Anti-HBc

Anti-HBc are antibodies to the hepatitis B virus core antigen (HBcAg). The test shows whether a person has ever been infected with hepatitis B. A positive result indicates past or active infection; other markers, primarily HBsAg and anti-HBs, distinguish these possibilities.

Who is this test for

• people after a risk exposure, when testing alongside HBsAg is needed to determine whether they have ever had hepatitis B infection;
• people with HIV or hepatitis C;
• people with elevated liver enzymes or suspected hepatitis;
• people before chemotherapy, biological or other immunosuppressive therapy and transplantation, because a past infection may reactivate during such treatment;
• adults in risk groups before vaccination, when the doctor wants to know whether they have already had the infection.

What anti-HBc is and what it shows

Hepatitis B is liver inflammation transmitted through blood, sexual contact and from mother to child during birth. It is not transmitted by hugging, kissing, shared cutlery or coughing.

The total anti-HBc test measures all antibodies to the viral core, both IgM and IgG classes. They appear at disease onset, and IgG antibodies remain in blood for life, whether the body clears the virus or infection persists. There is a separate test for recent infection: anti-HBc IgM. This is most often positive in acute infection, usually during the first six months, but may also be positive during a severe flare or reactivation of chronic infection.

Anti-HBc develops only after contact with the virus. The vaccine contains only the viral surface antigen, so vaccination produces the protective antibody anti-HBs, while anti-HBc remains negative. Anti-HBc therefore distinguishes protection acquired through vaccination from that following infection. By itself it does not protect against infection or indicate whether infection is active.

Preparation and sample

Blood is taken from a vein and fasting is unnecessary. If you take biotin (for example, hair and nail supplements), mention this when your blood is drawn, because it may affect some test results.

How results are interpreted

Results are reported as negative (non-reactive) or positive (reactive), sometimes with a numerical index whose threshold depends on the method and is printed on the report. Negative anti-HBc means you have not been infected with hepatitis B unless infection was very recent. The doctor interprets a positive result together with HBsAg and anti-HBs:

HBsAg	Anti-HBc	Anti-HBs	Most common meaning
negative	positive	positive	past infection and naturally acquired protection
positive	positive	negative	acute or chronic infection; anti-HBc IgM and further investigation help distinguish them
negative	positive	negative	isolated anti-HBc; several possibilities, see below
negative	negative	positive	protection acquired through vaccination
negative	negative	negative	no protection or signs of infection; vaccination recommended

If HBsAg is positive for longer than six months, infection is chronic. Most adults recover spontaneously from acute hepatitis B, while chronic infection develops in fewer than 5 % of infected adults; the risk is much higher in young children.

Isolated anti-HBc

When only anti-HBc is positive and HBsAg and anti-HBs are negative, this most often represents a remote infection after which anti-HBs has fallen below the detection threshold over the years. The result may also be false-positive, less commonly indicate recent infection before anti-HBs appears, and rarely an occult infection with very little virus in blood. Depending on your risks, the doctor may recommend repeat testing, anti-HBc IgM, viral genetic material testing (HBV DNA) or vaccination.

Treatment

Acute hepatitis B in adults usually resolves without specific treatment, with monitoring of results. Chronic hepatitis B is treated with antiviral tablets that stop viral replication and reduce the risk of cirrhosis and liver cancer. Treatment is led by an infectious disease specialist or gastroenterologist, and testing and vaccination are recommended for household members and sexual partners of an infected person.

How to arrange testing

You can come for blood collection without an appointment or referral at one of our branches throughout Croatia (listed on the Contact). Prices for anti-HBc and other markers are in the service price list, and an overview of all markers is in the article Hepatitis A, B and C markers.

Frequently asked questions

What does positive anti-HBc mean?

That you were infected with hepatitis B at some point. Most often infection has resolved, particularly if anti-HBs is positive; if HBsAg is positive, infection persists. Positive anti-HBc by itself does not mean chronic disease.

Am I infectious if anti-HBc is positive?

This depends on HBsAg. If HBsAg is negative and anti-HBs positive, infection has resolved and you are not infectious in everyday life. If HBsAg is positive, the virus can be transmitted through blood and sexual contact, so do not share razors or toothbrushes and avoid unprotected sex until speaking to your doctor.

Can anti-HBc be positive after vaccination?

No. Vaccination produces only anti-HBs. If you are vaccinated and anti-HBc is positive, you encountered the virus before or after vaccination.

What is the difference between anti-HBc and anti-HBs?

Anti-HBc shows that a person has been infected, while anti-HBs shows protection. Anti-HBs develops after both vaccination and resolved infection, but anti-HBc only after infection.