01Purpose and principlesWhat the assessment is for and the core concepts behind it.
Hepatitis B serology becomes manageable when each marker answers a separate question. Surface antigen (HBsAg) asks whether viral antigen is currently present. Total core antibody (anti-HBc) asks whether natural infection has occurred at some time; vaccination contains surface antigen and therefore does not generate core antibody. Surface antibody (anti-HBs) asks whether circulating immunity is demonstrable. IgM anti-HBc supports recent infection but is not an infallible acute-versus-chronic discriminator. HBeAg and anti-HBe are replication-related markers, while quantitative HBV DNA directly measures viraemia and is essential when infectivity, phase or treatment is being judged.
Classic patterns are useful starting points. Acute infection usually has HBsAg and IgM anti-HBc, with anti-HBs absent. Chronic infection has persistent HBsAg and total anti-HBc, usually without anti-HBs. Resolved natural infection has anti-HBc and anti-HBs without HBsAg. Vaccine immunity has anti-HBs alone. During the uncommon serological window, HBsAg has disappeared before anti-HBs becomes detectable, leaving IgM anti-HBc as the key clue. An isolated total anti-HBc result is not a final diagnosis: repeat or confirm testing, HBV DNA, immune status, country of birth, exposure timing and planned immunosuppression determine its meaning.
Chronic HBV natural history is not a linear march through fixed stages. People move between states of high or low replication and active or inactive hepatic inflammation. HBeAg-positive chronic infection can feature high DNA with limited biochemical activity, while HBeAg-positive hepatitis has active inflammation. HBeAg-negative chronic infection can remain low-replicative, but precore or basal-core-promoter variants cause HBeAg-negative hepatitis with fluctuating DNA and ALT. Fibrosis and HCC can progress even when one clinic result appears quiet. Loss of HBsAg is the most favourable endpoint but does not completely erase HCC risk in established cirrhosis. Coviral hepatitis D should be assessed in HBsAg-positive people according to specialist guidance.
Key points
- HBsAg indicates current HBV infection; persistence for at least six months supports chronic infection rather than a single acute snapshot.
- Total anti-HBc marks natural exposure and is not produced by vaccination, while anti-HBs indicates immunity from recovery or successful vaccination.
- HBsAg-negative, anti-HBc-negative, anti-HBs-positive is the typical vaccine-derived pattern when the history fits.
- HBsAg-negative, anti-HBc-positive, anti-HBs-positive usually represents resolved natural infection but still carries reactivation potential during immunosuppression.
- Anti-HBc IgM supports recent acute infection, yet it can also appear during a severe flare of chronic HBV and must be interpreted contextually.
- HBeAg often indicates higher replication, but HBeAg-negative variants can have active hepatitis and high HBV DNA; measure DNA directly.
- The isolated anti-HBc pattern can reflect remote infection, a window phase, false reactivity or occult infection and deserves risk-based clarification.
- Chronic HBV is dynamic: ALT, HBV DNA, fibrosis, HBeAg status and age or comorbidity together determine phase, prognosis and monitoring.
02Indications, selection and cautionsWhen it is useful, when urgency changes and important limitations.
Recent risk followed by malaise, jaundice, HBsAg and anti-HBc IgM supports acute HBV, but enquire about previous HBsAg because a chronic flare can look identical.
Many HBsAg-positive people feel well and have normal ALT. Country of birth, household or sexual exposure and antenatal screening may provide the only diagnostic clue.
HBsAg-negative, anti-HBc-positive people retain intrahepatic viral templates and can reactivate with B-cell-depleting treatment, stem-cell transplantation or other substantial immunosuppression.
Confusion, hypoglycaemia and increasing INR during acute HBV indicate failing hepatic function and require immediate regional transplant-centre involvement.
Polyarteritis-like vasculitis, glomerulonephritis, arthralgia or rash may accompany HBV; establish viral activity while evaluating other immune and renal diagnoses.
Sexual partners, household contacts, babies born to infected mothers and people sharing injecting equipment may need testing and vaccination through current UKHSA pathways.
03Method and interpretationA systematic approach to the test and its findings.
Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.
- 01
HBsAg with confirmatory testingFirst step - Why
- Establish current surface-antigen positivity and avoid acting on analytical false reactivity.
- Interpretation and limitations
- A confirmed positive result means current infection, not necessarily acute disease. Retrieve earlier results and repeat at the appropriate interval; persistence for at least six months supports chronic HBV.
- 02
Total and IgM anti-HBc - Why
- Identify natural exposure and assess whether infection may be recent.
- Interpretation and limitations
- Total anti-HBc usually persists after natural infection. IgM supports recent acute infection but may occur in a chronic flare; an isolated total anti-HBc result needs context and sometimes HBV DNA.
- 03
Anti-HBs - Why
- Identify surface antibody from recovery or vaccination and assess selected post-vaccination responses.
- Interpretation and limitations
- Anti-HBs alone fits vaccine immunity; anti-HBs with anti-HBc fits resolved infection. Absence of anti-HBs does not by itself prove susceptibility if anti-HBc is present.
- 04
HBeAg and anti-HBe - Why
- Add information about replication phenotype and seroconversion in chronic infection.
- Interpretation and limitations
- HBeAg commonly accompanies higher replication, but HBeAg negativity cannot guarantee low infectivity because variants exist. Always interpret with quantitative HBV DNA and ALT.
