Hbsag Screen

Overview

An HBsAg screen is a simple blood test. It checks whether the hepatitis B virus is in your body right now. HBsAg stands for 'hepatitis B surface antigen'. An antigen is a small piece of a virus that your immune system can recognise. So this test is looking for a protein that sits on the outside of the hepatitis B virus. Hepatitis B is a virus that infects the liver. Many people who have it feel completely well and do not know it, which is exactly why a screening test can be useful. The result on its own does not tell the whole story — doctors usually read it together with a few other blood tests.

The test itself is very common — it is used in antenatal care, blood donation, travel and immigration health checks, and routine screening in many countries. Hepatitis B is also common worldwide: hundreds of millions of people are living with long-term (chronic) infection, and many do not know it. In the UK and similar countries, new infections are much less common, but screening is still offered to people with risk factors.

Anyone can catch hepatitis B, so anyone can be offered this test. Screening is especially recommended if you were born in, or have lived for a long time in, a part of the world where hepatitis B is common (for example parts of Asia, Africa, Eastern Europe, the Middle East, South America and the Pacific islands); if you are pregnant; if you live with someone who has hepatitis B; if you inject drugs or have ever shared needles; if you are a man who has sex with men; if you have had many sexual partners; if you have HIV or another condition that affects your immune system; if you are having kidney dialysis; if you work in healthcare or another job where needle injuries can happen; or if you have ever had unusual liver blood tests. Blood and organ donors are also screened.

Symptoms

Common symptoms

• Often no symptoms at all — this is very common, especially in children and in people with long-term infection
• Feeling very tired or washed out
• Feeling sick (nausea) or being sick, and going off food
• Aches and pains, sometimes joint aches
• A mild temperature and feeling generally unwell, a bit like flu
• Pain or discomfort under the ribs on the right side, where the liver sits
• Yellowing of the skin or the whites of the eyes (this is called jaundice), dark urine, and pale, chalky stools
• Itchy skin

Symptoms in children

• Most children have no symptoms at all, or only very mild ones
• Babies and young children who catch hepatitis B are much more likely than adults to stay infected long term, but they usually look and feel well
• Because symptoms are often absent, testing — rather than symptoms — is what picks up infection in children

Symptoms in older adults

• Tiredness that is put down to 'just getting older' can sometimes be the only clue
• If a liver is already damaged by another cause (such as long-term alcohol use or fatty liver), the effects of hepatitis B can add up
• Yellowing of the eyes can be easier to miss in some skin tones, so other signs such as dark urine or pale stools matter

Causes

Main causes

• Hepatitis B is caused by the hepatitis B virus. It spreads when blood, semen, vaginal fluid, or other body fluid from someone with the virus gets into another person's body
• Sex without a condom with someone who has the virus
• Sharing needles or other equipment to inject drugs, including steroid injections
• A mother passing the virus to her baby during childbirth — this is why pregnant women are offered screening
• Sharing razors, toothbrushes or nail clippers, which can carry tiny amounts of blood
• Medical, dental, tattooing or piercing equipment that has not been properly sterilised
• A needle or sharp injury at work, for example in healthcare
• You cannot catch hepatitis B from hugging, kissing, holding hands, sharing food, coughing or sneezing

Risk factors

• Being born, or living for a long time, in a region where hepatitis B is common
• Having a parent, child, housemate or sexual partner with hepatitis B
• Being pregnant — screening protects your baby
• Injecting drugs, now or in the past
• Being a man who has sex with men, or having many sexual partners
• Having HIV or another condition, or taking treatment, that weakens the immune system
• Kidney dialysis or regular blood products
• Working in healthcare, dentistry, or another job where needle injuries happen
• Having ever had liver blood tests that looked unusual
• Living in a closed setting such as a prison

When to see a doctor

See a doctor urgently if:

• You think you may have been exposed to hepatitis B recently — contact a sexual health clinic, your GP, or an emergency department straight away, because treatment to prevent infection works best within the first day or two
• You have yellow skin or eyes, dark urine with pale stools, or severe tummy pain
• You have a needle or sharp injury at work
• You are pregnant and have never been screened for hepatitis B

Book a routine appointment if:

