected.
However, the authors also found that having had at least one tattoo was associated with a 3.7-fold increase in the odds of HCV infection, after adjusting for confounders, such as injection drug use, blood transfusion history, ethnicity, income, reported sex with prostitutes and body piercings.
When the authors excluded patients who had injection drug use history or had a blood transfusion before 1992, this rose to a 5.2-fold increase in the odds of infection, and an 8.2-fold increase when intranasal drug users were also excluded.
HCV could be transmitted during tattooing through the use of nondisposable needles, inadequate sterilization of equipment, or the reuse of ink contaminated with blood, explain the authors.
However, previous studies into the association between HCV-infection and tattooing have led to conflicting results, and have not always adequately controlled for additional risk factors.
"Our study confirms the association between tattoo exposure and hepatitis C infection in a very large ethnically diverse population of HCV cases and uninfected controls," write Francois and colleagues in Hepatology.
They say that their findings could lead to changes in HCV screening practices. "All patients who have tattoos should be considered at higher risk for HCV infection and should be offered HCV counseling and testing."
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