Is It Time To Start Testing HBsAg Levels in Hep B Patients?

Two recent studies show that HBsAg levels may help determine therapeutic decisions:

  • WP Brower et al. Clin Gastroenterol Hepatol 2016; 14: 1481-89
  • Y-C Hsu et al. Clin Gastroenterol Hepatol 2016; 14: 1490-98.

The first study was a retrospective study of 292 HBeAg-negative patients with chronic hepatitis B virus (HBV) infection.  This cohort had normal ALT values and HBV DNA <20,000 IU/mL.  Patients were considered to be carriers of inactive HBV if their HBV DNA was <2000 IU/mL and serum levels of ALT remained normal.

Key findings with regard to likelihood of having inactive HBV at following year:

  • “odds were 97% for initial level of HBsAg <100 IU/mL”
  • “odds were 85% for patients with initial levels 100-1000 IU/mL and 76% for patients with initial levels >1000 IU/mL”

Also, “patients with HBV activity who had levels of HBV DNA <5000 IU/mL and decreases in HBsAg of 0.5 log IU/mL or more for 1 year had a high probability of becoming carriers of inactive HBV in the next year.” Figure 2 in an easy graphic form shows cumulative probabilities of becoming inactive or active HBV over the three-year period.

In the second study, Hsu et al performed a prospective study of 161 consecutive patients with undetectable HBV DNA following 3 or more years of entecavir.  After stopping therapy, patients were monitored for relapse.

Key findings;

  • 49.2% of patients had a clinical relapse (defined by elevation of both HBV DNA >2000 IU/mL and by elevated ALT >2-fold ULN)
  • 81.7% had virological relapse (HBV DNA >2000 IU/mL).
  • All patients with HBeAg-positivity had clinical relapse and were retreated.
  • For HBeAg negative patients at end of treatment, 39.2% had a clinical relapse & 77.4% had a virological relapse.
  • Serum HBsAg level predicted relapse among HBeAg-negative patients: 11 patients with HBsAg <10 IU/mL did not relapse. The lower the serum level of HBsAg at the end of treatment, the lower the rate of clinical relapse (see Figure 1).  Of those with HBsAg 100-1000, there was ~25% clinical relapse at 30 months f/u and more than 50% virological relapse.

My take: HBsAg level is becoming important in truly determining who has inactive HBV and reflects the likely natural history.  It is expected that using HBsAg levels will be increasingly used to determine management of HBeAg-negative HBV.

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