Highlights
In this single-center cohort of 146 HBsAg-positive, anti-HDV-positive patients, combined assessment of serum HDV RNA and anti-HDV titers provided clinically useful information across diagnosis, disease staging, and post-treatment follow-up.
Very low anti-HDV titers, particularly 1:100 or lower, clustered in patients without overt liver disease, especially when HDV RNA was undetectable or below 500 IU/mL.
Among patients with chronic hepatitis D, higher HDV RNA levels were associated with cirrhosis, higher alanine aminotransferase (ALT), and higher HBsAg levels, supporting the biological link between active HDV replication, hepatocellular injury, and disease severity.
After interferon treatment, anti-HDV titers fell markedly in responders; nearly all responders had anti-HDV 1:100 or lower at end of follow-up, whereas relapsers and nonresponders remained at 1:1,000 or higher.
Background
Hepatitis D virus infection remains the most aggressive form of chronic viral hepatitis. Because HDV requires hepatitis B surface antigen (HBsAg) to propagate, it occurs only in people with current hepatitis B virus infection. Clinically, HBV/HDV coinfection or superinfection can accelerate progression to cirrhosis, hepatic decompensation, and hepatocellular carcinoma more rapidly than HBV monoinfection. For this reason, contemporary hepatology practice increasingly emphasizes systematic testing for HDV in HBsAg-positive individuals.
Yet a practical problem persists after anti-HDV positivity is identified: how should clinicians stratify disease activity and monitor treatment? HDV RNA is the principal marker of active viral replication and is indispensable for confirming ongoing infection. However, a single HDV RNA value does not capture the full immunovirologic context, and assay access remains uneven across regions. Anti-HDV is traditionally used as a qualitative diagnostic marker, but its potential quantitative or semiquantitative value in risk stratification has been less well defined.
The study by Ricco and colleagues addresses this gap by examining whether combined measurement of HDV RNA and anti-HDV titers can refine clinical assessment in HBsAg carriers with anti-HDV positivity. The premise is clinically appealing: a virologic marker of active replication paired with a serologic marker of immune exposure may better define who has quiescent infection, who has clinically significant chronic hepatitis D, and who is responding to therapy.
Study Design
Design and population
This was a single-center cohort study including 146 consecutive HBsAg-positive, anti-HDV-positive patients evaluated at baseline. The investigators correlated virologic markers with biochemical, imaging, and histologic indicators of liver disease. A treatment follow-up subgroup of 31 interferon-treated patients had serial measurements at end of therapy, 24 weeks after end of therapy, and end of follow-up.
Laboratory methods
HDV RNA was quantified using the Altostar Quantification Kit from Altona Diagnostics. Anti-HDV was measured by 10-fold endpoint dilutions using the Liaison XL Murex anti-HDV assay from DiaSorin. The study also examined relationships with HBV-related biomarkers, including HBsAg and hepatitis B core-related antigen (HBcrAg), as well as ALT.
Clinical endpoints
The main objectives were to determine how HDV RNA and anti-HDV titers relate to the presence and stage of liver disease, and whether these markers help distinguish treatment responders from relapsers or nonresponders after interferon.
Key Results
Combined biomarker profiling separated low-risk from active disease phenotypes
The most clinically striking finding was the sharp contrast between patients without liver disease and those with chronic hepatitis D. Among 10 patients who were HDV RNA negative and anti-HDV positive, 9 had no liver disease, and all had anti-HDV titers of 1:100 or lower. In contrast, among 136 viremic individuals, only 2 patients, or 1.5%, lacked liver disease; both had very low-level viremia below 500 IU/mL and anti-HDV titers of 1:100 or lower.
This suggests that the combination of absent or minimal viremia and very low anti-HDV titers identifies a small subgroup with limited or no clinically evident hepatic injury. Conversely, active disease was strongly concentrated in patients with higher serologic and virologic burden.
Most patients with chronic hepatitis D had advanced liver disease
Of the remaining 134 patients with liver disease, all were classified as having chronic hepatitis D, and 110 of these 134 patients, or 82.0%, had cirrhosis. This very high prevalence of cirrhosis underlines the severe case mix of the cohort and reinforces the aggressive natural history of HDV infection in referral populations.
