Vitamin D levels did not show any significant association with the outcome of antiviral therapy among a cohort infected with hepatitis C virus genotype 1, according to new study findings.
“Our results reveal substantial fluctuations of [25-hydroxyvitamin D3] levels during antiviral therapy. … Yet, no association to treatment outcome was identifiable,” researchers wrote in PLoS One.
The study included a well-characterized cohort of 398 patients with HCV genotype 1 infection who were treated with pegylated interferon alpha (PEG-IFNa) and ribavirin for 24 to 72 weeks. The researchers analyzed the predictive potential of 25-hydroxyvitamin, or 25-(OH)D, levels before and during treatment, since previous studies have only included analysis of baseline concentrations of vitamin D. In addition, the researchers analyzed the role in treatment outcome of single nucleotide polymorphisms (SNPs) known to regulate vitamin D metabolism. Other known treatment predictors, such as age and cholesterol levels, also were evaluated.
Results indicated a vitamin D deficiency (<20 ng/mL) among the cohort, with mean concentrations before and during therapy of 18.7 ng/mL and 19.5 ng/mL, respectively. The researchers observed fluctuations in 25-(OH)D levels of more than 10 ng/mL in nearly 40% of the cohort during the course of antiviral therapy. Despite these fluctuations, 25-(OH)D levels before and during treatment were not associated with sustained virologic response (SVR).
Initial analysis showed that the DHCR7-TT SNP was associated with SVR rates (P=.031), but this association was attenuated after controlling for other predictive factors.
Additional characteristics, including age (OR=1.028; 95% CI, 1.002-1.056), cholesterol (OR=0.983; 95% CI, 0.975-0.991), ferritin (OR=1.002; 95% CI, 1-1.004), gamma-glutamyltransferase (OR=1.467; 95% CI, 1.073-2.006) and the IL28B genotype (OR=2.442; 95% CI, 1.271-4.695) were all strongly associated with treatment outcome.
Although vitamin D levels failed to predict treatment outcome with PEG-IFNa and ribavirin, continued analysis of genetic data may hold the key to understanding the role of vitamin D metabolism in treatment success, the researchers said.
“Fluctuations in [vitamin D] levels during antiviral therapy may be due to environmental factors rather than to virus- or antiviral therapy-related effects, whereas the evaluation of SNPs within [vitamin D] regulating enzymes constitutes an important component in further deciphering the role of [vitamin D] metabolism in chronic HCV infection,” they wrote.
Disclosure: The researchers report no relevant financial disclosures.