Finding the right tests…
Emergency services available 24 x 7
Emergency services available 24 x 7
Finding the right tests…
Haematology
This test looks for microfilariae, the immature form of the filarial worm, directly under a microscope in a sample of your blood. A lab technician spreads a thick blood film on a slide, stains it, and scans it for the moving, thread-like larvae released by adult worms living in the lymphatic system. Because these larvae circulate in the highest numbers in blood between roughly 10 p.m. and 2 a.m. in most parts of India, the sample is usually collected at night to catch them at their peak. Seeing the parasite directly, rather than a marker of it, is what sets this test apart from a rapid antigen card.
A pathologist reports whether microfilariae were seen on the slide, and if so, roughly how many were present per unit of blood. Because the exact species of filarial worm can sometimes be identified from the shape and staining pattern of the larvae, the report may also note the likely species. Concentration techniques, such as spinning the sample down before examining it, can be used to pick up very low numbers of larvae that a plain smear might miss.
Microfilariae are released by adult filarial worms living in the lymphatic vessels and circulate in blood on a roughly day-night cycle tied to the biting habits of the mosquitoes that transmit the infection. This test was, for decades, the standard way to confirm an active filarial infection, and it still is in many settings.
Microfilariae released by Wuchereria bancrofti and Brugia species peak in the bloodstream at night, generally between 10 p.m. and 2 a.m., in most regions outside the Pacific. A daytime sample can miss larvae that are present but temporarily withdrawn into deeper blood vessels, which is why the centre may ask you to come in, or give a sample, during those hours.
Unlike a rapid antigen card, which only reports presence or absence of a protein signal, examining the actual microfilariae under a microscope can estimate how many are circulating and sometimes identify the species involved. Concentration methods, such as the Knott's technique, are used to improve detection when larvae numbers are low, since a routine thick smear alone can miss a light infection.
This test needs a trained microscopist and takes longer than a card test, which is the trade-off for the more detailed information it provides.
Microfilariae circulate in the highest numbers in blood at night, generally between 10 p.m. and 2 a.m., so a sample taken during that window is more likely to catch them if present.
No. MF BY CARD detects a circulating protein from the adult worm and can be done any time of day. This test looks for the microfilariae themselves under a microscope, which is why timing matters.
A negative smear means microfilariae weren't seen in that sample. A light infection, an unusual sampling time, or early infection can all produce a false negative, so your doctor may repeat testing or use another method.
Often yes. The shape and staining pattern of the microfilariae under the microscope can point to the likely species, which isn't something a rapid antigen card reports.
This page is general information about the test, not medical advice. Your own report's reference ranges apply — please discuss your results with your doctor.
A card test gives a fast presence or absence answer. This microscopy test lets a pathologist see the parasite directly, estimate how many are circulating, and sometimes identify the species, which is useful for confirming or following up an infection.
Ask your doctor or the centre for their exact instructions. Timing and any other preparation can vary between centres.