Hepatitis Serologies | Bone Wizardry

Marker Key

What Each Marker Actually Means

Hover any term for the mechanism. The markers have personalities · learn them.

HBsAg · Surface Antigen

The viral surface coat protein, actively shed into blood. Present = actively infected. Appears first (1-10 weeks post-exposure), disappears by ~6 months in acute infection. If it's still positive at 6 months → chronic.

Memory: Surface Antigen = Still infected. Both start with S.

anti-HBs · Antibody to Surface Antigen

Protective neutralizing antibody. Positive = immune. Appears after HBsAg clears (or after vaccination). This is the only marker the vaccine generates.

Memory: anti-HBs = Safe. Surface antibody = shield = you're good.

anti-HBc IgM · IgM Core Antibody

ACUTE infection marker. IgM = immediate/early immune response. Appears ~1 month post-exposure. The only positive marker during the window period · this is why it's high yield. Goes away in ~6 months as IgG takes over.

anti-HBc IgG · IgG Core Antibody

Chronic marker / "been there". Indicates past or ongoing infection. Persists for life after any HBV exposure. NOT produced by the vaccine · this is how you tell "recovered from infection" vs "vaccinated."

HBeAg · e Antigen

Secreted viral core protein that reflects active viral replication. High HBeAg = high viral load = high infectivity. Seroconversion (HBeAg → anti-HBe) marks viral control in chronic infection. Loss of HBeAg with treatment = good sign.

The Core

The 5 HBV Serology Scenarios

These are the 5 patterns boards test. All expanded · study the tables.

1

Acute Infection

Symptomatic, within first 6 months

Marker	Result	Why
HBsAg	+	Virus is present, surface coat being shed
anti-HBc IgM	+	Acute = IgM. Always positive in acute HBV.
anti-HBs	−	Can't have HBsAg and anti-HBs at same time
HBeAg	+	Active replication = high infectivity
anti-HBc IgG	−	IgG takes months to develop

Board Pearl

HBsAg + anti-HBc IgM together = acute HBV. Don't need anything else.

Most adults clear acute HBV spontaneously (95%). Progression to chronic is higher in neonates (90%) and immunocompromised.

2

Window Period

The board trap. Know this cold.

Most-Tested Board Trap

HBsAg has cleared. anti-HBs hasn't formed yet. If you only look at those two, this patient looks uninfected. That's the trap.

Marker	Result	Why
HBsAg	−	Antigen cleared · immune system won
anti-HBs	−	Not formed yet · immune system is catching up
anti-HBc IgM	+	The ONLY clue. This is what saves you.
anti-HBc IgG	−	IgG hasn't kicked in yet

Anti-HBc IgM alone = window period. Patient is still infected but in a serological gap.

The window lasts weeks to months. These patients are still infectious. Don't clear them for blood donation.

3

Recovered / Immune (Prior Infection)

Cleared the virus, has lifelong markers

Marker	Result	Why
HBsAg	−	Virus cleared
anti-HBs	+	Protective antibody formed after clearance
anti-HBc IgM	−	IgM fades · acute phase is over
anti-HBc IgG	+	Marker of prior exposure. Persists forever.

anti-HBs + anti-HBc IgG = recovered from natural infection. This pattern distinguishes from vaccination.

These patients have lifelong immunity and do not need vaccination. anti-HBc IgG is the fingerprint that says "I was actually infected."

4

Vaccinated / Immune (No Prior Infection)

Only one marker is positive

Marker	Result	Why
HBsAg	−	Never infected
anti-HBs	+	Vaccine generates anti-HBs ONLY
anti-HBc IgM	−	Never infected = no core antibody
anti-HBc IgG	−	Never infected = no core antibody
HBeAg	−	Never infected

anti-HBs ALONE = vaccinated. No anti-HBc IgG. That's the entire key to separating vaccinated from recovered.