- 05
Quantitative HBV DNA - Why
- Measure viraemia for infectivity assessment, phase classification, treatment decisions and response monitoring.
- Interpretation and limitations
- A single level can fluctuate. Interpret logarithmic trends with ALT, fibrosis, cirrhosis and treatment status; detectable DNA despite HBeAg negativity may represent active HBeAg-negative hepatitis.
- 06
ALT, liver reserve and fibrosis assessment - Why
- Identify active injury, advanced disease and complications requiring treatment or surveillance.
- Interpretation and limitations
- Normal ALT does not exclude fibrosis or HCC risk. Use serial values, non-invasive fibrosis testing, ultrasound and specialist assessment rather than one threshold in isolation.
- 07
Hepatitis D, C and HIV testing - Why
- Find coinfection that changes prognosis, treatment and transmission counselling.
- Interpretation and limitations
- Test HBsAg-positive people for HDV according to the specialist pathway, starting with anti-HDV and confirming active infection with RNA where indicated; offer HCV and HIV testing with consent.
04Clinical next stepsHow the result changes management or prompts escalation.
01DecodeRead the marker patternFirst stepHBV screening returns one or more reactive antigen or antibody results.+
- 1Confirm HBsAg reactivity through the laboratory algorithm, assemble HBsAg, total anti-HBc and anti-HBs together, and retrieve vaccination and previous testing history.
- 2Use IgM anti-HBc, HBeAg, anti-HBe and HBV DNA to answer specific timing and replication questions rather than attaching a phase from a single marker.
- 3If the combination is discordant or isolated anti-HBc is present, repeat or confirm tests and seek virology input, especially before immunosuppression, blood donation or pregnancy decisions.
02StageAssess confirmed current infectionHBsAg is confirmed positive or HBV DNA establishes occult active infection.+
- 1Assess symptoms, ALT, bilirubin, albumin, INR, platelets, renal function, quantitative HBV DNA and HBeAg status, and obtain fibrosis and liver imaging appropriate to urgency.
- 2Determine whether infection is acute, chronic or a flare by exposure history, prior results, IgM strength and longitudinal HBsAg, avoiding false certainty from the first sample.
- 3Refer for specialist HBV care, test relevant coinfections including HDV, assess HCC-surveillance eligibility and counsel on transmission, vaccination of contacts and alcohol.
03ProtectPrevent reactivationImmunosuppressive, anticancer or transplantation treatment is planned in a person whose HBV status is unknown or previously resolved.+
- 1Screen with HBsAg and anti-HBc, commonly adding anti-HBs, before immunosuppression begins; do not rely on liver tests or a past vaccination history alone.
- 2For any HBsAg-positive or anti-HBc-positive result, define HBV DNA and treatment-specific reactivation risk with hepatology, virology and the prescribing specialty before the first dose when possible.
- 3Use prophylactic antiviral treatment or intensive monitoring as the agreed risk pathway requires, and continue surveillance after immunosuppression because reactivation can be delayed.
05Risks, monitoring and follow-upComplications, safety checks and further assessment.
- For confirmed chronic infection, follow ALT, HBV DNA, HBeAg or anti-HBe where relevant, liver reserve and fibrosis at intervals set by phase and specialist guidance.
- Repeat apparently inactive profiles longitudinally because HBeAg-negative hepatitis can fluctuate and a single normal ALT or low DNA result may misclassify disease.
- Deliver six-monthly HCC surveillance when indicated by cirrhosis or the NICE HBV risk criteria, even when antiviral suppression is excellent.
- During reactivation-risk immunosuppression, monitor HBV DNA and ALT or provide prophylaxis for the treatment-specific duration agreed with specialists.
- Document partner and household contact testing, vaccination and public-health advice without disclosing the patient's diagnosis beyond lawful and consented pathways.
- Reassess urgently for jaundice, coagulopathy, encephalopathy or a marked ALT flare, particularly after treatment interruption or immune reconstitution.
06Special situationsVariants, exceptions and circumstances that change the usual approach.
Core means encounter
Because licensed hepatitis B vaccines contain surface antigen rather than core antigen, anti-HBc is evidence of natural viral exposure rather than vaccination.
Surface antibody has context
Anti-HBs means something different beside anti-HBc: without core antibody it suggests vaccine immunity, while with core antibody it usually marks recovery from infection.
E antigen is imperfect
HBeAg is a useful replication marker, but viral variants can replicate actively without producing it, so HBV DNA is the direct measurement needed for decisions.
Resolved is not eradicated
Covalently closed circular HBV DNA can persist in hepatocytes after HBsAg loss, explaining reactivation under profound immune suppression.
Natural history fluctuates
Phase labels describe the current relationship between virus and host; they should be revised when serial ALT, DNA, fibrosis or antigen status changes.
07Common pitfallsFrequent interpretation and management errors.
- 01
Calling anti-HBs positivity alone evidence of previous natural infection without checking anti-HBc.
- 02
Assuming HBeAg negativity means no replication or negligible transmission risk.
- 03
Diagnosing acute HBV from IgM anti-HBc without considering a severe flare of chronic infection.
- 04
Ignoring isolated anti-HBc before rituximab, stem-cell transplantation or other high-risk immunosuppression.
- 05
Using one normal ALT and low HBV DNA result to discharge a chronically infected person permanently.
- 06
Forgetting HDV assessment, fibrosis staging and HCC-risk review after confirming HBsAg positivity.