CONCENTRATION: Procedure

1. Transfer 1/2 teaspoon (about 4 g) of fresh stool into 10 ml of 5 or 10% formalin in a round-bottom tube (container may be modified to suit individual laboratory preferences). Mix the stool and formalin thoroughly and let the mixture stand for a minimum of 30 min for fixation. If the specimen is already in 5 or 10% formalin (or SAF), restir the stool-formalin mixture.

2. Depending on the amount and viscosity of the specimen, strain a sufficient quantity through wet gauze (no more than two layers of gauze and one layer if the new "pressed'' gauze [e.g., Johnson & Johnson nonsterile three-ply gauze, product no. 7636] is used) into a conical 15-ml centrifuge tube to give the desired amount of sediment (0.5 to 1 ml) in step 3 below. Usually 8 ml of the stool-formalin mixture prepared in step 1 will be sufficient. If the specimen is received in vials of preservative (5 or 10% formalin or SAF), then approximately 3 to 4 ml will be sufficient unless the specimen