Ova and Parasite (O&P) Examinations

Introduction | Macroscopic | Microscopic |

Microscopic Examination - Ova and Parasite Examination

Introduction | Direct Wet Smear | Concentration | Permanent Stained Smear

Direct Wet Smear

Quality Control

Check the working iodine solution each time it is used or periodically (once a week). The iodine solution should be free of any signs of bacterial or fungal contamination.
The color of the iodine should be that of strong tea (discard if it is too light).
Protozoan cysts stained with iodine should contain yellow-gold cytoplasm, brown glycogen material, and paler refractile nuclei. The chromatoidal bodies may not be as clearly visible as they were in a saline mount. Human white blood cells (buffy coat cells) mixed with negative stool can be used as a quality control (QC) specimen. The human cells when mixed with negative stool can be used as a quality control specimen. The human cells will stain with the same color as that seen in the protozoa.
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.
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.
All QC results should be appropriately recorded; the laboratory should also have an action plan for "out of control" results.