Hepatitis C virus infection among people who inject drugs in Bangkok, Thailand, 2005–2010

ABSTRACT

Background Approximately 1% of adults in Thailand are infected with hepatitis C virus (HCV). Newdirect-acting antiviral agents achieve sustained virologic responses in >95% of HCV-infected patientsand are becoming available in countries around the world. To prepare for new HCV treatment optionsin Thailand, this study characterized HCV infections among people who inject drugs (PWID) inBangkok.Methods The Bangkok Tenofovir Study (BTS) was a pre-exposure prophylaxis trial conducted amongPWID, 2005–2013. Blood specimens were randomly selected from PWID screened for the BTS, to testfor anti-HCV antibody and HCV RNA. The HVR1 region was amplified by polymerase chain reaction,using multiplex primer sets with unique identifier sequences; amplification products were pooled in setsof 25; and consensus sequencing was performed to characterize individual HCV genotypes.Results The median age of 3679 participants tested for anti-HCV antibody was 31 years, 3016(82.0%) were male and 447 (12.2%) were HIV infected. The prevalence of anti-HCV antibody was44.3%. The adjusted odds of testing positive for anti-HCV antibody were higher in men (adjustedodds ratio [aOR] 3.2, 95% confidence interval [CI] 2.4–4.3), those aged 40 years or older (aOR 2.7,95% CI 2.1–3.5), those who had more than a primary school education (aOR 1.7, 95% CI 1.4–2.1),and those who tested HIV positive (aOR 5.2, 95% CI 3.7–7.4). HCV RNA was detected in 644(81.3%) of the 792 anti-HCV antibody-positive specimens, yielding an HCV RNA-positive prevalenceof 36.0% (95% CI 33.8–38.2). Among a random sample of 249 of the 644 specimens, 218 could becharacterized, and the most common HCV subtypes were 1a (30.3%), 1b (12.8%), 3a (35.8%), 3b(6.9%) and 6n (8.7%).Conclusion The prevalence of anti-HCV antibody among PWID was 44.3% and more than one third(36.0%) were HCV RNA positive. Genotypes 1, 3 and 6 accounted for all typable infections. As thegovernment of Thailand considers introduction of direct-acting antiviral medications for people withhepatitis C, it will be important to ensure that the medications target these subtypes.