Clinical Parasitology: Specimen Collection and Processing

Flashcards covering specimen collection protocols, storage, preservation methods, macroscopic/microscopic examination, and specialized parasitologic techniques based on the MTY1206 Clinical Parasitology lecture.

Definitive diagnosis

The demonstration of parasite or parasite components such as adults, egg, larvae, cysts, oocysts, trophozoites, and antigen.

Presumptive evidence

The detection of the host immune response (antibodies) to the parasites.

Typical stool collection protocol

Submission of $3$ specimens, with one collected every other day for $10$ days.

Amoebiasis collection protocol

Submission of $6$ specimens within a period of $14$ days.

Standard stool specimen size

A thumb-sized specimen for formed stool or $5-6$ tablespoons for watery stool.

Temporary storage temperature

Fecal samples should be stored in a $3-5℃$ refrigerator; they must never be frozen or incubated.

Stool to fixative ratio

One part stool to $3$ parts preservative.

5% Formalin

An all-purpose fixative concentration used specifically for protozoan cysts.

10% Formalin

An all-purpose fixative concentration used for helminth eggs and larvae.

Polyvinyl Alcohol (PVA)

A plastic resin incorporated into Schaudinn’s solution that serves to adhere stool onto a slide.

Mercuric Chloride

A toxic substance contained in Schaudinn’s solution and PVA-based fixatives.

Sodium Acetate-Acetic Acid Formalin (SAF)

A liquid fixative with a long shelf-life that does not contain Mercuric chloride.

Liquid or soft consistency

Stool consistency associated with trophozoites that must be processed within $30\,mins$.

Formed consistency

Stool consistency associated with cysts that should be processed within $3-4\,hrs$.

Dark red stool

Macroscopic observation indicative of upper GI bleeding.

Bright red stool

Macroscopic observation indicative of distal location bleeding.

Blood-tinged mucus (formed)

Macroscopic finding indicating the presence of trophic amoebae.

Bloody mucus (loose/liquid)

Macroscopic finding indicating amoebic ulcerations.

Charcot-Leyden Crystal

A specific microscopic finding in stool examination, often associated with immune response to parasites.

Direct Fecal Smear (DFS)

A technique using small amounts of unfixed stool and Saline/Iodine for the detection of trophic forms of amoeba and flagellates.

Iodine-stained Preparation

A preparation using Lugol’s or D’Antoni Iodine that kills trophozoites but enhances protozoan cysts.

Glycerine

The reagent used as a clearing solution in the Kato Thick Smear.

Malachite green

A reagent used in the Kato Thick Smear to minimize brightness.

Concentration Techniques

Procedures used in light infections to recover cysts, oocysts, helminth eggs, and larvae based on specific gravity.

40% HCl

A reagent in AECT used to dissolve albuminous material.

Ether

A reagent used in AECT and FECT to dissolve neutral fat.

Zinc Flotation Technique

A technique using $33\%$ Zinc Sulfate solution with an ideal specific gravity of $1.18$ to $1.20$.

Sheather’s Sugar Flotation Technique

A method using boiled sugar solution and Phenol; it is best for the recovery of Coccidian oocysts like Cryptosporidium.

Harada Mori

A test tube culture method used for hookworms, Strongyloides, and Trichostrongylus spp.

Kato-Katz Method

An egg counting procedure used to assess the intensity of infection or worm burden.

Perianal Swab

A collection method involving cellophane tape used to recover eggs of Enterobius vermicularis and Taenia spp.

Knott’s conc. technique

A specialized technique used primarily for examining blood specimens.

Xenodiagnosis

An advanced parasitologic technique listed for detecting specific infections.

Enterotest

A specialized technique used for the recovery of parasites from the intestinal tract.