PROFICIENCY TESTING

Wet Preparations

How should you examine a wet preparation for proficiency testing?

Most directions will recommend you shake the vial and take a sample from the mixed vial contents.  However, if the number of eggs is few, you may be better off taking a very small drop from the settled material. If you take too large a drop, it will be too thick to examine properly.  Make sure you do not add too much iodine; very darkly stained helminth eggs can resemble debris.

Are there any “tips” regarding the microscope set up for the examination of an unstained wet preparation?

The microscope should be aligned properly using Köhler illumination.  Make sure the light is not too bright; otherwise, you may shine right through the organisms and miss the parasites.  Also, you may want to close the diaphragm a bit to provide a bit more contrast.  Extra contrast is particularly important when reading with saline only (no iodine added).

Permanent Stained Smears

How should you examine a permanent stained fecal smear for proficiency testing?

Make sure the light is very bright (condenser all the way up) and the diaphragm is open.  Review both thin and thick areas of the smear; examine at least 300 oil immersion fields (using the 100X oil immersion objective) before you report the specimen as a negative.  If you use the 50X or 60X scanning oil immersion lens, you still need to review 300 oil fields as indicated above.