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What is a limitation of diagnosing parasitic infections through microscopic examination?
What is a limitation of diagnosing parasitic infections through microscopic examination?
What is the primary purpose of using the direct smear method in microscopic examination?
What is the primary purpose of using the direct smear method in microscopic examination?
Which statement is true regarding stool sample collection for parasitic diagnosis?
Which statement is true regarding stool sample collection for parasitic diagnosis?
Which staining method can be added to a saline preparation to highlight nuclei and distinguish between cell types?
Which staining method can be added to a saline preparation to highlight nuclei and distinguish between cell types?
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What should a patient stop taking three days before stool sample analysis?
What should a patient stop taking three days before stool sample analysis?
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What additional component is added to a saline preparation to facilitate the identification of protozoa?
What additional component is added to a saline preparation to facilitate the identification of protozoa?
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What is the acceptable condition of stool samples that should be avoided?
What is the acceptable condition of stool samples that should be avoided?
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In the sedimentation method, what role does centrifugation play?
In the sedimentation method, what role does centrifugation play?
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What characteristic features of stool can indicate the presence of adult parasites?
What characteristic features of stool can indicate the presence of adult parasites?
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In a clinical examination for parasitic infections, which factor is NOT considered during history taking?
In a clinical examination for parasitic infections, which factor is NOT considered during history taking?
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Which method is recommended if negative results are obtained from the direct smear?
Which method is recommended if negative results are obtained from the direct smear?
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What is the advantage of using formalin in the sedimentation process?
What is the advantage of using formalin in the sedimentation process?
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Which method is NOT used to confirm a parasitic infection diagnosis?
Which method is NOT used to confirm a parasitic infection diagnosis?
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What should be done if a stool sample cannot be analyzed immediately?
What should be done if a stool sample cannot be analyzed immediately?
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Which type of preparation allows for the examination of motile trophozoites and larvae effectively?
Which type of preparation allows for the examination of motile trophozoites and larvae effectively?
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What is the main purpose of filtration in the sedimentation method?
What is the main purpose of filtration in the sedimentation method?
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What is a disadvantage of the flotation method in parasitology?
What is a disadvantage of the flotation method in parasitology?
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Which technique is primarily used for identifying protozoan flagellates?
Which technique is primarily used for identifying protozoan flagellates?
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Which of the following is NOT a focus of the Kato-Katz technique?
Which of the following is NOT a focus of the Kato-Katz technique?
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What is the basis of the Baermann technique for detecting nematodes?
What is the basis of the Baermann technique for detecting nematodes?
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Which of the following is NOT an application of the Kato-Katz technique?
Which of the following is NOT an application of the Kato-Katz technique?
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In which method do the larvae move into water from feces in order to be collected?
In which method do the larvae move into water from feces in order to be collected?
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What is a primary advantage of using permanent stained smears in stool examination?
What is a primary advantage of using permanent stained smears in stool examination?
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Which of the following eggs can be quantified using the Kato-Katz technique?
Which of the following eggs can be quantified using the Kato-Katz technique?
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What is a significant advantage of molecular biological techniques in parasite detection?
What is a significant advantage of molecular biological techniques in parasite detection?
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Which statement best describes the utility of antibody detection methods in immunological assessments?
Which statement best describes the utility of antibody detection methods in immunological assessments?
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What is a challenge associated with DNA probe and PCR-based assays?
What is a challenge associated with DNA probe and PCR-based assays?
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Which of the following describes a limitation of filter paper culture when used for nematode larvae?
Which of the following describes a limitation of filter paper culture when used for nematode larvae?
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What is the main role of labeling DNA probes in molecular assays?
What is the main role of labeling DNA probes in molecular assays?
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Which indirect immunological method is known for its quantitative assessment?
Which indirect immunological method is known for its quantitative assessment?
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What type of samples are typically analyzed using PCR with diagnostic primers?
What type of samples are typically analyzed using PCR with diagnostic primers?
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In which aspect is the Latix agglutination test particularly noted?
In which aspect is the Latix agglutination test particularly noted?
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Study Notes
Laboratory Diagnosis of Parasitic Infections
- Failure to isolate a parasite does not rule out infection.
- Many protozoa are only identifiable through microscopic examination.
- This method is time-consuming and labor-intensive with limitations.
Diagnosis of Infected Cases
- History (age, occupation, residence, prior infection)
- Complaint
- Clinical examination
- Investigations:
- Laboratory tests
- Radiology
- Surgical intervention (exploratory)
- Presumptive diagnosis
- Confirm diagnosis
Diagnosis of Parasites
-
Direct Methods:
- Urine
- Stool
- Sputum
- Biopsy
- Blood
-
Indirect Methods:
- Indirect hemagglutination (IHA) test
- Latex agglutination
- Immunofluorescence assay
- ELISA
-
Molecular Methods:
- PCR
- DNA probes
Stool Sample Collection
- Collect in a clean, dry, screw-top container.
