Ascariasis Serological Test: Diagnosis of Visceral Larva Migrans via ELISA & IHA
Ascariasis Serological Test
Synonyms
Ascaris lumbricoides Serological Test, Toxocara canis Serological Test, VLM (Visceral Larva Migrans) Serological Test
Abstract
The Ascariasis serological test detects antibodies associated with Ascaris lumbricoides, a nematode parasite that inhabits the human small intestine. In some patients, larval migration results in a condition known as Loeffler’s syndrome or Ascaris pneumonitis.
Patient Care/Preparation
Fasting is required before drawing a blood sample for this test.
Specimen
Type: Serum
Container: Red top tube
Storage Instructions
Refrigerate the specimen at 4°C until processing.
Reason to Reject Sample
- Improper labeling
- Excessive hemolysis
- Lipemic serum
- Gross contamination
Special Instructions
The ordering physician must include the patient’s age, sex, occupation, address, clinical symptoms, and date of symptom onset with the specimen submission.
Reference Range
- ELISA: <1:32
- IHA: <1:128
Use
This test aids in the clinical diagnosis of visceral larva migrans, especially in patients with unexplained eosinophilia or pulmonary symptoms consistent with parasitic infection.
Limitations
- Cross-reactivity can cause false positives, particularly with other nematodes like Toxocara.
- IHA tests for VLM are nearly 100% cross-reactive with Ascaris lumbricoides.
- ELISA tests using Ascaris-absorbed antigens offer better specificity.
Methodology
Diagnosis is supported through:
- Enzyme-Linked Immunosorbent Assay (ELISA)
- Indirect Hemagglutination Assay (IHA)
Microscopy of stool specimens may also identify Ascaris ova.
Additional Information
Visceral larva migrans and systemic ascariasis are often associated with notable blood and tissue eosinophilia. A combination of clinical findings and serological testing is essential for accurate diagnosis, especially in endemic regions or patients with travel history to such areas.
References
- Ash LR, Orihel TC, Atlas of Human Parasitology, 3rd ed., ASCP Press, 1990: 134–137.
- Jacobs et al., Laboratory Test Handbook, Lexi-Comp Inc., 1994.