The HBV vaccine is a recombinant surface antigen vaccine · it only teaches the immune system to recognize HBsAg. So anti-HBs is the only antibody produced.

5

Chronic Active Infection

HBsAg positive >6 months

Marker	Result	Why
HBsAg	+	Still present >6 months = chronic by definition
anti-HBs	−	Can't coexist with HBsAg
anti-HBc IgM	−	IgM is acute · faded after 6 months
anti-HBc IgG	+	Chronic = ongoing exposure = IgG persists
HBeAg	±	Positive = actively replicating (high infectivity)

HBsAg + anti-HBc IgG (no IgM, no anti-HBs) = chronic HBV. The absence of IgM confirms it's not acute.

HBeAg+ in chronic = high viral load, high infectivity. HBeAg− in chronic = "inactive carrier" · lower viral load but still HBsAg+.

Board Pearl

Chronic HBV → risk for cirrhosis + hepatocellular carcinoma. Annual ultrasound + AFP surveillance.

Memory Hooks

Tap to Reveal

Max 2. These are designed to stick.

🔑

How do I remember HBsAg vs anti-HBs?

S = S rule.
Surface Antigen = Still infected.
anti-HBs = Safe.

Antigen present? Still sick. Antibody to surface? You're protected. The letters tell you.

tap

🔑

Vaccinated vs Recovered · how do I tell them apart when both have anti-HBs+?

Core = was actually there.
Vaccine never touches the core. No HBcAg in the vaccine = no anti-HBc ever.

So: anti-HBs alone = vaccinated.
anti-HBs + anti-HBc IgG = recovered.

If they have a core antibody, the virus was inside them. Period.

tap

Visual Reference

HBV Infection Timeline

When markers appear and disappear over a typical acute → recovery course.

Window period = HBsAg cleared, anti-HBs not yet formed → anti-HBc IgM is the only positive

Elimination Game

Match the Panel

See a serology result. Eliminate scenarios. Name the diagnosis. This is how it works on test day.

Score: 0 / 0

Quick Reference

The Hepatitis Alphabet

HAV, HBV, HCV, HDV, HEV · what makes each one different.

Virus	Nucleic Acid	Transmission	Chronic?	High Yield Fact
HAV	RNA	Fecal-oral Contaminated food/water. Shellfish (filter feeders concentrate virus). Daycare outbreaks, travel to endemic areas.	No · always self-limited	anti-HAV IgM = acute. anti-HAV IgG = immune. No carrier state.
HBV	DNA	Blood/sexual/perinatal	Yes · 5-10% adults, 90% neonates	5 serology scenarios. Window period. Vaccine = anti-HBs only. DNA virus (only hepatitis DNA virus you need to know).
HCV	RNA	Blood-borne (IVDU, transfusion pre-1992)	Yes · 75-85% go chronic	Most common chronic blood-borne infection in USA. No vaccine. Tx: direct-acting antivirals (sofosbuvir). anti-HCV = exposed (not protective · test for RNA to confirm active).
HDV	RNA	Blood/sexual (needs HBV co-infection)	Yes if co-infect	Delta virus · defective HDV is an incomplete virus. It REQUIRES HBsAg as its envelope to replicate. No HBV = no HDV. HBV vaccination prevents HDV co-infection. . Two patterns: co-infection (HBV+HDV together, usually clears) vs superinfection (HDV on chronic HBV → fulminant).
HEV	RNA	Fecal-oral Endemic in Southeast Asia, Central America, Africa. Major outbreaks from contaminated water. Pigs are a reservoir.	No · self-limited (except pregnancy)	Catastrophic in pregnancy · 20% mortality in 3rd trimester. "Pregnant woman returns from India with liver failure" = HEV until proven otherwise. Like HAV but deadlier in pregnancy.

RNA vs DNA · just one to know

HBV is the only DNA hepatitis virus in this list. HAV, HCV, HDV, HEV are all RNA. Don't overcomplicate it · boards just want you to know HBV = DNA.