Notably, all but one patient with chronic hepatitis D had anti-HDV titers of at least 1:1,000. That finding gives anti-HDV semiquantitation practical relevance: while anti-HDV positivity alone confirms exposure, high titers in this cohort were strongly associated with established liver disease.
HDV RNA tracked with disease severity and liver injury
HDV RNA levels were significantly higher in patients with cirrhosis than in those without cirrhosis. Median values were 5.86 log IU/mL in cirrhotics versus 5.01 log IU/mL in non-cirrhotic patients, with a p value of 0.004. The study also found an intriguing stage-dependent pattern within cirrhosis itself: viremia peaked in early cirrhosis, with median HDV RNA 6.02 log IU/mL, and was lower in advanced cirrhosis, at 5.44 log IU/mL, p=0.006.
This pattern is biologically plausible. In earlier cirrhosis, active viral replication may still be driving necroinflammation and fibrogenesis. In more advanced disease, lower replication may coexist with severe structural liver damage already established, perhaps reflecting loss of functional hepatocyte mass, altered immune control, or survivor bias within a cross-sectional dataset.
Across the cohort, HDV RNA correlated significantly with anti-HDV, HBsAg, HBcrAg, and ALT, all with p values below 0.001. These correlations support the concept that HDV replication is intertwined with HBV surface antigen availability and with biochemical evidence of hepatic inflammation.
Independent associations at multivariable analysis
On multivariate analysis, HDV RNA remained independently associated with liver disease stage, with standardized beta 0.244 and p=0.003; ALT, beta 0.220 and p=0.001; and HBsAg levels, beta 0.515 and p<0.001. The strongest independent association was with HBsAg, which is mechanistically important because HDV depends on HBsAg for virion assembly and propagation.
These data strengthen the argument that HDV RNA is not merely a passive marker of infection but a clinically informative indicator linked to both HBV biology and liver injury severity.
Anti-HDV decline paralleled treatment response
The interferon-treated subgroup offers an important longitudinal perspective. At end of follow-up, all but one of the 16 interferon responders had anti-HDV titers of 1:100 or lower. By contrast, every relapser or nonresponder had anti-HDV titers of 1:1,000 or higher.
This separation is clinically useful because it suggests that anti-HDV may function as a simple adjunctive marker of virologic control over time. Although HDV RNA remains the core measure for antiviral response, falling anti-HDV titers may add confidence that durable suppression has occurred, especially when serial RNA testing is not readily available or when clinicians are interpreting borderline results.
Clinical Interpretation
The main translational value of this study lies in showing that HDV RNA and anti-HDV are complementary rather than redundant. HDV RNA identifies active replication. Anti-HDV titer appears to reflect the broader immunovirologic footprint of infection and, in this cohort, was strongly associated with clinically meaningful disease states.
For frontline practice, three messages stand out. First, low anti-HDV titers at or below 1:100, particularly when HDV RNA is negative or extremely low, may help identify patients with little or no clinically apparent liver disease. Second, high anti-HDV titers, especially 1:1,000 or greater, should raise concern for active chronic hepatitis D and advanced fibrosis or cirrhosis. Third, serial anti-HDV decline during or after therapy may serve as a supportive signal of treatment success.
The correlation with HBsAg is also highly relevant in the era of mechanism-based therapy. HDV remains dependent on HBV envelope protein production, so relationships between HBsAg and HDV RNA are not incidental. This creates a rationale for integrated biomarker monitoring as new anti-HDV and anti-HBV therapeutic combinations are developed.
How These Findings Fit With Current Practice
International guidance from major liver societies already recommends universal or broad anti-HDV screening among HBsAg-positive patients, followed by HDV RNA testing to confirm active infection. The present study does not challenge that framework; rather, it extends it by suggesting that anti-HDV should not be viewed only as a binary screening test.
If confirmed externally, semiquantitative or quantitative anti-HDV assessment could become useful in several settings: triaging anti-HDV-positive patients for expedited specialist evaluation, complementing fibrosis assessment, and supporting longitudinal monitoring after antiviral treatment. This is especially attractive in real-world systems where RNA assays are centralized, costly, or intermittently available.