- Label completely with patient information (name, DOB, date of sample).
- Avoid contamination with urine, soap, or disinfectants (destroys amoebae).
- Handle specimens carefully, wash hands.
- Samples should be fresh (especially protozoa, ciliates).
- Preserve specimens as soon as possible.
- Stop antibiotics, anti-parasitics, barium, enemas, and oily laxatives 3 days before testing.
- Liquid and soft stool specimens examined within 15 minutes.
Stool Examination
-
Macroscopic:
- Consistency
- Color
- Composition
-
Microscopic:
- Temporary
- Direct saline smear
- Iodine smear
- Concentration techniques
- Floatsation (e.g., saline, formalin-ether)
- Zinc sulphate
- Sheather's sugar
- Temporary
-
Others:
- Culture
- Cellophane tape
- Baermann technique
- Ova quantitation (Stoll & Kato)
Microscopic Examination - Direct Smear Method
- Fast, simple procedure, provides quick answers when possible.
- Used as a screening test to check trophozoite motility.
- Prepared directly from fecal material or concentrated specimen.
- Negative results require confirmation with concentration methods or permanent stain methods.
Stool Examination - Temporary Staining
- Wet mount:
- Saline smear
- Iodine smear
- Detect motile trophozoites, and larvae, ova, and cysts.
- Stain glycogen and nuclei of cysts, differentiating from WBCs.
- Stained saline preparation with methylene blue
- Coverslip for viewing
- Distinguish polymorphs from mucosal cells; use eosin for differential staining of protozoa (e.g., amoebae).
Stool Examination - Concentration Techniques
- Increase the relative number of parasites with scanty infections.
- Reduce background fecal debris
-
Sedimentation:
- Heavy eggs (Ascaris)
- Operculated eggs (Trematodes)
- Larvae (Strongyloides)
- Cysts
-
Floatation:
- Non-operculated eggs (Schistosoma)
- Cestodes
- Nematodes (hookworms)
- Cysts
Stool Examination - Sedimentation Method
- All egg and cyst types recoverable
- Parasites settle quickly by centrifugation.
- Large particles removed by filtration.
- Formol-ether and ethyl acetate to remove organic materials, thus increasing efficiency and detection.
Stool Examination - Flotation Method
- Parasites recover in surface films.
- Cleaning better than sedimentation.
- Disadvantage:
- Operculated and dense eggs don't concentrate well.
- Protozoan cysts can become distorted, making identification difficult
Stool Examination - Permanent Stained Smears
- Useful for identifying protozoa (especially flagellates), not helminths (helminths and larvae distort during staining).
- Use when direct wet prep or concentration doesn't detect parasite.
- Staining procedures:
- Iron hematoxylin
- Trichrome
- Giemsa
- Modified Ziehl-Neelsen
- Modified Safranin
Stool Examination - Kato Technique
- A technique for identifying and quantifying soil-transmitted helminths and schistosome infections.
- Counts eggs per gram of feces
Stool Examination - Stoll's Technique
- A method for counting eggs in feces
- Weighs 3 grams of stool mixed with water to make 1/15 dilution
- Uses a pipette to measure 150 microliters for microscopic examination.
- Used for identifying Ascaris, whipworms, hookworms, and S. mansoni.
Stool Examination - Baermann Technique
- Based on active migration of larvae from feces.
- Feces suspended in water, larvae sink to the bottom, collected for identification.
- Used for detecting nematode larvae.
Indirect Immunological Methods
- Antigen Detection: Specific, accurate, and active/early infection detection
-
Antibody Detection: Antibodies remain in serum months after infection. Antibody tests detect the antibodies produced by the body in response to a parasite infection.
- Hemagglutination Inhibition Test
- Latex Agglutination Test
- Direct Fluorescent Antibodies
- ELISA
- Complement Fixation Test
- Double Electro Immuno Diffusion
Molecular Methods
- DNA probe/PCR-based assays to detect parasites accurately.
- Independent of previous infection.
- Distinguishes morphologically similar organisms.
- DNA Probes: Complementary nucleic acid sequences detect parasite's presence via hybridization.
- Polymerase Chain Reaction (PCR): Detects parasites via DNA amplification from fecal samples; electrophoresis to resolve fragments.
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Description
Test your knowledge on the laboratory diagnosis of parasitic infections. This quiz covers isolation methods, direct and indirect diagnostic techniques, as well as sample collection protocols. Ideal for students in medical or health-related fields.
