What this test measures
The filaria antigen rapid test (also called Filariasis ICT — immunochromatographic test, or FTS — Filariasis Test Strip) detects circulating filarial antigen from Wuchereria bancrofti — the parasite responsible for over 90% of lymphatic filariasis in India.
The test uses a drop of fingerprick blood or serum and is read in 10–15 minutes. Unlike the older microfilariae night-blood-smear method, the antigen test does not require night sampling (when microfilariae traditionally circulate) — it can be done any time of day.
Why it matters
Lymphatic filariasis is endemic in many Indian states including Uttar Pradesh, Bihar, Odisha, Andhra Pradesh, Kerala, Tamil Nadu, and parts of Maharashtra. India runs the National Programme for Elimination of Lymphatic Filariasis (ELF) with mass drug administration (DEC + albendazole, sometimes ivermectin) in endemic districts.
The filaria antigen rapid test is the WHO and NCDC-endorsed point-of-care diagnostic — used for individual diagnosis (chronic lymphoedema, hydrocele, acute filarial fever), for transmission assessment surveys (TAS) to evaluate programme success, and for outbreak investigation. A positive antigen confirms active or recent infection regardless of microfilariae presence.
How to prepare
No fasting required. The test uses fingerprick blood or serum and can be done at any time of day (unlike traditional microfilariae smears, which need night blood).
Markers & reference ranges
Reference ranges below are typical adult values. Your lab's reported range may differ slightly based on the assay platform and patient demographics — always read your report against the range printed on it.
| Marker | Normal range | If low | If high |
|---|---|---|---|
| Wuchereria bancrofti Antigen (Reactive / Non-reactive)[1][2] | Non-reactive (Negative) | Non-reactive — no circulating W. bancrofti antigen. In endemic areas with chronic lymphoedema or hydrocele, antigen can be negative years after infection — clinical and ultrasound assessment continue. | Reactive — active or recent W. bancrofti infection. Treatment with DEC (diethylcarbamazine) + albendazole or ivermectin per programme guidelines. Lymphoedema and hydrocele management as needed. |
Filariasis tests — comparison
| Test | What it detects | Sample time | Use case |
|---|---|---|---|
| Antigen Rapid (ICT/FTS) | Circulating W. bancrofti antigen | Any time | WHO-preferred POC test |
| Night blood smear | Microfilariae | Night (10pm–2am) | Traditional method |
| Filaria PCR | Parasite DNA | Any time | Research, complex cases |
| Anti-filarial antibody | IgG/IgM against filaria | Any time | Past exposure (less specific) |
| Ultrasound (scrotal) | Adult worm motion ("filaria dance sign") | Any time | Clinical confirmation |
Frequently asked questions
How is filaria antigen test different from microfilariae smear?
The antigen test detects parasite protein circulating in blood and can be done at any time of day. The traditional microfilariae smear requires night blood (when microfilariae circulate) and is less sensitive. The antigen test is the WHO-preferred modern method.
Can a positive antigen mean past infection?
The antigen typically clears within 1–2 years of effective treatment. Persistently positive antigen in someone with chronic lymphoedema usually indicates ongoing infection.
I have a hydrocele but the antigen is negative. Is it not filaria?
In long-standing chronic disease, the antigen can be negative even when filaria caused the original damage. Ultrasound (looking for adult worm motion or "filaria dance sign") and clinical history help.
Is treatment effective?
Single-dose DEC + albendazole (or DEC + albendazole + ivermectin) kills microfilariae and most adult worms. Chronic lymphoedema and hydrocele require additional surgical or supportive management.
How is filaria spread?
Through mosquito bites (Culex in India). The mosquito picks up microfilariae from infected blood and transmits them to the next person. Vector control matters alongside mass drug administration.
Should family members be tested?
In endemic areas with index cases, family/contact testing is sometimes useful. Mass drug administration in endemic districts covers most household-level risk.
Is the test affordable?
Yes. WHO-prequalified rapid antigen kits are available at low cost, used widely by NCDC programmes and many NABL labs.
Related Infectious Disease tests
Tests commonly ordered alongside FILARIA ANTIGEN RAPID TEST, or that help interpret an unexpected result.
Sources & references
- NCDC India — Elimination of Lymphatic Filariasis · accessed 2026-05-30T00:00:00.000Z
- WHO — Lymphatic Filariasis · accessed 2026-05-30T00:00:00.000Z
- CDC — Lymphatic Filariasis · accessed 2026-05-30T00:00:00.000Z
- ICMR India — Filariasis Surveillance · accessed 2026-05-30T00:00:00.000Z
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