Articles addressing the transmission of HCV through tattooing and piercing were identified through a literature search using PubMed and Medline. The search was limited to articles published from 1994 through July 2011 in all languages. A combination of the Medical Subject Headings terms “hepatitis C,” “HCV,” “tattooing,” “tattoo,” and “piercing” was used to identify potentially relevant abstracts and articles. Relevant references cited in identified studies were also assessed for inclusion. Articles published in languages other than English and French were evaluated on the basis of information included in the English abstract only. Unpublished, non-peer-reviewed studies were not retrieved because of the questionable reliability of such reports. The first author (R. T.) performed the search and retrieved the articles. Both authors (R. T. and S. H.) evaluated the validity of inclusion of each article and agreed on the strength of evidence in each based on preset ratings (Table 1).

The literature search resulted in the retrieval of 293 published articles or abstracts on HCV infection that included information about tattooing and/or piercing exposure. However, 231 studies were excluded because they were review papers (n = 47), did not measure the risk of HCV infection through tattooing or piercing (ie, relied on descriptive statistics and did not include measures of association, such as odds ratios (ORs) and relative risk; n = 163), did not control for any HCV infection risk factor (eg, drug use, transfusion before 1992, hemodialysis, contact with blood from HCV-infected person, and number of sex partners) when assessing the risk (n = 14), were duplicate studies (n = 4), were editorials or author responses (n = 2), or relied on self-reported HCV infection (n = 1). Therefore, a total of 62 articles were eligible for inclusion.

We used the Meta-analysis of Observational Studies in Epidemiology and the Grades of Recommendation, Assessment, Development, and Evaluation guidelines to evaluate the quality of evidence [8, 9]. Table 1 summarizes the criteria used to evaluate and rate the strength of the evidence in each study. Final rating consisted of adding the rates in each category. Reports were evaluated on the basis of the study design, representativeness of the study population, adjustment for other HCV infection risk factors, and use of adequate laboratory testing methods for ascertainment of HCV infection. Cohort and case-control studies were given the highest rates, followed by cross-sectional studies. Case reports or case series were rated lowest, because the sample size from these types of studies is typically insufficient to quantify risk of HCV transmission. Studies that included incident cases of HCV infection; a sample size including at least 100 cases for case-control studies and 2000 individuals for cross-sectional studies (calculated considering a power of 80%, an α of 0.05, and an estimated OR of 2 and taking into account the variability in HCV infection and tattoo prevalence rates in different study populations); controlled for other hepatitis C risk factors, including mainly IDU and transfusion of blood or blood products; and confirmed HCV infection with recombinant immunoblot assay or nucleic acid testing were given additional rating.

The magnitudes of the risk of HCV transmission through tattooing and piercing were presented as adjusted ORs (AORs) obtained by compiling AORs from studies that controlled for the most common routes of HCV transmission, particularly IDU. Because of the wide variability in the characteristics of study populations, we separately evaluated the risk of HCV infection from tattooing in the general population, blood donors, high-risk groups (ie, drug users, homeless persons, sex workers, and patients in sexually transmitted disease clinics), prisoners, and veterans. High-risk groups, prisoners, and veterans have been shown to have higher prevalence rates of IDU and HCV infection than the general population [1, 10–12], which could jeopardize analyses and conclusions if they are aggregated with low-risk groups. In addition, when information was available in the study, we separately assessed the risk of transmission of HCV infection from tattooing and piercing performed in professional parlors (ie, commercial venues that are licensed and regulated by health authorities), compared with those performed in nonprofessional settings under potentially nonsterile conditions (eg, by friends, at home, or in prison).

Table 2 summarizes findings from studies in the general population. Of 10 case-control studies, 6 reported no increased risk of HCV infection from tattooing when they controlled for IDU and other risk behaviors [15, 16, 18, 20–22], and 2 studies reported a 2–3 times higher risk for HCV infection when the tattoo was received in nonprofessional settings [14, 17]. One hospital-based case-control study including 64 patients and 128 control subjects did not find a significant association between tattooing and HCV infection in univariate analysis and, thus, excluded tattooing from the multivariate model [32]. Of the few reports showing an association between tattooing and HCV infection, 1 study compared 598 patients with acute HCV infection with 7221 control subjects with acute hepatitis A virus infection [13]. Patients with acute hepatitis A virus infection were younger and lived in other geographic areas, compared with those with acute HCV infection, which might affect the validity of the findings. Another study recruited 58 patients and 58 control subjects from a gastroenterology clinic, which limited generalizability of its findings [19]. More important, 29% of the originally enrolled study population admitted IDU when requestioned, and control subjects were not tested to confirm that they were not HCV infected. Moreover, tattooing was frequently performed by family members or friends using unhygienic techniques [19].

A cross-sectional study including >5000 college students in the United States revealed no risk of HCV infection when the tattoo was performed in a professional setting (AOR, 0.8; 95% confidence interval [CI], 0.4–1.7), whereas the risk was significant for tattoos performed in nonprofessional settings (AOR, 3.5; 95% CI, 1.4–8.8) [23]. Other large cross-sectional studies indicated an association between tattooing and HCV infection but did not specify venue of tattooing [25, 26, 29]. A cross-sectional hospital-based survey in Brazil showed an increased risk of HCV infection among persons having a tattoo; however, more than half of individuals received their tattoos in nonprofessional settings using nonsterile instruments [27]. Moreover, 26% of those who had a tattoo reported IDU, compared with 0% of those who did not have a tattoo [33].

