Deck 15: Ova and Parasites

Question 1

A formed stool specimen is received in the clinical laboratory for ova and parasite examination at 3 p.m. The specimen sat at room temperature in the ordering physician's office since 9:00 a.m. this morning. You will

A) reject the specimen.
B) perform the examination STAT due to the time lag.
C) place the specimen in preservative and process the next day.
D) call the office for an additional specimen.

Answer 1

place the specimen in preservative and process the next day.

Question 2

The gastrointestinal laboratory sends a stool specimen for ova and parasite examination after a patient receives a barium enema. You should

A) place the specimen in preservative.
B) perform the examination as soon as possible.
C) reject the specimen.
D) request a duodenal aspirate in addition to the stool specimen.

Answer 2

reject the specimen.

Question 3

Paragonimus westermani, Entamoeba histolytica, and Pneumocystis jiroveci can all potentially be found in

A) blood.
B) urine.
C) stool.
D) sputum.

Answer 3

sputum.

Question 4

The preferred anticoagulant for detection of parasites in blood is

A) none.
B) EDTA
C) heparin
D) SPS.

Question 5

A preserved stool specimen is received in the microbiology laboratory. A two-vial system was used. One vial contains 10% formalin and the second vial contains polyvinyl alcohol (PVA). How will the vials be used?

A) Formalin vial for concentration procedure and PVA vial for permanent smear
B) PVA vial for concentration procedure and formalin for permanent smear
C) PVA for permanent smear and the remainder along with formalin for concentration procedure
D) Only the formalin vial is needed for concentration and permanent smear

Question 6

A 24-hour collection of ___________________ can be used to detect Schistosoma haematobium ova.

A) stool
B) sputum
C) duodenal aspirate
D) urine

Question 7

The ability of some blood parasites to migrate in the blood during specific times of the day is called

A) episodicality
B) seasonality
C) cyclicity
D) periodicity

Question 8

Wet preparations of stool, using saline or iodine, are examined for the presence of

A) ova.
B) larvae.
C) protozoa.
D) all of the above.
E) a and b.

Question 9

Stained smears of stool are examined for the presence of

A) ova.
B) larvae.
C) protozoa.
D) all of the above.
E) b and c.

Question 10

After concentration of stool, only an iodine wet preparation is examined because

A) the parasites are dead and no longer exhibit motility.
B) saline interferes with the reagents used for concentration.
C) saline does not provide enough contrast for detection of parasites.
D) saline distorts the parasites present.

Question 11

One major advantage of the formalin-ethyl acetate concentration procedure over the zinc sulfate flotation concentration procedure is

A) parasites present are killed.
B) ease of performance and consistency of results.
C) the concentrate is cleaner and easier to read.
D) an iodine wet preparation is not necessary.

Question 12

When preparing an iodine wet preparation of fresh stool, the final suspension should be

A) thick so the number of parasites will be increased.
B) very thin so the organisms can be easily seen.
C) thin enough to read print through it.
D) thick to ensure recovery of ova and larvae as well as protozoa.

Question 13

When calibrating an ocular micrometer for a microscope, one must remember to perform the procedure

A) annually.
B) on each microscope used for examination.
C) on each objective on the microscope.
D) all of the above.

Question 14

Acid-fast stains are necessary to ensure detection of the presence of _____________________ in stool.

A) Cryptosporidium spp.
B) Cyclospora spp.
C) Isospora spp.
D) all of the above
E) a and b

Question 15

The trichrome stain is most commonly used for stool smear specimens. The protozoa appear __________________ while the background appears ___________________.

A) red, blue
B) light blue-green, green
C) blue-gray, gray
D) brown, clear

Question 16

Thick blood smears for the presence of malaria must be ______________ prior to staining.

A) lysed
B) heat fixed
C) fixed in methanol
D) made with a feathered edge

Question 17

A physician suspects a patient has an infection with Enterobius vermicularis. He must provide the patient with instructions on how to collect

A) a stool specimen.
B) a urine sample.
C) a swab of the perianal area.
D) a lower respiratory specimen.

Question 18

When preparing an iodine wet preparation of a concentrated stool, the Lugol's iodine stock should be diluted

A) 1:10 with saline.
B) 1:5 with distilled water.
C) 1:10 with distilled water.
D) 1:5 with saline.

Question 19

One disadvantage of performing a molecular biology assay for parasites is

A) that the procedure lacks sensitivity and specificity.
B) it requires expertise in interpretation of results.
C) its slow turn around time.
D) it may only detect one or two specific parasites.

Question 20

Which of the following procedures for the detection of parasites is riddled with cross-reactions, variable patient response, and technically demanding for most clinical laboratories?

A) Serologic assay
B) Enzyme immunoassay
C) Direct fluorescent antibody
D) Molecular biology assay