Overview
The HDV Antibody Test is a blood test used to detect antibodies produced against the Hepatitis D Virus (HDV), also known as the Delta Virus. HDV is a unique, defective virus that cannot survive or replicate on its own. It requires the presence of the Hepatitis B Virus (HBV) to multiply.
This means the HDV infection only occurs in people who are already infected with Hepatitis B. HDV infection can happen at the same time as HBV (co-infection) or develop later (superinfection). Superinfection is more dangerous and leads to faster and more severe liver damage.
The test plays a crucial role in diagnosing past or current HDV infection, especially in individuals who already have Hepatitis B and show signs of worsening liver health.
How HDV Behaves in the Body
HDV does not originate in the human body. When the virus enters the bloodstream, it travels to the liver, where it infects liver cells (hepatocytes). Unlike other viruses, HDV is incomplete and needs a helper virus — HBV — to replicate.
Antibody Production
In response to this infection, the immune system produces HDV antibodies (mainly IgM and IgG). These antibodies are what the HDV test detects.
Role of HBV
- Without HBV, HDV cannot replicate.
- In people with chronic HBV infection, HDV multiplies more aggressively, causing rapid liver damage.
Medical Importance of the HDV Antibody Test
The HDV test has significant medical use, especially for patients already diagnosed with HBV:
✔ Detecting Exposure to HDV
The test identifies whether a person has ever been infected with Hepatitis D.
✔ Differentiating Between HBV-Only Infection and HBV + HDV
Co-infection or superinfection often results in more severe symptoms, elevated liver enzymes, and faster liver deterioration.
✔ Assessing Risk of Complications
Patients with HDV and HBV together have a higher risk of:
- Cirrhosis
- Liver failure
- Hepatocellular carcinoma (liver cancer)
- Rapid disease progression
✔ Guiding Treatment
HDV-positive individuals require specialized antiviral therapy and close follow-up.
Causes of Low or Negative HDV Antibody Levels
A negative HDV antibody result means:
✔ No Exposure
The person has never been infected with HDV.
✔ Early Stage of Infection
Antibodies may not appear immediately, especially in the first few weeks.
✔ Weak Immune Response
People with weak immunity (HIV patients, transplant recipients) may not produce enough antibodies, leading to false-negative results.
Even with a negative HDV test, HBV-related symptoms may still be present.
Symptoms of Low/Negative Levels
There are usually no symptoms linked to low or negative HDV antibodies because there is no infection.
However, if the person has Hepatitis B, they may show:
- Fatigue
- Mild jaundice
- Liver discomfort
These symptoms are due to HBV, not HDV.
Causes of High or Positive HDV Antibody Levels
Positive HDV antibody levels may indicate:
✔ Active Co-Infection
HBV + HDV together, causing sudden or severe liver symptoms.
✔ Superinfection
HDV infection developing in someone already living with chronic HBV.
This is the most dangerous form.
✔ Past Infection
Some antibodies may remain even after the infection has resolved.
✔ Chronic HDV Infection
Long-term infection leading to continuous liver damage.
In most cases, doctors order an HDV RNA test to confirm whether the infection is currently active.
Symptoms When HDV Levels Are High
High HDV antibody levels indicate past or current infection. Symptoms mostly arise from liver inflammation:
- Fatigue
- Weakness
- Loss of appetite
- Jaundice (yellowing of skin and eyes)
- Right upper abdominal pain (liver area)
- Dark urine and pale stools
- Nausea or vomiting
Chronic or Severe HDV Infection Symptoms
- Ascites (fluid buildup in abdomen)
- Easy bruising or bleeding
- Confusion or altered behavior (due to liver failure)
- Swelling in legs
- Severe jaundice
These symptoms indicate advanced liver disease and require urgent care.
Reference Ranges
HDV antibody test results are typically reported as:
✔ Negative
No HDV antibodies detected
→ No HDV infection
✔ Positive
HDV antibodies detected
→ Past or present infection
→ HDV RNA test needed for confirmation of active disease
The HDV RNA test gives a precise measure of viral replication.
Sample Type Used for HDV Testing
The test uses:
- Blood sample (serum)
Collected from a vein in the arm.
Additional tests that may be done along with HDV antibodies:
- HBV markers
- Liver function tests
- HDV RNA testing
- Ultrasound or FibroScan (to assess liver damage)
Test Preparation
- No fasting needed
- Inform your doctor if you are taking antiviral medicines
- If you have HBV symptoms suddenly worsening, testing should be done promptly
- If you recently had a blood transfusion, inform your doctor
When to Consult a Doctor
You should seek medical advice if you have:
- Known Hepatitis B infection
- Sudden worsening of HBV symptoms
- Persistent fatigue
- Yellow eyes or skin
- Dark urine
- Severe abdominal pain
- Swelling in the legs or abdomen
- Symptoms of liver failure
- History of high-risk behavior (unprotected sex, sharing needles)
Doctors may recommend testing if your liver enzymes are unusually high despite HBV treatment.
Important Word Explanations
- HDV (Hepatitis D Virus): A defective virus that needs HBV to survive.
- Co-infection: HBV and HDV acquired together.
- Superinfection: HDV infection occurring after chronic HBV infection.
- Antibodies: Proteins made by the immune system to fight infections.
- HDV RNA Test: A test that detects active viral replication.
- Cirrhosis: Severe liver scarring.
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