Filaria Antibody (IgG4)

Test Code

CPT Codes

Preferred Specimen
0.2 mL serum collected in a red-top tube (no gel)

Minimum Volume
0.1 mL

Transport Container
Plastic screw-cap vial

Transport Temperature
Room temperature

Specimen Stability
Room temperature: 7 days
Refrigerated: 14 days
Frozen: 30 days

Immunoassay (IA)

FDA Status
This test was developed and its analytical performance characteristics have been determined by Quest Diagnostics Infectious Disease. It has not been cleared or approved by FDA. This assay has been validated pursuant to the CLIA regulations and is used for clinical purposes.

Setup Schedule
Set up: Wed; Report available: 1-7 days

Reference Range
<2.50 index

Interpretive Criteria
<2.50 Negative
≥2.50 Positive
This assay detects Filaria IgG4 associated with index infections caused by the major filarial parasites, including Dirofilaria immitis, Wuchereria brancrofti, Brugia malayi, and Onchocerca volvulus. Chronic filarial infections manifesting as elephantiasis may not show a significant IgG4 response and cannot be index ruled out using this test. Samples containing antibodies to other nematodes, particularly Strongyloides, may cross-react in the assay.

Clinical Significance

The filaria IgG4 assay may be helpful in the diagnosis of infections with major filaria parasites, including Wuchereria brancrofti, Brugia malayi, Onchocerca volvulus, and Dirofilaria immitis. Because cross-reactivity may occur in infections with other nematodes, identification of parasites in blood or other body fluid remains the definitive means of diagnosis [2]. A negative result on this test does not rule out chronic filarial infection.

W bancrofti and B malayi cause lymphatic filariasis, a disease transmitted by mosquitoes and characterized by swollen lymph nodes, shaking chills, body aches, fever, and edema in the extremities and genitals [1]. Lymphatic filariasis is common in tropical and subtropical regions of Africa, Asia, and South America. Most cases in the United States are seen among immigrants or visitors from endemic countries and, sometimes, individuals who travel from the United States to endemic countries [1,2].

O volvulus is transmitted to humans through bites of black flies in Africa, Latin America, and the Middle East. The infection mostly affects skin, lymph nodes, and eyes. Severe ocular lesions can lead to blindness known as "river blindness" [2,3].

D immitis, also known as dog heartworms, infects dogs, wild canids, and humans through mosquito bites worldwide, including in North America. Infected humans are usually symptomatic. Occasionally, dying adult worms in pulmonary arteries cause nonspecific symptoms such as coughing, low-grade fever, and chest pain [2,4].

Generally, clinicians order this test when individuals from regions endemic for filariasis present with symptoms consistent with the infection. Early diagnosis of disease at the subclinical level may decrease the risk of complications [1,2].

The results of this test should be interpreted in the context of pertinent clinical and family history and physical examination findings.

1. National Organization of Rare Diseases. Filariasis. Accessed September 21, 2021.
2. Carroll KC, et al. Manual of Clinical Microbiology. 12th ed. ASM Press; 2019. Accessed September 21, 2021.
3. Center for Disease Control and Prevention. Onchocerciasis. Accessed September 21, 2021.
4. Center for Disease Control and Prevention. Dirofilariasis. Accessed September 21, 2021.

Performing Laboratory
Quest Diagnostics Nichols Institute-San Juan Capistrano, CA
33608 Ortega Highway
San Juan Capistrano, CA 92675-2042

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.