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Questions and Answers
What is a limitation of identifying protozoan parasites through microscopic examination?
What is a limitation of identifying protozoan parasites through microscopic examination?
Which of the following is NOT mentioned as a factor to consider in the history of a suspected parasitic infection?
Which of the following is NOT mentioned as a factor to consider in the history of a suspected parasitic infection?
Why should specimens not be collected in diapers?
Why should specimens not be collected in diapers?
What type of stool consistency is specifically mentioned for examining liquid and soft stool?
What type of stool consistency is specifically mentioned for examining liquid and soft stool?
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What should NOT be present in a stool sample container?
What should NOT be present in a stool sample container?
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What is the maximum time frame for examining liquid or soft stool after collection?
What is the maximum time frame for examining liquid or soft stool after collection?
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Which of the following products should be discontinued three days prior to stool analysis?
Which of the following products should be discontinued three days prior to stool analysis?
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What is the recommended action if a stool specimen is preserved?
What is the recommended action if a stool specimen is preserved?
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What is the primary disadvantage of the flotation method for parasite recovery?
What is the primary disadvantage of the flotation method for parasite recovery?
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In the context of stool examination, what is a significant challenge when using permanent stained smears?
In the context of stool examination, what is a significant challenge when using permanent stained smears?
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What does the Kato-Katz technique primarily quantify?
What does the Kato-Katz technique primarily quantify?
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Which technique is based on the active migration of larvae for identification?
Which technique is based on the active migration of larvae for identification?
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Which parasite types are NOT typically identified using stool examination techniques discussed?
Which parasite types are NOT typically identified using stool examination techniques discussed?
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Why are permanent stained smears typically used in stool examination?
Why are permanent stained smears typically used in stool examination?
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What is a common limitation of sedimentation procedures compared to flotation methods?
What is a common limitation of sedimentation procedures compared to flotation methods?
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How is the egg count typically expressed when using the Kato-Katz technique?
How is the egg count typically expressed when using the Kato-Katz technique?
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Which procedure provides the quickest answer for detecting motility of trophozoites?
Which procedure provides the quickest answer for detecting motility of trophozoites?
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What is the purpose of using methylene blue in a staining saline preparation?
What is the purpose of using methylene blue in a staining saline preparation?
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What enhancement does adding formalin and ethyl acetate to sedimentation methods provide?
What enhancement does adding formalin and ethyl acetate to sedimentation methods provide?
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In the wet mount technique, what is observed to detect motile organisms?
In the wet mount technique, what is observed to detect motile organisms?
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Which method is primarily used when results from the direct smear need to be confirmed?
Which method is primarily used when results from the direct smear need to be confirmed?
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What is a primary benefit of using centrifugation in the sedimentation method?
What is a primary benefit of using centrifugation in the sedimentation method?
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What effect does eosin solution have in a saline preparation?
What effect does eosin solution have in a saline preparation?
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What is a limitation of the direct smear method in microscopy?
What is a limitation of the direct smear method in microscopy?
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Which method is known for its specificity and ability to detect active infections in early stages?
Which method is known for its specificity and ability to detect active infections in early stages?
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What is the primary use of DNA probes in molecular biological techniques?
What is the primary use of DNA probes in molecular biological techniques?
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Which of the following methods allows for the distinction between morphologically similar organisms?
Which of the following methods allows for the distinction between morphologically similar organisms?
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What characteristic of antibodies poses a potential challenge in serological testing?
What characteristic of antibodies poses a potential challenge in serological testing?
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Which feature of latex agglutination tests increases their reliability?
Which feature of latex agglutination tests increases their reliability?
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What is a downside of using filter paper culture for nematode larvae?
What is a downside of using filter paper culture for nematode larvae?
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Which of the following statements about antigen detection methods is true?
Which of the following statements about antigen detection methods is true?
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Which of the following components is commonly used to label DNA probes for detection purposes?
Which of the following components is commonly used to label DNA probes for detection purposes?
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Study Notes
Laboratory Diagnosis of Parasitic Infections
- Failure to identify a parasite does not rule out the possibility of infection.
- Many protozoa are only identifiable through microscopic examination.
- Microscopic examination requires significant expertise and is time-consuming and has limitations
- Direct methods include urine, stool, sputum, biopsy, and blood examinations.
- Indirect methods include IHA (Indirect hemagglutination) tests, latex agglutination, immunofluorescence assays, and ELISA.
- Molecular methods include PCR and DNA probes.
Stool Sample Collection
- Samples should be collected in clean, dry, screw-top containers.
- Label samples with patient details (name, birthdate, date).
- Avoid contamination with urine, disinfectants, or soap as these can destroy amoebae.
- Samples in diapers are not acceptable.
- Samples should be fresh.
- Analyze liquid and soft stools within 15 minutes; other stool types within 3 days.
- Avoid antacids and other medicines as these can affect results.
Stool Examination
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Macroscopic Examination: Evaluates stool consistency, colour, and composition.
- Consistency: Categorized using Bristol Stool Scale (types 1-7).
- Color: Variations like brown, bright red, pale yellow, white, or green.
- Composition: presence of mucus, blood, undigested food, etc.
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Microscopic Examination: Permanent and temporary staining techniques.
- Examples: Direct saline smear, Iodine smear, concentration techniques (flotation, sedimentation), various stains for specific parasites. This step analyzes the microscopic components of the sample.
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Additional tests: Include culture, cellophane tape test, Baermann technique, Ova quantification (Stoll & Kato). These tests are used depending on the suspected or detected species.
Stool Examination - Additional Notes
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Concentration Techniques: Used to increase the detection of parasites in cases of low infestation. This is followed by microscopic analysis.
- Sedimentation, Flotation (using different solutions e.g., zinc sulphate, Sheather's sugar).
- For concentrating parasites and removing background debris enhancing visibility of parasites.
- Staining: Staining techniques like direct saline smear, iodine smear allow visualisation of parasites. These techniques aid in proper identification. Permanent staining methods (e.g., iron haematoxylin, trichrome, Giemsa, modified Ziehl-Neelsen, modified Safranin) used in cases where organisms need specific staining
- Other Methods: Include culture, cellophane techniques (Baermann), and various techniques for ova quantification.
Stool Examination - Specific Techniques
- Sedimentation: Separates heavier components (parasites) in the stool from lighter materials.
- Flotation: Utilizes different solutions of varying densities to separate parasites from the stool based on their buoyancy. Parasites heavier than the solution will sink.
- Wet Mounts: Wet preparations such as saline and iodine are simple to prepare and immediately visualize motility.
Stool Examination - Additional Notes
- Negative Results: Confirmation of negative results may need concentration methods or permanent stains.
- Specific Tests: These depend on the suspected type of infection.
Other tests
- Molecular Technique: PCR, and DNA probes.
- Immunological methods: used to detect antigens and antibodies. They are a faster method to detect active infections.
- Staining-relevant information/methodologies: Iron haematoxylin, trichrome, giemsa, modified Ziehl-Neelsen, modified Safranin technique
- Diagnostic Methodology for Specific Parasites: Information varies by the parasite suspected. This needs additional specific information.
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Description
This quiz covers the procedures and techniques used in the laboratory diagnosis of parasitic infections. It includes both direct and indirect methods of testing, as well as guidelines for stool sample collection. Test your knowledge on the best practices for identifying parasites and the limitations of various diagnostic methods.
