Points to Ponder for NEET-PG, FMGE & NEXT
- Microscopic examination of blood smears (thick smear, night time collection) is the gold standard for filariasis diagnosis.
- Consider MFC for increased sensitivity in low-burden infections.
- ELISA or rapid tests can be used to detect W. bancrofti infection by identifying circulating filarial antigens.
- Serological tests have limitations and are not the primary diagnostic tool.
Detection of Microfilariae (Mf):
- Microscopic examination of blood smear: This is the gold standard for filariasis diagnosis.
- Nighttime blood collection: Crucial due to the nocturnal periodicity of many filarial species (microfilariae are more abundant in the bloodstream at night).
- Thick smear: Preferred method for microfilariae detection due to increased sensitivity compared to thin smears.
- Membrane filtration concentration (MFC): Most sensitive method for detecting low parasite burdens. It concentrates microfilariae from a larger blood volume, but requires specialized equipment.
Other Diagnostic Methods:
- Circulating filarial antigen detection:
- ELISA (enzyme-linked immunosorbent assay): Useful for detecting Wuchereria bancrofti infection, especially when microfilariae are absent (e.g., amicrofilariae).
- Immunochromatographic card tests: Rapid point-of-care tests for W. bancrofti antigen detection.
- Imaging:
- Ultrasonography: May visualize adult worms in dilated lymphatics in some cases.
- Molecular diagnostics:
- PCR (polymerase chain reaction): Detects filarial DNA in blood, but not routinely used due to limited availability and cost.
Serological Tests:
- Detect antibodies against microfilariae or adult worms.
- Limited usefulness due to:
- Cross-reactivity with other helminthic infections.
- Presence of antibodies may not indicate active infection (can persist after successful treatment).
