What rpm and time are specified for centrifugation in Modified Knott's technique?

• A. 1000 rpm for 3 min
• B. 2000 rpm for 7 min
• C. 1500 rpm for 5 min
• D. 1200 rpm for 4 min

Answer: (C)

Central concept: centrifugation during the Modified Knott's technique is used to concentrate microfilariae by pulling them into a sedimented pellet after the red blood cells have been lysed. The specified setting of 1500 rpm for 5 minutes is chosen because it provides enough force to collect the microfilariae into a compact pellet without damaging them or pulling in excessive debris. This makes it easier to visualize and identify the organisms under the microscope after staining. If the speed were much higher or the time longer, you risk damaging the microfilariae or creating a pellet full of debris; if it were lower or shorter, the microfilariae might not pellet well and could be missed.