Fecal-oral group: HAV and HEV · both RNA, both self-limited (mostly), both via contaminated water/food. The difference: HEV kills pregnant women. HAV doesn't.

Blood-borne chronic group: HBV and HCV · both go chronic, both can cause cirrhosis + HCC. HCV more often goes chronic. HBV has a vaccine; HCV doesn't.

Pattern Cards

The 5 HBV Patterns

Tap each card to flip and see the full serology pattern. These are the 5 boards tests you on repeat.

ACUTE

Acute Infection

0-6 months post-exposure

tap to flip

HBsAg	+
anti-HBs	-
anti-HBc IgM	+
anti-HBc IgG	-
HBeAg	+

IgM core = acute. HBeAg = replicating.

WINDOW

Window Period

The board trap

tap to flip

HBsAg	-
anti-HBs	-
anti-HBc IgM	+
anti-HBc IgG	-
HBeAg	-

IgM alone = window. Still infected.

RECOVERED

Recovered

Natural infection cleared

tap to flip

HBsAg	-
anti-HBs	+
anti-HBc IgM	-
anti-HBc IgG	+
HBeAg	-

anti-HBs + anti-HBc IgG = was infected, now immune.

VACCINATED

Vaccinated

No prior infection

tap to flip

HBsAg	-
anti-HBs	+
anti-HBc IgM	-
anti-HBc IgG	-
HBeAg	-

anti-HBs alone. No core Ab = never infected.

CHRONIC

Chronic Active

HBsAg positive >6 months

tap to flip

HBsAg	+
anti-HBs	-
anti-HBc IgM	-
anti-HBc IgG	+
HBeAg	+/-

HBsAg + IgG (no IgM) = chronic. IgG stays forever.

Decision Tree

HBV Serology Interpreter

See a result set. Click your way to the diagnosis. This is how test day works.

Is HBsAg positive?

Memory Hooks

Tap the Hook, Lock the Fact

Five triggers. Five board locks. Tap any yellow term to get the hook.

The Window PeriodHBsAg cleared, anti-HBs not formed yet. ONLY anti-HBc IgM is positive. "The window" = you can see through from one side but there's no glass yet. Still infected, still infectious. is the highest-yield HBV trap on boards. The S-S RuleS = Surface Antigen = Still infected. anti-HBs = Safe. Both start with S. If HBsAg is present, the patient is still sick. If anti-HBs is present, they're safe. keeps HBsAg and anti-HBs straight. The Core Fingerprintanti-HBc IgG stays positive for life after ANY real HBV infection. The vaccine NEVER generates it. If they have core IgG, the virus was inside them. Period. This separates recovered from vaccinated when both have anti-HBs+. separates the recovered patient from the vaccinated one. HBeAg = ReplicationHBeAg is a secreted core protein. Present = virus is actively replicating. High viral load. High infectivity. In chronic HBV, HBeAg seroconversion to anti-HBe is a treatment milestone. "e" for enzyme of replication = you can think of it as the engine light. tells you if the virus is running hot. And DNA = HBVHBV is the ONLY DNA hepatitis virus. HAV, HCV, HDV, HEV are all RNA. HBV = Hepatitis B Virus = DNA Breaks Virus alphabetically: B comes before all RNA ones. One DNA, four RNA. is the only classification fact boards test on the alphabet.

Hook 01

Tap the window

Tap: Window = IgM aloneWhen both HBsAg and anti-HBs are negative, the only thing that reveals the truth is anti-HBc IgM. Like a window with no glass. You can see the room (the patient has HBV) but there's no solid barrier yet (anti-HBs). The window lasts weeks to months.

Hook 02

Vaccine vs. Recovered

Tap: No core = never infectedVaccinated patients have anti-HBs ONLY. No anti-HBc. Ever. The HBV vaccine is a surface antigen inject. It never exposes the immune system to the core. So anti-HBc requires real infection. Simple rule: core antibody = virus was there.

