Parasite Detection in Blood Smears

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Questions and Answers

What is a limitation of direct wet preparation?

It requires a large portion of stool

It cannot demonstrate motility

It cannot detect helminth eggs

It cannot be performed on fixed specimens (correct)

What is a possible cause of black stool?

Bile duct obstruction

Lower GI bleeding

Upper GI bleeding (correct)

Helminth infection

What type of organism can be detected using direct wet preparation?

Fungi

Protozoan trophozoite (correct)

Bacteria

Virus

What is the purpose of adding iodine to the stool mixture in direct wet preparation?

To improve visualization of organisms Signup and view all the answers

What is a possible cause of red stool?

Lower GI bleeding Signup and view all the answers

What is a characteristic of direct saline wet preparation?

It can demonstrate motility Signup and view all the answers

What is a possible cause of pale yellow stool?

Bile duct obstruction Signup and view all the answers

What is an alternative to direct wet preparation?

Concentration technique Signup and view all the answers

What is a disadvantage of PVA-preserved specimens containing Schaundinn solution?

Exposure may lead to potential health problems due to mercuric chloride Signup and view all the answers

What is an alternative to the use of PVA and Schaundinn fixative?

Sodium acetate formalin (SAF) Signup and view all the answers

What is the significance of the color of stool in macroscopic analysis?

It may indicate a patient's condition or status Signup and view all the answers

What is the purpose of macroscopic analysis in stool specimen processing?

To examine the stool for gross abnormalities Signup and view all the answers

What is a characteristic of a soft or liquid stool in macroscopic analysis?

It suggests the presence of protozoan trophozoites Signup and view all the answers

What is the purpose of microscopic analysis in stool specimen processing?

To detect the presence of parasites in stool specimen Signup and view all the answers

What is a characteristic of formed stools in macroscopic analysis?

They are likely to contain protozoan cysts Signup and view all the answers

What is an advantage of single-vial systems in stool specimen processing?

They are free of formalin and mercury Signup and view all the answers

What is a disadvantage of PVA-preserved specimens?

They are difficult to dispose Signup and view all the answers

What is the significance of stool consistency in macroscopic analysis?

It may serve as an indication of potential parasite present Signup and view all the answers

Which of the following parasites can be recovered from examining sigmoid material?

Microsporidia and E.histolytica Signup and view all the answers

What is the importance of examining material from ulcers obtained by aspiration or scraping immediately?

To prevent loss of parasites Signup and view all the answers

What is the typical blood sample processing procedure?

Preparation of thick and thin smears, staining with permanent stain, then examined microscopically Signup and view all the answers

What is the purpose of collecting five daily specimens for Enterobius vermicularis (pinworms)?

To rule out negative infection Signup and view all the answers

When is the best time to collect a specimen for Enterobius vermicularis (pinworms)?

In the morning before the patient washes or defecates Signup and view all the answers

What is the purpose of using the Knott technique in blood sample processing?

To concentrate microfilariae Signup and view all the answers

What is the advantage of using thick smears in blood sample processing?

It is frequently satisfactory for screening purposes Signup and view all the answers

What is the purpose of using cellophane tape preparation?

To recover Enterobius vermicularis (pinworms) eggs Signup and view all the answers

What type of parasite is often detected using skin snips?

Onchocerca volvulus Signup and view all the answers

What is the purpose of a 30-minute incubation period in skin snip examination?

To allow the microfilariae to migrate into the saline Signup and view all the answers

Which of the following would require quantitation in an assay?

Blastocystis hominis Signup and view all the answers

What is the typical container used to collect material obtained via mouth scrapings and nasal discharge?

A clean airtight collection container Signup and view all the answers

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 Signup and view all the answers

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 Signup and view all the answers

What is a characteristic of microfilariae in a saline solution?

They are motile and can be seen migrating into the saline Signup and view all the answers

Which of the following parasites can be detected using mouth scrapings and nasal discharge samples?

Motile larvae Signup and view all the answers

What is the primary reason for collecting blood specimens without anticoagulant for parasite detection?

To prevent distortion of parasite morphology Signup and view all the answers

Which type of blood sample is ideal for observing the morphology of parasites?

Fingertip or earlobe blood Signup and view all the answers

What is the primary purpose of the Knott Technique?

To concentrate blood specimens suspected of containing low numbers of microfilariae Signup and view all the answers

What is the recommended time frame for preparing a blood smear if malaria is suspected?

Within 1 hour of collection Signup and view all the answers

What is the primary specimen of choice for the detection of Ascaris lumbricoides and Hookworms?

Early morning stool sample Signup and view all the answers

What is the purpose of using N-acetylcysteine in the examination of stool samples?

To facilitate the detection of Ascaris lumbricoides and Hookworms Signup and view all the answers

What is the medium used for the recovery of Leishmania spp. and Trypanosoma cruzi?

NNN medium Signup and view all the answers

Why is it essential to ensure that capillary blood is free-flowing and not contaminated with alcohol?

To ensure satisfactory results in blood smears Signup and view all the answers

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

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Description

Learn about the techniques and precautions for collecting blood samples for parasite detection, including the importance of aseptic technique and proper collection methods.