Only one early (1991–1992) cross-sectional study conducted among a selected US population (minority, indigent, and orthopedic patients) indicated a potential risk of HCV transmission by tattooing in commercial parlors [24]. One case report suggested potential hepatitis C transmission by tattooing in commercial parlors from reuse of nondisposable tattooing needles that are not appropriately sterilized [34].

Persons with certain high-risk behaviors are excluded from blood donation, and several countries require persons who have recently had a tattoo or body piercing to defer from blood donation for at least 6 months, leading to lower rates of risk behaviors in this population. All studies conducted among blood donors did not inquire about the venue of tattooing. As shown in Table 3, almost all studies of these low-risk individuals that controlled for major HCV infection risk factors have not reported an increased risk for HCV infection from tattooing [37–39, 42–44, 47]. Case-control studies conducted in large samples of blood donors in the United States did not show an increased risk of HCV transmission from tattooing, but did report significant associations between tattooing and IDU [43, 44].

Some studies suggest that tattoos received before 1995 increased the risk of HCV infection, whereas those received after 2005 did not [35, 36, 40, 41, 45, 46]. However, none of the studies recruited patients with incident cases, limiting the ability to draw temporal causality. One study involving blood donors in Canada found that the odds of HCV infection from tattooing were much lower among blood donors in 2005 (AOR, 2.9; 95% CI, 1.2–7.0) than among blood donors in 1993 (AOR, 8.3; 95% CI, 2.8–24.5) [32]. However, the venue of tattooing was not specified.

Table 4 summarizes the findings of studies that assessed the risk of HCV infection from tattooing in high-risk groups. Two cohort studies conducted among prisoners in Australia reported discrepant findings. The study that recruited a larger sample (n = 488) showed a significant association between tattooing and HCV infection [48]; the other study, which did not find such an association, recruited 181 prisoners, a smaller number, which might have limited the power to demonstrate statistical significance [49]. Although cohort studies followed up with prisoners over >4 years, the presence of tattooing was assessed during their lifetime and not necessarily during their time in prison; this hinders temporal linkage between tattooing and HCV infection [48, 49].

Results from cross-sectional studies involving incarcerated individuals have been inconsistent. Two studies conducted in the United States among incarcerated youths reported no increased risk of HCV infection among those who were tattooed, even if the tattoo was applied in a nonprofessional setting [56, 58]. However, several studies from other countries found a 2–3 times higher likelihood of HCV infection among prisoners who had a tattoo [51–55, 57]. Of note, approximately 90% of prisoners received tattoos in nonprofessional settings [57]. Case reports of acute HCV infection from tattooing in prison suggest that tattooing could be the source of infection [67–69]. One case report documented seroconversion in a prisoner after a negative hepatitis C test result, and tattooing in prison was the only risk factor during the incubation period [67].

Findings from cross-sectional studies involving injection drug users varied by country, duration of injection, and incarceration [59–61]. Although the risk of HCV infection increased by 3 times among injection drug users who had tattoos applied in prison or jail, the risk was not statistically significant if the tattoos were received outside prison or jail [61]. Current noninjecting heroin users who reported never injecting drugs did not have a significantly increased risk of HCV infection from tattooing, whereas former injectors who had a tattoo had 3 times higher risk of HCV infection [63]. Other studies involving noninjection drug users reported a 2–3 times higher risk of HCV infection among those who had a tattoo [62, 64], and 1 study specified that the tattoos were applied by friends or relatives [64].

Studies involving street youths and homeless persons did not find an association between HCV infection and tattoos [65, 70], with 57% of homeless persons reporting IDU and 41% of them having shared needles with others [70].

Tattoos are highly prevalent among soldiers. Almost 36% of soldiers in the US Army had at least 1 tattoo, and 76% experienced bleeding after the procedure, which might promote transmission of blood-borne infections [71]. Studies that recruited >1000 veterans found almost 3 times higher risk of HCV infection among veterans with a tattoo, compared with those who did not have a tattoo (Table 4) [11, 12, 66]. However, in all studies, the researchers did not inquire about the venue of tattooing.

Table 5 summarizes findings of studies that assessed the risk of HCV infection among those who reported having a body or ear piercing. The majority of studies did not distinguish between piercings received in professional settings from those received in nonprofessional settings. Only 5 of 23 studies reported an increased risk of HCV infection among persons with a piercing (AOR, 2.0–7.3) [13, 22, 43, 44, 73]. Of the 5, 2 were conducted among blood donors in the United States during the early 1990s [43, 44], with 1 study showing a significant association between ear piercing and HCV infection only among men and no association among women [44].

Moreover, a number of cohort, case-control, and cross-sectional studies involving high-risk groups did not find significant associations between body piercing and HCV infection in univariate analysis and, thus, did not include this variable in the multivariable model [32, 48, 62, 64]. A cross-sectional study including >5000 college students in the United States did not reveal an increased risk of HCV infection among those with a body piercing [23]. Acute HCV infection occurred after ear piercing with a gun at a jeweler in an older French woman with no other identified risk factor [74]. Swapping body piercing jewelry was also reported as a potential source of HCV infection in another case report [75].