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What type of preparation is used to enhance the detail of protozoan cysts?
What is the purpose of using Lugol's iodine or D'Antoni's formula in direct iodine wet preparation?
What is the characteristic of mucus in a diarrheic stool?
What is the purpose of concentration methods in parasitology?
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What is the size of the coverslip used in direct saline wet preparation?
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What type of stool is characterized by scanty mucus?
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What is the amount of stool used in concentration methods?
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What is the objective of concentration methods in parasitology?
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What is the significance of the brown color of stool?
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Which of the following is a disadvantage of using Modified Polyvinyl Alcohol (MPVA) in concentration methods?
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What is the purpose of adding copper sulfate or zinc sulfate to Modified Polyvinyl Alcohol (MPVA)?
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What is a disadvantage of using Schaudinn's fixative (SF) in stool examination?
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Which of the following is a characteristic of Schaudinn's fixative (SF)?
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What is the limitation of using Modified Polyvinyl Alcohol (MPVA) in permanent stained smears?
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What is the primary purpose of using Novy-MacNeal-Nicolle (NNN) medium?
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What is the correct way to report the results of a parasite detection test?
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What type of staining is used for testing CSF?
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What is the purpose of examining 10 fields in a sample?
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What type of fluids are examined for parasite detection?
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Why is proper specimen selection and processing crucial in parasite detection?
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What is the significance of a positive test result in parasite detection?
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Do bacteria need to be reported in parasite detection?
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What is the purpose of centrifuging the specimen with zinc sulfate?
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What is a disadvantage of using zinc sulfate in stool examination?
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What is the purpose of using gauze in the procedure?
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What is the purpose of permanent staining in parasitology?
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What is the purpose of centrifugation in the procedure?
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What is the advantage of using zinc sulfate in stool examination?
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What is the minimum number of fields that must be reviewed before the slide can be considered negative?
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What is the purpose of using iodine solution in the procedure?
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What is the primary purpose of the Kato Katz technique in areas with moderate to high transmission rates?
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What is the limitation of the Kato Katz technique in detecting parasitic infections?
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What is the purpose of using a plastic spatula in the Kato Katz technique?
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What is the purpose of applying a glycerol-soaked cellophane strip to the fecal sample on the microscope slide?
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In what type of surveys is the Kato Katz technique commonly used?
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What is the advantage of using the Kato Katz technique in epidemiological surveys?
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What is the purpose of transferring a small amount of sieved fecal material to the hole of the template?
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What is the recommended practice when removing the template from the microscope slide?
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Study Notes
Stool Examination
- Stool color is important in indicating the condition: brown is normal due to bilirubin, a byproduct of heme in hemoglobin.
Modified Polyvinyl Alcohol (MPVA)
- Alternative to mercury-based PVA
- Contains copper sulfate or zinc sulfate
- Used in concentration methods and permanent stained smears
- Disadvantages:
- Does not provide the same quality of preservation for adequate protozoan morphology on a permanent stained slide as mercury-based fixatives
- Parasite identification is difficult
- More likely negatively affected if proper protocol is not followed
Schaudinn's Fixative (SF)
- Preserves morphologic protozoan, trophozoite, and cysts
- Easy to prepare for permanent staining
- Disadvantages:
- Less suitable for concentration technique
- Contains mercury chloride
- Inadequate preservation of helminth eggs, larvae, coccidian, and microsporidia
Stool Preparation and Examination
- Direct iodine wet preparation: enhances detail of protozoan cysts
- Direct saline wet preparation: enhances detail of protozoa
- Concentration method: uses 2.5g of stool, purpose is to aggregate parasites and remove small debris
- Novy-MacNeal-Nicolle (NNN) medium: used for the recovery of Leshamania spp.
Reporting of Results
- Should state scientific name (genus and species)
- Ex: Entamoeba histolytica cyst seen
Additional Infos
- Is bacteria need to be reported? No, but it depends on the protocol
- In general, most parasites are not quantified; amoeba-presence or absence is reported
Specimen Processing and Laboratory Testing
- Proper specimen selection and processing are crucial to parasite recovery
- When zinc sulfate is added to the specimen and centrifuged, the parasites float to the surface and can be skimmed from the top of the tube
- Advantage: more fecal debris is removed, making it easier for microscopic examination
- Disadvantage: some helminth eggs are very dense and will not float, thus, some parasites will be missed
Materials Needed
- Gauze
- Conical centrifuge tube (15mL)
- Normal saline solution (0.85% / 10% formalin)
- Centrifuge
- Zinc sulfate solution
- Disposable Pasteur pipette/bent wire loop/
- Slides and coverslip
- Iodine solution
- Stool sample
Procedure
- Strain the specimen through a filter containing a single-layer thickness of gauze into a conical tube
- Fill the tube with saline or 10% formalin and centrifuge for 10 minutes at 500 x G (1500rpm)
- Decant the supernatant and repeat if necessary
Permanent Stain
- The use of stained slide preparation provides a permanent record of a patient's specimen and allows review by a consultant
- Permanent stain is designed for analysis using the oil immersion objective (100x)
- 300 fields must be reviewed before the slide can be considered negative
- Designed to detect protozoan cyst and trophozoites
- Staining allows to observe detailed features of protozoa by making its intracellular organelles visible
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Description
This quiz covers the laboratory techniques used in medical parasitology, including the use of Modified Polyvinyl Alcohol (MPVA) and the importance of stool color in diagnosis. It also touches on concentration methods and permanent stained smears.