Just came across an old paper.
Decreasing Levels of HBsAg Predict HBsAg Seroclearance in Patients With Inactive Chronic Hepatitis B Virus Infection
CONCLUSIONS: The decrease in the level of HBsAg accelerates during the 3 years before HBsAg seroclearance. Levels of HBsAg of 200 IU/mL or less have high NPVs for HBsAg seroclearance; PPVs increase to 97% to 100% when combined with a 1 log IU/mL or more decrease in level of HBsAg over a 2-year period.
https://www.cghjournal.org/article/S1542-3565(11)00917-7/pdf