To detect trematode eggs in a fecal sample, which method is most appropriate?

• A. Flotation
• B. Sedimentation
• C. Antigen testing
• D. Direct microscopy without processing

Answer: (B)

When looking for trematode eggs in feces, you want a method that actually concentrates the heavier eggs rather than relying on them to float. Flotation relies on buoyancy, and trematode eggs are often too dense to reliably rise to the surface, so they can be missed. Sedimentation uses gravity to pull these dense eggs down into a sediment, which you then examine under the microscope where they’re easier to spot. In practice, a formalin-ethyl acetate or similar sedimentation technique helps remove much of the debris and concentrates the eggs for better detection. Direct microscopy without any processing tends to be less sensitive because debris obscures eggs, and antigen testing detects parasite components rather than the eggs themselves.