🧫 Hantaan Virus Antibody Test (IgM/IgG): Complete Guide

Purpose, ICA/IFA Methods, Reference Ranges, Clinical Significance & Interpretation

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📝 Description

Learn everything about the Hantaan virus antibody (IgM/IgG) test, including its purpose, ICA/IFA methods, reference ranges, clinical significance, interpretation tips, and key diagnostic considerations for HFRS.

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🧪 Hantaan Virus (Hantavirus) Antibody Test: Complete Guide

The Hantaan virus, a major species of Hantavirus, is the primary pathogen responsible for Hemorrhagic Fever with Renal Syndrome (HFRS) in Korea.
It is transmitted mainly through exposure to field mice (Apodemus agrarius), and cases occur sporadically every year.

The Hantaan virus IgM/IgG antibody test is essential for diagnosing acute or past infection by evaluating serologic changes across the disease course.

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1. Purpose of the Hantaan Virus Antibody Test

✔ Diagnosing Hemorrhagic Fever with Renal Syndrome (HFRS)

✔ Detecting acute infection (IgM)

✔ Determining past or resolving infection (IgG)

✔ Supporting confirmatory diagnosis with IFA or PRNT

✔ Differentiating causes of fever, thrombocytopenia, or acute kidney injury

HFRS progresses through five phases (Febrile → Hypotensive → Oliguric → Diuretic → Convalescent), making clinical symptoms + antibody dynamics crucial for diagnosis.

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2. Test Methods

🔬 1) ICA (Immunochromatographic Assay)

A rapid lateral-flow type assay widely used as an initial screening test.

Characteristics

• Mainly detects IgM
• Results available in 10–15 minutes
• Can be used as a POCT (point-of-care test)
• Useful for early screening

Advantages

✔ Fast and convenient
✔ Reasonably high sensitivity and specificity

Limitations

✖ Weak-positive results can be difficult to interpret
✖ False negatives may occur during early phase (days 1–4)

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🔬 2) IFA (Indirect Fluorescent Antibody Test)

Considered the reference confirmatory method for Hantaan virus serology.

Principle

1. Viral antigen is fixed on a slide
2. Patient serum is applied
3. Fluorescent-labeled anti-human IgG/IgM binds
4. Fluorescence is visualized under a microscope

Advantages

✔ Very high sensitivity & specificity
✔ Evaluates IgM and IgG simultaneously
✔ Detects fourfold rise between acute and convalescent samples

Limitations

✖ Requires expensive equipment
✖ Requires trained personnel
✖ Subjective interpretation differences may exist

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3. Reference Ranges

Antibody	Normal (Negative)	Positive Criteria
IgM	Negative	Reactive or borderline + compatible symptoms
IgG	Negative	Fourfold rise between acute and convalescent samples

⚠ Cut-off values vary by laboratory.
⚠ Isolated IgM positivity requires confirmation with IFA.

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4. Clinical Significance

🧩 1) IgM Positive

• Indicates recent or acute infection
• Consistent with fever, back pain, abdominal pain, conjunctival injection
• ICA-positive results should be confirmed with IFA

🧩 2) IgG Positive

• Indicates past infection or convalescent phase
• Not a marker of active infection unless:
  → IgG shows a fourfold rise between paired samples

🧩 3) IgM(-) / IgG(-)

• No infection
• Or too early (window period)
  → Re-test in 3–5 days if clinically suspected

🧩 4) IgM(+) / IgG(+)

• Late acute phase or early convalescent stage
• IgM may persist for 2–3 months

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5. Important Interpretation Considerations

✔ 1) Early phase (Days 1–4): Antibodies may be absent

→ High false-negative risk → Repeat testing recommended

✔ 2) Vaccination history

Hantavirus vaccination may produce IgG positivity

✔ 3) Cross-reactivity

Other hantaviruses (e.g., Seoul virus, Soochong virus) may cause mild cross-reactions

✔ 4) Immunocompromised or renal failure patients

Slower antibody response → delayed positivity

✔ 5) IFA interpretation variability

Requires experienced laboratory personnel

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6. Diagnostic Algorithm (Simplified)

1. ICA IgM screening
   → If positive → Proceed to IFA
2. IFA IgM/IgG assessment
3. Fourfold rise in IgG = Confirmed infection
4. Combine with:
   • Clinical symptoms
   • CBC (platelets)
   • Serum creatinine
   • Urinalysis (proteinuria)

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7. Conclusion

The Hantaan virus antibody test is a key diagnostic tool for HFRS.

• ICA is ideal for rapid screening
• IFA provides the most reliable confirmation

Accurate diagnosis requires integrating:
✔ Antibody kinetics
✔ Clinical symptoms
✔ Kidney function
✔ Hematologic changes

This combined approach ensures the highest diagnostic accuracy.

Helicobacter pylori Ag / IgG / IgM Tests

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8. References

• CDC. Hantavirus Clinical Overview.
• Korean Society for Laboratory Medicine. Guidelines for Infectious Serology Testing.
• Lednicky JA. Hantaviruses: Overview and Update. Clin Lab Med.
• Krüger DH et al. Hantavirus infections: Clinical course and diagnosis. Lancet Infect Dis.
• Park KS et al. Epidemiology of Hantavirus in Korea.