• You would like to know your hepatitis B status because of any risk factor listed above
• You are planning a pregnancy, or you are pregnant
• You are about to start treatment that can affect the liver, or that weakens the immune system
• You are a household or sexual contact of someone who has just been told they have hepatitis B
• You have felt unusually tired for weeks and your doctor is looking for causes
• You are travelling or moving to a country where hepatitis B is common and want to check your immunity or get vaccinated
• You are thinking of donating blood, sperm or an organ

Diagnosis

The HBsAg screen is done on a small blood sample taken from a vein in your arm, usually at a GP surgery, sexual health clinic, antenatal clinic or hospital. The sample goes to a laboratory and the result usually comes back within a few days to a couple of weeks. If the HBsAg result is positive, your doctor will usually request extra tests to work out whether the infection is new or has been there a long time, how active the virus is, and how well your liver is coping. If it is negative but you have a risk factor or a recent possible exposure, your doctor may suggest repeating it later.

Tests that may be done

• HBsAg (hepatitis B surface antigen) — the screening test itself
• Anti-HBs — an antibody test that shows whether you are protected, either from vaccination or from a past infection you have cleared
• Anti-HBc (core antibody), sometimes with an IgM version, to help show whether infection is recent or long-standing
• HBeAg and HBV DNA (viral load) — these show how actively the virus is multiplying
• Liver function blood tests to see how your liver is working
• A liver ultrasound scan, or a FibroScan (a quick, painless scan that measures stiffness in the liver)
• Sometimes other blood tests for hepatitis A, C, D and HIV, since these can overlap
• Occasionally a small liver biopsy, though this is needed much less often than in the past

What to expect at your appointment

You may feel a brief pinch when the needle goes in, and there may be a small bruise afterwards. You can usually drive, work and eat normally straight away. Some clinics ask you to avoid heavy exercise for a few hours. If other blood tests are being done at the same time, you may be asked whether to fast — check when you book. Your result is confidential. Ask the person giving you the result to explain exactly what it means and what happens next, and ask for it in writing if that helps you remember. A screening test on its own is never the whole picture, so it is fine to ask, 'What does this mean for me?'

Treatment

What happens next depends entirely on your results. If the test shows you are protected, nothing further is needed apart from routine care. If it shows a new infection, most healthy adults clear hepatitis B on their own within a few months with rest, fluids and monitoring. If it shows a long-term (chronic) infection, the aim is to protect your liver: regular check-ups, blood tests and sometimes scans, with treatment if the virus is active or the liver is being affected. There is no need to make any decisions before you have your results and have talked them through.

Self-care at home

• Rest and drink plenty of fluids if you feel unwell, and give yourself time to recover
• Avoid alcohol while there is any question about your liver — your clinician can tell you when it is safe again
• Check with a pharmacist before taking any over-the-counter medicine, including painkillers and cold remedies, because some are hard on the liver
• Do not share razors, toothbrushes, nail clippers, needles or injecting equipment
• Tell current and past sexual partners so they can be tested and, if needed, vaccinated — clinics can help you do this discreetly
• Make sure everyone you live with is tested and vaccinated
• Keep a note of your results and test dates so you can show them to any new doctor
• Go to your follow-up appointments even if you feel completely well — this is how problems are caught early

Medical treatments

Treatment is decided by a specialist, usually a liver or infectious diseases team, based on your blood tests and liver scans. For a new infection, treatment is often 'watch and wait', because the body usually clears the virus. For long-term infection, doctors may use antiviral medicines that slow or stop the virus from multiplying; these are taken as tablets and are usually well tolerated, and the specialist will explain the options, the possible side effects and how long treatment might last. Monitoring is a treatment in its own right: regular blood tests and scans catch changes early. Vaccination of partners and household members is part of the plan too. This article does not recommend any particular medicine — your specialist team will discuss what suits you.

When is surgery considered?

Surgery is not needed for hepatitis B itself. In rare cases, if the liver has been badly damaged over many years, a liver transplant may be considered, and liver doctors treat liver cancers that can develop with long-term infection. Most people with hepatitis B never need an operation.

