DIRECT WET SMEAR: Quality Control (cont.)

4. Protozoan trophozoite cytoplasm should stain pale blue and the nuclei should stain a darker blue with the methylene blue stain. Human WBCs mixed with negative stool should stain the same colors as seen with the protozoa.

5. The microscope should be calibrated (within the last 12 months), and the original optics used for the calibration should be in place on the microscope when objects are measured. Although some feel calibration is not required on a yearly basis, if the microscope receives heavy use, is in a position where it can be bumped, or does not receive routine maintenance, then yearly calibration is recommended. The calibration factors for all objectives should be posted on the microscope or close by for easy access.

6. All QC results should be appropriately recorded; the laboratory should also have an action plan for "out of control'' results.