38 Questions
What is the primary purpose of concentration methods in parasitology?
To detect small numbers of parasites that might not be detected using direct preparations
What is the principle of the Formalin-Ethyl Acetate Sedimentation Procedure?
Parasites are heavier than the solution
What type of sample is typically used for staining in concentration methods?
PVA preserved sample
What is the main advantage of Trichrome stain?
It has a long shelf life and easy procedure
What is the advantage of using concentration methods over direct preparations?
It enables the detection of small numbers of parasites
Which of the following parasites can be detected using concentration methods?
Protozoan cysts, oocysts, helminth eggs, and larvae
What is the purpose of reviewing 300 fields in sediment techniques?
To ensure the slide is considered negative
What is the main difference between sedimentation and flotation techniques?
In sedimentation, parasites are heavier than the solution, while in flotation, they are less dense
What is the purpose of centrifugation in concentration methods?
To separate parasites from fecal debris
What is the limitation of using SAF fixed specimens for staining?
Staining is limited to iron-hematoxylin only
What is the purpose of using a commercial antibody in stool screening methods?
To detect antigen in the patient's specimen
What type of parasites are detected using Acid fast stain?
Oocysts of Cryptosporidium, Isospora, and Cyclospora
What is the advantage of preparing slides from fresh stool specimens?
It allows for the immediate fixation of the sample
What is the purpose of sealing the slides with a permanent mounting sealant after staining?
To preserve the slides for future reference
What is the advantage of Iron hematoxylin stain?
It reveals excellent morphology of the intestinal protozoa
What is the purpose of centrifugation in sedimentation techniques?
To concentrate the parasites in the sediment of the tube
What is a potential health risk associated with PVA preserved specimens?
Exposure to mercuric chloride
What is a characteristic of stool that may suggest the presence of protozoan trophozoite?
Soft or liquid stool
What is the main advantage of using Sodium Acetate Formalin (SAF) over PVA?
SAF is free of formalin and mercury
What is the primary purpose of macroscopic analysis of stool?
To examine the stool for gross abnormalities
What is the significance of stool consistency in parasite detection?
Stool consistency serves as an indication of potential parasite presence
What is the main advantage of the Alternative Single-Vial System?
It is free of formalin and mercury
What is the purpose of microscopic analysis of stool?
To detect the presence of parasites in stool
What is a characteristic of formed stool?
It is hard or formed
What is the significance of the color of stool in parasite detection?
It indicates the patient's condition or status
What is a disadvantage of PVA preserved specimens?
Difficult disposal of the specimens
What is the purpose of the modified trichrome stain in parasitic infections?
To detect spores of microsporidia
What is the primary advantage of antigen detection methods?
They are highly sensitive and specific for certain parasites
What is the limitation of examining stool specimens in parasitic infections?
It may not detect the infectious agent in certain parasitic infections
What is the purpose of using other intestinal specimens in parasitic infections?
To detect parasites that are not present in stool specimens
What is the characteristic of rapid test or stool screening methods?
They are highly sensitive and specific
Which of the following is NOT an assay method for detecting parasitic infections?
Polymerase Chain Reaction
What type of parasites can be isolated with culture?
E. histolytica, T. vaginalis, Leishmania spp.
What is the primary advantage of antigen detection over antibody detection?
It is more reliable and indicative of current infection.
What type of laboratories offer immunologic testing?
Specialized laboratories and research facilities.
What information should be included in the report of a positive specimen?
The scientific name and stage of the parasite.
How should the presence of blood cells be reported in a specimen?
Semi-quantitatively, as rare, few, moderate, or many.
What is the primary reason why immunologic testing is not usually performed in routine laboratories?
The tests require specialized expertise.
Study Notes
Concentration Method
- A microscope slide with a fixed sample that has been allowed to dry and subsequently stained is used to detect small numbers of parasites that might not be detected using direct preparations.
- The purpose of concentration is to aggregate the parasites present into a small volume of sample and remove as much debris as possible.
- Concentration techniques can be performed on fresh or preserved specimens and enable the detection of protozoan cyst, oocyst, helminth eggs, and larvae.
Advantages and Disadvantages
- Advantages: enables detection of small numbers of parasites, allows for detailed observation of protozoa by staining intracellular organelles, and is a viable alternative to the use of PVA and Schaundinn fixative.
- Disadvantages: PVA that contains Schaundinn solution contains mercuric chloride, which can lead to potential health problems, and the disposal of such fixatives can be difficult.
Single-Vial System
- An alternative to PVA and Schaundinn fixative that is free of formalin and mercury.
- Can be used for concentration techniques and permanent stained smears.
- Some products can be used for performing fecal immunoassay.
Clinical Parasitology Laboratory
- MACROSCOPIC ANALYSIS: determines the color and consistency of the stool submitted, which may indicate the presence of parasites.
- MICROSCOPIC ANALYSIS: detects the presence of parasites in stool specimens and involves three distinct procedures: sedimentation, flotation, and staining techniques.
Stains
- TRICHROME STAIN (Wheatley Trichrome): a widely used permanent stain with a long shelf life and easy procedure.
- IRON HEMATOXYLIN: considered time-consuming, but reveals excellent morphology of intestinal protozoa.
- SPECIALIZED STAINS: Acid-fast stain (detection of oocysts of Cryptosporidium, Isospora, and Cyclospora), Modified iron hematoxylin (detection of acid-fast parasites), and Modified trichrome stain (detection of spores of microsporidia).
Stool Screening Methods
- Alternative tests for detection of parasitic infection that use monoclonal antibodies to detect antigen in patient specimens.
- Examples of rapid tests: Enzyme Immunoassay, Direct Fluorescent Antibody, and Membrane Flow Cartridge Antibody.
Other Specimens and Laboratory Techniques
- Examination of stool specimens may not detect parasites in some cases.
- Additional procedures, such as culture, can be performed to reveal the presence of specific parasites.
Immunologic Testing
- Includes methods for antigen and antibody detection.
- Antigen detection is more reliable, and a positive test result indicates current infection.
- Antibody detection is more complex and must be interpreted cautiously.
Reporting of Results
- A positive specimen report should state the scientific name (genus and species), along with the stage that is present (e.g., cyst, trophozoite, larvae, eggs, adults).
- Presence of blood cells should be reported semi-quantitatively (rare, few, moderate, many).
- Fecal immunoassays should indicate the presence of antigens.
This quiz covers the concentration method used in parasitology to detect small numbers of parasites. It explains the process of preparing a microscope slide and staining to observe detailed morphology of protozoa cysts and trophozoites.
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