To examine the coverslip, start at one corner and move systematically through the sample (Figure 10). Focus up and down as you move through the sample, unless you suspect a parasite of particular size. If this is the case, you may concentrate your efforts at the layer in which that parasite is found. Examine the entire coverslip with the 10× objective lens (total magnification 100×). Small parasites or other objects should then be examined with the 40× objective lens (total magnification 400×). Do not use the 100× (oil immersion) objective lens to examine fecal flotation slides. Some laboratories will spot-check five to 10 fields in the center of the slide using 400× magnification to ensure that very small parasites are not overlooked. This certainly is a viable option, although we do not recommend it as a routine procedure in the clinic since questionable small objects will be examined at a higher magnification anyway.

Byron L. Blagburn, MS, PhD
Jamie M. Butler, BS
Department of Pathobiology
College of Veterinary Medicine
Auburn University
Auburn, AL 36849-5519

REFERENCES

2. Dryden MW, Payne PA, Ridley R, et al. Comparison of common fecal flotation techniques for the recovery of parasite eggs and oocysts. Vet Ther 2005;6:15-28.

3. Dryden MW, Payne PA, Smith V. Accurate diagnosis of Giardia spp and proper fecal examination procedures. Vet Ther 2006;7:4-14.

4. Payne PA, Dryden MW. Accurate evaluation of fecal samples critical to patient. DVM Best Practices 2003;Mar:8-11.