42 Questions
What is a limitation of direct wet preparation?
It cannot be performed on fixed specimens
What is a possible cause of black stool?
Upper GI bleeding
What type of organism can be detected using direct wet preparation?
Protozoan trophozoite
What is the purpose of adding iodine to the stool mixture in direct wet preparation?
To improve visualization of organisms
What is a possible cause of red stool?
Lower GI bleeding
What is a characteristic of direct saline wet preparation?
It can demonstrate motility
What is a possible cause of pale yellow stool?
Bile duct obstruction
What is an alternative to direct wet preparation?
Concentration technique
What is a disadvantage of PVA-preserved specimens containing Schaundinn solution?
Exposure may lead to potential health problems due to mercuric chloride
What is an alternative to the use of PVA and Schaundinn fixative?
Sodium acetate formalin (SAF)
What is the significance of the color of stool in macroscopic analysis?
It may indicate a patient's condition or status
What is the purpose of macroscopic analysis in stool specimen processing?
To examine the stool for gross abnormalities
What is a characteristic of a soft or liquid stool in macroscopic analysis?
It suggests the presence of protozoan trophozoites
What is the purpose of microscopic analysis in stool specimen processing?
To detect the presence of parasites in stool specimen
What is a characteristic of formed stools in macroscopic analysis?
They are likely to contain protozoan cysts
What is an advantage of single-vial systems in stool specimen processing?
They are free of formalin and mercury
What is a disadvantage of PVA-preserved specimens?
They are difficult to dispose
What is the significance of stool consistency in macroscopic analysis?
It may serve as an indication of potential parasite present
Which of the following parasites can be recovered from examining sigmoid material?
Microsporidia and E.histolytica
What is the importance of examining material from ulcers obtained by aspiration or scraping immediately?
To prevent loss of parasites
What is the typical blood sample processing procedure?
Preparation of thick and thin smears, staining with permanent stain, then examined microscopically
What is the purpose of collecting five daily specimens for Enterobius vermicularis (pinworms)?
To rule out negative infection
When is the best time to collect a specimen for Enterobius vermicularis (pinworms)?
In the morning before the patient washes or defecates
What is the purpose of using the Knott technique in blood sample processing?
To concentrate microfilariae
What is the advantage of using thick smears in blood sample processing?
It is frequently satisfactory for screening purposes
What is the purpose of using cellophane tape preparation?
To recover Enterobius vermicularis (pinworms) eggs
What type of parasite is often detected using skin snips?
Onchocerca volvulus
What is the purpose of a 30-minute incubation period in skin snip examination?
To allow the microfilariae to migrate into the saline
Which of the following would require quantitation in an assay?
Blastocystis hominis
What is the typical container used to collect material obtained via mouth scrapings and nasal discharge?
A clean airtight collection container
What is the purpose of making a small cut into the skin using a razor blade in skin snip collection?
To collect a skin sample
Why are permanent stains sometimes used in the examination of mouth scrapings and nasal discharge samples?
To detect parasites that are not visible with a wet prep
What is a characteristic of microfilariae in a saline solution?
They are motile and can be seen migrating into the saline
Which of the following parasites can be detected using mouth scrapings and nasal discharge samples?
Motile larvae
What is the primary reason for collecting blood specimens without anticoagulant for parasite detection?
To prevent distortion of parasite morphology
Which type of blood sample is ideal for observing the morphology of parasites?
Fingertip or earlobe blood
What is the primary purpose of the Knott Technique?
To concentrate blood specimens suspected of containing low numbers of microfilariae
What is the recommended time frame for preparing a blood smear if malaria is suspected?
Within 1 hour of collection
What is the primary specimen of choice for the detection of Ascaris lumbricoides and Hookworms?
Early morning stool sample
What is the purpose of using N-acetylcysteine in the examination of stool samples?
To facilitate the detection of Ascaris lumbricoides and Hookworms
What is the medium used for the recovery of Leishmania spp. and Trypanosoma cruzi?
NNN medium
Why is it essential to ensure that capillary blood is free-flowing and not contaminated with alcohol?
To ensure satisfactory results in blood smears
Study Notes
Disadvantages of PVA
- Contains mercuric chloride, which can be harmful to health
- Difficult to dispose of
- PVA-preserved specimens have a long shelf life when stored at room temperature
- Poor adhesion of liquid or mucoid specimens to slides
Alternative Single-Vial System
- Free of formalin and mercury
- Can be used for concentration techniques and permanent stained smears
- Some products can be used for performing fecal immunoassay
Sodium Acetate Formalin (SAF)
- Used in concentration techniques and permanent stained smears
- Viable alternative to PVA and Schaundinn fixative
- Mercury-free
Clinical Parasitology Laboratory
Specimen Processing
- Macroscopic analysis of stool involves determining color and consistency, and screening for gross abnormalities
- Stool consistency can indicate potential parasites present
- Soft or liquid stool may suggest presence of protozoan trophozoite
- In formed stools, protozoan cysts are likely to be recovered
Microscopic Analysis
- Done to detect presence of parasites in stool specimen
- Involves three distinct procedures: direct wet preparation, concentration technique, and permanent staining
Direct Wet Preparation
- Performed with unfixed stool mixed with saline or iodine
- Demonstrates motility of organisms
- Detects protozoan trophozoites, protozoan cysts, oocysts, helminth eggs, and larvae
Concentration Techniques
- Used to detect presence of parasites in stool specimen
Permanent Staining
- Used to detect presence of parasites in stool specimen
Stool Color and Possible Cause
- Black: upper GI bleeding, iron therapy, charcoal, or bismuth
- Red: lower GI bleeding, beets, or Rifampin
- Pale Yellow: bile duct obstruction
- White, Gray: barium sulfate
- Green: biliverdin, oral antibiotics, or green vegetables
Cellophane Tape Preparation
- Used to recover Enterobius vermicularis (pinworms) eggs
- Specimen of choice for recovering E. vermicularis eggs
- Adult female pinworm may also be seen
- Specimen must be collected in the morning before patient washes or defecates
Other Specimens for Parasitic Recovery
- Blood smears can be prepared from fresh whole blood without anticoagulant or from venipuncture collection without anticoagulant
- Blood from fingertip or earlobe yields the best morphology of parasites
- Specimens for parasite study must be collected by aseptic technique
- Anticoagulant causes distortion to the staining process and parasite morphology
Blood Sample Techniques
- Knott technique: designed to concentrate blood specimens suspected of containing low numbers of microfilariae
- Buffy coat slides: used in cancer patients
- Cultures: blood and other specimens may be performed to recover parasites
Urine and Genital Secretions
- Urine is the specimen of choice for detecting Schistosoma haematobium eggs
- Other parasites that might be seen on sputum or genital secretions include Schistosoma spp.
Skin Nips
- Useful in detecting Onchocerca volvulus
- Skin snips may be made using a specially designed tool or a razor blade
- The resulting material can be placed in saline and incubated for 30 minutes before microscopic examination
Learn about the techniques and precautions for collecting blood samples for parasite detection, including the importance of aseptic technique and proper collection methods.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
