Baseline HBsAg, platelet count predict spontaneous HBsAg seroclearance

Aug 4 2015

By Shreeya Nanda, Senior medwireNews Reporter

Hepatitis B surface antigen (HBsAg) level and platelet count at baseline are significantly associated with spontaneous HBsAg seroclearance in hepatitis B virus (HBV) carriers and those with chronic infection, research suggests.

Among 634 participants who were positive for HBsAg but negative for hepatitis B e antigen, 18.45% attained HBsAg seroclearance at 6 years, equating to a yearly seroclearance rate of 3.08%.

As this annual rate is considerably higher than those reported in previous studies (0.5–1.4%), Zhen-ge Han (Guanghua Hospital of Traditional and Western Medicine, Shanghai, China) and co-workers suggest that “seroclearance may not be as rare as previously thought”.

Spontaneous HBsAg loss occurred in 79.1% of 129 participants with baseline HBsAg levels below 10 IU/mL, 9.8% of 143 with baseline HBsAg levels of 10 IU/mL or above but less than 200 IU/mL, and 0.3% of 362 with baseline HBsAg levels of at least 200 IU/mL.

And binary logistic regression analysis showed that baseline HBsAg levels below 200 IU/mL or 10 IU/mL were significantly associated with spontaneous HBsAg clearance (p<0.001 for both) as was the platelet count at study enrolment (p=0.004), with lower HBsAg levels and higher platelet count correlating with a higher rate of HBsAg seroclearance.

Of these, baseline HBsAg levels predicted 6-year HBsAg seroclearance significantly better than initial platelet count, with an area under the receiver operating characteristic curve of 0.965 versus 0.617 (p<0.001).

Moreover, the 10 IU/mL cutoff predicted 6-year HBsAg loss with a diagnostic accuracy of 93.4%, a sensitivity of 87.2%, a specificity of 94.8%, a positive predictive value of 79.1% and a negative predictive value of 97.0%. The corresponding values for the 200 IU/mL threshold were 75.2%, 99.1%, 69.8%, 42.6% and 99.7%, respectively.

The study authors write in the Journal of Medical Virology that the 10 IU/mL compared with the 200 IU/mL cutoff “could better predict subsequent HBsAg loss at 6 years”, which they say has “implications for practicing physicians intending to determine the odds of HBsAg loss”.

But Han et al note that two of the 117 participants who achieved HBsAg seroclearance remained positive for HBV DNA at the end of the study, suggesting that “HBsAg loss [is] not completely equivalent to recovery from chronic HBV infection”.

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