CONCENTRATION: Procedure (cont.)

has very little stool in the vial. If the specimen contains a lot of mucus, do not strain through gauze but immediately fix in 5 or 10% formalin for 30 min and centrifuge for 10 min at 500 x g. Then proceed directly to step 10.

3. Add 0.85% NaCl or 5 or 10% formalin (some workers prefer to use formalin for all rinses) almost to the top of the tube and centrifuge for 10 min at 500 x g. The amount of sediment obtained should be approximately 0.5 to 1 ml.

4. Decant the supernatant fluid and resuspend the sediment in saline or formalin; add saline or formalin almost to the top of the tube and centrifuge again for 10 min at 500 x g. This second wash may be eliminated if the supernatant fluid after the first wash is light tan or clear. Some prefer to limit the wash step to one (regardless of