Hook 03

Chronic definition

Tap: Chronic = HBsAg >6 monthsIf HBsAg is still positive 6 months after the initial infection, the patient is chronic. That's it. No other test needed for the definition. IgM will be gone by then (replaced by IgG). No anti-HBs (can't coexist). Annual ultrasound + AFP for HCC surveillance.

Hook 04

HEV in pregnancy

Tap: HEV kills mothersHEV is fecal-oral, self-limited in most adults. But in the 3rd trimester of pregnancy, mortality is up to 20%. Mechanism: unclear, likely immune tolerance shifts. Vignette = pregnant woman returning from endemic area (India, SE Asia) + liver failure = HEV until proven otherwise.

Hook 05

HDV is a satellite virus

Tap: HDV needs HBsAg to replicateDelta virus can't make its own coat. It hijacks HBsAg as its outer envelope. No HBV = no HDV. Vaccinating against HBV automatically protects against HDV. HDV superinfection on chronic HBV = worst outcome: fulminant hepatitis + high cirrhosis rate.

Clinical Images

Hepatitis Pathology Gallery

Wikimedia Commons. Tap any image to expand.

Decision Tree

Interpreting Hepatitis B Serology

Start with HBsAg. Follow the branches. Each endpoint tells you what to do clinically.

Is HBsAg positive?

Virus is present. Now determine: acute or chronic? Check anti-HBc IgM.

Acute HBV infection. Supportive care; most adults clear spontaneously (95%). Monitor LFTs and HBsAg. Antiviral therapy reserved for fulminant cases. Notify contacts and test them.

Chronic HBV infection. Check HBeAg and HBV DNA. High viral load (HBV DNA above 2000 IU/mL) or active hepatitis: treat with tenofovir or entecavir. Annual ultrasound plus AFP for HCC surveillance. Vaccinate household contacts.

No active virus detected. Now check anti-HBs and anti-HBc to determine immune status.

Past natural infection, now immune. Virus cleared, protective antibody formed. Core IgG is the fingerprint that proves real virus was present. No treatment needed. Cannot donate blood (core antibody flags blood banks).

Successfully vaccinated, immune. The vaccine delivers surface antigen only, so no core antibody is ever generated. Anti-HBs alone = vaccine response. No treatment needed. Can donate blood.

Susceptible: never infected, never vaccinated. Start HBV vaccine series (3 doses). Counsel on transmission routes. High-risk groups: healthcare workers, dialysis patients, sexual contacts of HBV-positive individuals.

Two possibilities: window period of acute infection (HBsAg cleared, anti-HBs not yet formed) OR old infection with waned anti-HBs. Repeat testing in 4 to 6 weeks. Check HBV DNA if window period is suspected. Do not clear for blood donation.

HEPATITIS A AND C

Which hepatitis virus are you interpreting?

Check anti-HAV antibody class.

Acute HAV infection. Self-limited in most patients. Supportive care. Report to public health. Outbreak investigation if clustering.

Past infection or prior vaccination: immune. No active disease. No treatment needed.

Anti-HCV is the screening test. A positive result means exposure but does NOT confirm active infection.

Active HCV infection confirmed. Treat with direct-acting antivirals (DAA). Preferred regimen: sofosbuvir plus ledipasvir (or velpatasvir depending on genotype). Cure rate above 95%. Check for cirrhosis before choosing regimen length.

Past HCV infection, spontaneously cleared (20 to 30% of patients). No active virus. No treatment needed. Confirm with repeat RNA in 6 months if uncertainty remains.

Practice

Clinical Vignette Quiz

4 questions, randomized each load. Shuffle answer order. Confetti on correct.

Walkthrough

Board-Style Walkthrough

Original board-style vignettes. Shuffled, never-repeat, full explanations for every choice.