Anti-HDV immunoglobulin M testing in hepatitis delta revisited: correlations with disease activity and response to pegylated interferon-α2a treatment.

BACKGROUND: The role of anti-HDV immunoglobulin M (IgM) testing in patients receiving pegylated interferon-α therapy for hepatitis delta is unknown. We performed anti-HDV IgM testing in a well defined cohort of HDV-infected patients who were treated with pegylated interferon-α2a plus adefovir, or either drug alone.
METHODS: Sera from 33 HDV-RNA-positive patients from the international HIDIT-1 trial were available for anti-HDV IgM testing (ETI-DELTA-IGMK-2 assay, DiaSorin, Saluggia, Italy) before therapy, at treatment weeks 24 and 48, and at 24 weeks after the end of treatment.
RESULTS: Anti-HDV IgM tested positive in 31 out of the 33 patients (94%) prior to treatment. HDV IgM levels correlated with histological inflammatory activity (r=0.51, P<0.01) and were higher in patients with alanine aminotransferase and γ-glutamyl transpeptidase levels above the median (P<0.05). Quantitative anti-HDV IgM values declined in patients responding to antiviral therapy, however anti-HDV IgM remained positive after treatment in the majority of virological responders.
CONCLUSIONS: We suggest that anti-HDV IgM testing might give additional useful information to determine disease activity in hepatitis delta and to predict treatment response to antiviral therapy with type I interferons. However, determination of anti-HDV IgM can not substitute HDV RNA testing, which remains the primary virological marker for response to therapy.