Since lymphatic filariasis does not always result in clinical symptoms, the most accurate way to determine if someone is infected is a blood test. In most parts of the world, the parasites have a "nocturnal periodicity" that restricts their appearance in the blood to only the hours of 10pm - 2am. Therefore, the diagnosis of lymphatic filariasis traditionally has depended on the laboratory examination of blood taken between 10pm and 2am when microfilaria are most common in peripheral blood. Besides "night blood films" blood taken at night can be tested by filtration or concentration techniques which are more sensitive as more blood can be taken.
However, an antigen-detection test that is simple, sensitive and specific, called an ICT (see graphic below), is now available. The ICT test can detect infection within minutes and -unlike previous tests - can be carried out at any time of day.
The simplicity of using ICT cards for LF detection is demonstrated in these pictures. The left ICT card displays negative results for LF infection, while the right card displays positive results