No, antiviral medication will not directly affect HBsAg levels.
Thomas
Dear @Barry,
Unfortunately, no test can prove the definitive absence of HBsAg in the blood. Even the most sensitive approved test (qualitative HBsAg) has a limit of detection of 0.02 IU/mL. For quantitative HBsAg its between 0.02 and 0.05 IU/mL.
A report of 0.0 IU/mL (only one decimal place) is not correct reporting for a HBsAg quant result. Its either < 0.05 IU/mL (< LLOQ) or target not detected.
However, even a “target not detected” result does not mean there is no HBsAg present. It just means that the assay cannot detect it.
In your case, your immune control while you were on TDF (which itself also has immunostimulatory properties) was likely causes in some part by your TDF therapy. Removing TDF (even with undetectable HBsAg) must have affected your immune control to the extent where HBV rebound occurred. Although not common, it is possible for people to have their infection rebound after NUC removal following HBsAg loss.
As Thomas pointed out, having HBsAg loss for 6 months while on NUC therapy is a globally accepted endpoint for removal of therapy. Anti-HBs does not figure into this.
Some options moving forward:
1 . Obviously you have to start TDF again. However, what is your HBsAg level?
2. Since you got to HBsAg loss with TDF, you chance of truly achieving functional cure will be improved by adding pegIFN to your TDF therapy. You should discuss this with your doctor.
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Thanks, Thomas and Andrew for your responses.
I don’t know what my current HBsAg level is. The doctor just told me over the phone that my viral load was high and my liver values were elevated. I haven’t seen the results on paper. In any case, I’ve been taking the medication again since Saturday.
What is pegIFN?
Dear @Barry,
Its great that you have started TDF. Everything will come under control in the coming weeks.
PegIFN (short for pegylated interferon alpha 2a) is an immunotherapy approved for the treatment of HBV infection. It is the only approved therapy which can achieve functional cure of HBV. It is not considered a first line therapy anymore becuase it only works in ~6% of patients. However those patients are mostly persons with low HBsAg levels.
Only a few weeks? When I started taking Tenofovir in 2021, it took months for the viral load and liver values to decrease.
I had heard of PegIFN before. But surely my gastroenterologist would have suggested this therapy before if she thought it would work? I also read that it can cause a lot of side effects.
Hi @Barry,
Effects of NUCs start right away (typical reductions are 1-2 log reduction after 4 weeks) but efficient suppression of viral replication is normally established only after a few months of treatment. The point is that you will have the benefit of reduction in viral replication within several weeks which will already help to improve your liver function.
PegIFN is generally well tolerated in HBV infection, especially in the presence of TDF. Side effects are typically limited to flu like symptoms. This is because pegIFN is stimulating immune responses just like when your body encounters other viral infections.
You doctor should be aware that pegIFN has a much higher efficacy rate for functional cure in persons who are able to achieve low levels of HBsAg (as you have experienced on your previous TDF therapy). Should your HBsAg levels become low again, this should be considered.