False Positive Hepatitis B test Conundrum?

Hepatitis B Panel – Clinical Interpretation

Based on the lab results shown:

1. Hepatitis B surface antigen (HBsAg): NEGATIVE

This means no active hepatitis B infection at the time of testing.

2. Hepatitis B surface antibody (anti-HBs): more than1000 mIU/mL

Reference: more or equal than 12 mIU/mL = immune

A level this high indicates strong immunity to hepatitis B.

This is most commonly due to prior vaccination (or past infection with full recovery).

3. Hepatitis B core antibody IgM (anti-HBc IgM): REACTIVE (S/CO 2.22)

Normally, a positive core IgM suggests acute or recent infection.

However, in this case it is discordant with the other results.

Overall Interpretation (Key Point)

This pattern is NOT consistent with acute hepatitis B infection.

Why:

Acute HBV requires HBsAg positive, which is negative here

Strong surface antibody ( more tahn 1000) argues against active infection

No clinical context suggesting acute hepatitis provided

Most likely explanation

False-positive hepatitis B core IgM, which is known to occur due to:

Assay cross-reactivity

Recent vaccination

Autoimmune conditions

Other viral infections

This is a well-recognized lab phenomenon.

Recommended Next Steps (Standard of Care)

To fully close the loop and document clearly:

Repeat hepatitis B core IgM (confirmatory)

Order hepatitis B core total antibody (anti-HBc total)

Check liver enzymes (AST, ALT) if not already done

HBV DNA PCR only if there is clinical concern or abnormal LFTs

Clinical Bottom Line

✅ No evidence of active hepatitis B

✅ Patient is immune to hepatitis B

⚠️ Isolated positive core IgM is most likely false positive

📌 Document as discordant serology – no active HBV