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Filariasis IgG/IgM Rapid Test Cassette
The Filariasis IgG/IgM Rapid Test is a lateral flow immunoassay for the simultaneous detection and
differentiation of IgG and IgM anti‐lymphatic filarial parasites (W. Bancrofti and B. Malayi) in human
serum, plasma or whole blood. This test is intended to be used as a screening test and as an aid in
the diagnosis of infection with lymphatic filarial parasites. Any reactive specimen with the
Filariasis IgG/IgM Rapid Test must be confirmed with alternative testing method(s).
SUMMARY AND EXPLANATION OF THE TEST
The lymphatic filariasis known as Elephantiasis, mainly caused by W. bancrofti and B. malayi, affects
about 120 million people over 80 countries1,2. The disease is transmitted to humans by the bites of
infected mosquitoes within which the microflariae sucked from an infected human subject develops
into third‐stage larvae. Generally, repeated and prolonged exposure to infected larvae is required
for establishment of human infection.
The definitive parasitologic diagnosis is the demonstration of microflariae in blood samples3.
However, this gold standard test is restricted by the requirement for nocturnal blood collection and
lack of adequate sensitivity. Detection of circulating antigens is commercially available. Its
usefulness is limited for W. bancrofti4. In addition, microfilaremia and antigenemia develop from
months to years after exposure.
Antibody detection provides an early means to detect filarial parasite infection. Presence of IgM to
the parasite antigens suggest current infection, whereas, IgG corresponds to late stage of infection
or past infection5. Furthermore, identification of conserved antigens allows ‘pan‐filaria’ test to be
applicable. Utilization of recombinant proteins eliminates cross‐reaction with individuals having
other parasitic diseases6. The Filariasis IgG/IgM Rapid Test uses conserved recombinant antigens
to simultaneously detect IgG and IgM to the W. bancrofti and B. malayi parasites without the
restriction on specimen collection.
TEST PRINCIPLEThe Filariasis IgG/IgM Rapid Test is a lateral flow chromatographic immunoassay. The test cassette
consists of: 1) a burgundy colored conjugate pad containing recombinant W. bancrofti and B. malayi
common antigens conjugated with colloid gold (Filariasis conjugates) and rabbit IgG‐gold
conjugates, 2) a nitrocellulose membrane strip containing two test bands (T1 and T2 bands) and a
control band (C band). The T1 band is pre‐coated with monoclonal anti‐human IgM for the
detection of IgM anti‐ W. bancrofti and B. malayi, T2 band is pre‐coated with reagents for the
detection of IgG anti‐W. bancrofti and B. malayi, and the C band is pre‐coated with goat anti rabbit
When an adequate volume of test specimen is dispensed into the sample well of the cassette, the
specimen migrates by capillary action across the cassette. W. bancrofti or B. malayi IgM antibodies
if present in the specimen will bind to the Filariasis conjugates. The immunocomplex is then
captured on the membrane by the pre‐coated anti‐human IgM antibody, forming a burgundy
colored T2 band, indicating a W. bancrofti or B. malayi IgM positive test result.
W. bancrofti or B. malayi IgG antibodies if present in the specimen will bind to the Filariasis
conjugates. The immunocomplex is then captured by the pre‐coated reagents on the membrane,
forming a burgundy colored T1 band, indicating a W. bancrofti or B. malayi IgG positive test result.
Absence of any test bands (T1 and T2) suggests a negative result. The test contains an internal
control (C band) which should exhibit a burgundy colored band of the immunocomplex of goat anti
rabbit IgG/rabbit IgG‐gold conjugate regardless of the color development on any of the test bands.
Otherwise, the test result is invalid and the specimen must be retested with another device.
Contact Person: Ms. Anna Lee