Living with this condition

Most people with hepatitis B, whether they clear it or live with it long term, get on with work, study, family life and travel much as before. The main practical change is keeping up with check-ups and being mindful about blood contact — using your own razor and toothbrush, and telling sexual partners so they can be protected. Hepatitis B is not spread by everyday contact, so you do not need to isolate, avoid sharing meals, or worry about hugging people you care about. You do not usually need to tell your employer, but you should tell any doctor, dentist or nurse who treats you, and there are rules about working in some healthcare procedures — your occupational health team can advise.

Lifestyle tips

• Keep up with appointments and blood tests, even when you feel well
• Avoid alcohol, or keep well within national guidance — your clinician can advise what is safest for your liver
• Never share needles or injecting equipment; needle exchange services are free, confidential and non-judgemental
• Use condoms until partners have been tested and vaccinated
• Keep razors, toothbrushes and nail clippers separate
• Get vaccinated against hepatitis A if your clinician advises it, as it protects the liver further
• Tell your dentist and any doctor treating you about your hepatitis B status
• Cover cuts and grazes, and clean up blood spills with gloves

Diet and exercise

A balanced, everyday diet is the goal — plenty of vegetables, fruit, wholegrains, beans, eggs, fish and lean meat, and not too much sugar or fried food. There is no special 'liver diet' that cures hepatitis B, but keeping to a healthy weight takes pressure off the liver, since fatty liver and hepatitis B together are harder on it. Aim for regular moderate activity you enjoy — walking, swimming, cycling, gardening — most days if you can. If you feel very tired during a flare-up, rest and gentle movement are fine, and build up again slowly.

Mental health and emotional wellbeing

Being told you have a virus that can be passed on can bring up a lot: worry about your health, fear of judgement, shame, or feeling you cannot talk to anyone. These feelings are common and understandable, and they usually ease once you have a clear plan and someone to talk things through with. Getting accurate information helps more than searching online at 2am. If low mood, anxiety or worry is affecting your sleep, work or relationships, tell your clinician — support such as counselling is available. If you ever feel overwhelmed or have thoughts of harming yourself, contact your local crisis line or emergency services straight away; you deserve immediate help and you do not have to cope alone.

Prevention

Yes. Hepatitis B is one of the few viruses that can be prevented by vaccination, and the vaccine works very well. Beyond vaccination, the main protections are using condoms with new partners until everyone has been tested, never sharing needles or injecting equipment, using sterile equipment for tattoos and piercings, and not sharing razors or toothbrushes. Pregnant women are offered screening so that a baby at risk can be protected at birth.

Vaccines

The hepatitis B vaccine is given as a course of injections over a few months, and it protects most people for many years. In the UK it is offered to all babies as part of routine childhood immunisations, and to adults at higher risk — including healthcare workers, people with liver conditions, close contacts of someone with hepatitis B, people who inject drugs, men who have sex with men, and people travelling to higher-risk countries. If you were vaccinated long ago or are unsure whether you are protected, a simple antibody blood test can tell you, and a booster can be arranged if needed.

Screening programmes

Screening programmes exist to find hepatitis B in people who feel well. In the UK, all pregnant women are offered the test as part of antenatal care, and blood, organ and sperm donors are screened. Many countries also screen people in higher-risk groups, people starting certain treatments, and people in prisons. If you think you may be in a group that is offered screening and have never been tested, it is worth asking — the test is quick and free on the health service.

Complications

If left untreated

• Long-term (chronic) infection, which is more likely the younger you were when infected
• Scarring of the liver, called cirrhosis, which can build up over many years without symptoms
• Liver cancer, which is why people with long-term hepatitis B are offered regular scans
• Liver failure in severe cases
• Passing the virus on to other people without knowing it
• Extra strain on the body if the liver is already affected by alcohol, fatty liver or another hepatitis virus

Long-term outlook

The outlook is genuinely good for most people. Around 9 in 10 healthy adults who catch hepatitis B clear the virus on their own within about six months and are then immune for life. Of those who do develop long-term infection, many stay well for decades, and regular monitoring means any change in the liver is picked up early, when it can be managed. Modern antiviral treatment can keep the virus under control and protect the liver. Being tested is the step that opens the door to all of this — it is information that helps you and your doctor look after you well.

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