SOP 5: Modified Knott’s Test

The method is used for the detection of microfilariae in the blood. The method is more sensitive than a direct smear with fresh blood as it concentrates the microfilariae.

Reagents

• 2% formalin
• 1% methylene blue

Procedure

1. Mix 1 ml blood with 9 ml of 2% formalin in a conical centrifuge tube
2. Invert the tube gently 4 times to mix the solution
3. Centrifuge at 500 g for 5 min
4. Discard supernatant
5. Stain sediment for 1-2 min with 1-2 drops of 0.1% methylene blue
6. Add a drop of the sample on a glass slide and cover with a coverslip
7. Examine under a light microscope at low power (10x) for microfilariae

Safety precautions

• Wear lab coat and disposable gloves

Clean up procedures

• Dispose of all slides and cover slips in a sharps container