Among a large, ethnically diverse population of adults with chronic hepatitis C virus (HCV) infection, African Americans were 57% less likely than whites to be cured, despite optimal therapy, researchers reported in a study published in Pharmacology Research & Perspectives.
Adherence to medication regimens appears to play a role, but the researchers also noted that, “These data suggest potential underlying biological differences between white people and African Americans in medication response.”
In previous studies, other researchers have also found that African Americans have lower HCV cure rates than whites, as demonstrated by lower sustained virological response (SVR). But what isn’t known is whether such race-based differences in SVR are due to genetic, socioeconomic, and/or other factors.
Lower odds for a cure
For this observational study, researchers conducted a retrospective analysis of 1,068 patients who received HCV treatment at the Veterans Administration (VA) Greater Los Angeles Healthcare System between 2014 and 2016. Men comprised 97% of the study cohort, and the mean age of participants was 61.8 years. Whites and African Americans each accounted for a 37.8% share of the population. The most common HCV genotype was genotype 1 (83.9%), followed by genotype 2 (7.9%). No patient had genotype 5.
All patients were treated with direct-acting antivirals (DAAs), and the most common regimen was sofosbuvir/ledipasvir with or without ribavirin (47.8%). Older antiviral regimens included sofosbuvir/simeprevir, sofosbuvir/simeprevir with or without ribavirin, and sofosbuvir/ribavirin.
After 12 weeks of treatment, 87% of all patients attained SVR.
But when researchers adjusted for various factors—including age, HCV genotype, DAA regimen and duration, human immunodeficiency virus status, fibrosis, nonalcoholic fatty liver disease fibrosis score, homelessness, mental health, and adherence—they found that African Americans had 57% lower odds for achieving SVR at 12 weeks (SVR12) compared with whites (adjusted odds ratio [aOR]: 0.43, 95% confidence interval [CI]: 1.5-4.1).
The researchers also found that subjects with advanced fibrosis had 60% lower odds for being cured (aOR: 0.40, 95% CI: 0.26-0.68). The reasons for these differences are unclear, they noted, but added that medication adherence and biological causes are likely factors.
• Adherence – “We find that patients with adherence rates of < 90% did not reach SVR12. Adherence appeared to attenuate the association between race/ethnicity and SVR12, thus explaining some of the differences observed,” wrote researchers, led by Joseph Pisegna, MD, chief, Division of Gastroenterology, Hepatology and Parenteral Nutrition, VA Greater Los Angeles Healthcare System, Los Angeles, CA.
• Biological causes – “One potential biological explanation for these observations is differences in drug metabolism, driven by the patients’ genetic background,” according to Dr. Pisegna and colleagues. “Drug metabolism differences have been described to exist between African-Americans and white people.”
Another possible reason for cure disparities: HCV genotypes may have different effects on each race/ethnicity, they speculated.
“Although we did not stratify our data by genotype for each race, it is possible that some of the differences observed were driven by the virus genotype. For example, the aOR for genotype 2 dramatically improved (0.5-2.5) after adjusting for other covariates,” the researchers noted.
“Although our data demonstrate the importance of racial/ethnic differences, the true etiology of these differences remains unclear, which can be further explored in prospective studies where drug levels and patient genetics are taken into account,” Dr. Pisegna and coauthors concluded.