Among patients exposed to HBV, an isolated positive anti-HBc result might be the result of loss of anti-HBs after past resolved infection, occult infection (i.e., HBsAg is negative, but HBV DNA is positive), being in the window period before appearance of anti-HBs, or an HBsAg mutant infection (i.e., an infection that is not picked up by an HBsAg test unable to detect mutants). Here, KRT88P is linked to infection.