At the same time, the study should not be interpreted as supporting replacement of HDV RNA with anti-HDV. A patient can remain anti-HDV positive after prior infection or after virologic control. Replication status still requires RNA testing. The clinical opportunity is in combined interpretation.
Strengths and Limitations
Strengths
The study has several strengths. It included a consecutive cohort, reducing some selection bias within the referral setting. Biomarkers were correlated with a robust clinical phenotype including biochemical, imaging, and histologic data. The addition of longitudinal data in interferon-treated patients makes the paper more clinically actionable than a purely cross-sectional analysis.
Limitations
Important limitations should temper interpretation. First, this was a single-center study, so generalizability is uncertain. Referral centers often see more advanced disease, which likely contributed to the exceptionally high cirrhosis prevalence. Second, the treatment subgroup was small, limiting precision in response analyses. Third, anti-HDV was assessed by endpoint dilution on a specific commercial platform; broader adoption will require standardization across assays and laboratories. Fourth, because the study is observational, it establishes association rather than causality.
Another practical limitation is that anti-HDV titer thresholds identified here, such as 1:100 and 1:1,000, may not translate directly to different assays or populations. Before such cutoffs can inform guidelines, multicenter validation with harmonized methods will be essential.
Implications for Research and Therapeutics
The authors appropriately call for prospective multicenter studies. Those studies should test whether combined HDV RNA and anti-HDV measurement improves prediction of clinically important outcomes such as fibrosis progression, hepatic decompensation, hepatocellular carcinoma, and sustained response to therapy.
This research agenda is especially timely. The therapeutic landscape in chronic hepatitis D is changing, with increasing interest in entry inhibitors, immune-based approaches, and combination regimens that target both HDV replication and HBV helper functions. In that setting, biomarker panels capable of distinguishing virologic suppression from true disease modification will become more valuable.
Future work should also clarify how anti-HDV kinetics compare with or add to other emerging markers, including quantitative HBsAg, HBcrAg, and noninvasive fibrosis tools. A clinically useful model might combine these into a treatment-monitoring algorithm that is more informative than any single test.
Conclusion
Ricco and colleagues provide persuasive evidence that combined HDV RNA and anti-HDV measurement offers added value in HBV/HDV coinfection. In this cohort, very low anti-HDV titers together with absent or minimal viremia identified patients who largely lacked liver disease, whereas high anti-HDV titers and higher HDV RNA characterized chronic hepatitis D, frequently with cirrhosis. During interferon follow-up, falling anti-HDV titers tracked closely with durable response.
For clinicians, the practical message is clear: HDV RNA remains essential, but anti-HDV titers may carry underused clinical information. If confirmed in multicenter studies, combined interpretation could improve staging, follow-up, and therapeutic monitoring in one of hepatology’s most severe chronic viral infections.
Funding and Trial Registration
The abstract provided does not report funding information or a ClinicalTrials.gov registration number.
References
Ricco G, Cavallone D, Colombatto P, Coco B, Oliveri F, Damone F, Petralli G, Romagnoli V, Salvati A, Surace L, Calì A, Vianello B, Bonino F, Brunetto MR. Combined HDV RNA and Anti-HDV measurement for the management of HBV/HDV coinfection. Hepatology (Baltimore, Md.). 2026-05-01. PMID: 42065872. URL: https://pubmed.ncbi.nlm.nih.gov/42065872/
European Association for the Study of the Liver. EASL Clinical Practice Guidelines on hepatitis B virus infection. Journal of Hepatology. 2024.
Terrault NA, Lok ASF, McMahon BJ, Chang KM, Hwang JP, Jonas MM, Brown RS Jr, Bzowej NH, Wong JB. Update on prevention, diagnosis, and treatment of chronic hepatitis B: AASLD guidance. Hepatology. 2018.
Hepatitis D International Network and related contemporary reviews have consistently emphasized universal HDV screening in HBsAg-positive individuals and the central role of HDV RNA for confirmation of active infection.
