Question 1

For which of the following parasites might the examination of as many as six specimens be needed in order to recover the parasite?

Accepted Answer

G. lamblia adheres to the intestinal mucosa and appears intermittently in feces; therefore, three to six samples may be needed to successfully find the organisms.

Question 2

If patients must be purged to enhance recovery of parasites, any of the following enemics may be used EXCEPT:

Accepted Answer

Oils such as castor or mineral oil or suppositories may not be used because oil droplets will obscure the viewing of amoeba.

Question 3

The chemical found in fecal preservatives that enhances adhesion of parasites to slides prepared for trichrome stain is:

Accepted Answer

PVA provides the best adhesion properties of the various preservatives listed.

Question 4

When performing an ocular micrometer calibration procedure for the 40x objective, the technologist noted that the 40 mark on the ocular micrometer scale lined up exactly with the 0.09-mm line on the stage micrometer scale. The width in millimeters for each ocular scale division is:

Accepted Answer

Each ocular division is equal to 0.09mm/40 or 0.00225mm. Because there are 1000 µm in one millimeter, there are 2.25 µm in each ocular micrometer division (0.00225 x 1000 = 2.25).

Question 5

Charcot-Leyden crystals are occasionally observed in stool. These crystals are probably from breakdown products of:

Accepted Answer

Charcot-Leyden crystals are thought to be disintegrating eosinophilic granules.

Question 6

The most sensitive method used to recover Acanthamoeba spp. from eye-care solutions or corneal samples is the:

Accepted Answer

A non-nutrient agar plate seeded (inoculated) with E. coli bacteria is inoculated with a patient sample or a possibly infected eye-care solution to detect the presence of ameba. If Acanthamoeba are present, they will feed on the bacteria and propagate, leading to increased numbers of ameba, which can be observed directly on the plate when it is examined using a microscope.

Question 7

Modified acid-fast stain is used to visualize several parasites including Cryptosporidium parvum. The modification that differentiates this method from that used to stain mycobacteria (AFB) is that in the parasite method:

Accepted Answer

A weaker decolorizer is needed because parasitic cells do not bind the dye as tightly as AFB cells.

Question 8

Artifacts found in feces that can be confused with eggs or cysts are:

Accepted Answer

Pollen grains commonly appear similar to eggs or cysts.

Question 9

Artifacts found in feces that can be confused with Entamoeba coli are:

Accepted Answer

Macrophages and especially white blood cells may be confused with Entamoeba coli or Entamoeba histolytica.

Question 10

Artifacts found in feces that can be confused with Strongyloides stercoralis larva are:

Accepted Answer

Plant hairs commonly appear similar to Strongyloides or hookworm larva.

Question 11

The best method to recover pinworm eggs is the:

Accepted Answer

Female pinworms do not release their eggs inside the host's intestine, so eggs are not found in feces. The cellophane tape test is used to recover eggs found around the anus after migrating females leave the lower intestine and die outside the host. See text page 164.

Question 12

Which of the following eggs is not easily recovered using the zinc sulfate technique?

Accepted Answer

Operculated eggs are relatively heavy and do not float well. Other nonfloaters include schistosome and infertile Ascaris spp. eggs.

Question 13

When using a trichrome stain to reveal parasites, an amoeba's karyosomes will stain:

Accepted Answer

Various structures retain different pigments. The karyosomes appear ruby red. Cytoplasm appears as blue-green to pink in color.

Question 14

Thick blood smears for malaria examinations are "laked" before staining by:

Accepted Answer

Adequate exposure to Giemsa-buffered water (10 minutes) is needed to completely lyse RBCs. See text pages 168 and 209.

Question 15

If both thick and thin blood smears for malaria examination are negative, the best method to confirm the negative results is a(n):

Accepted Answer

When neither thick nor thin blood smears for malaria examination reveal parasites, preparing a buffy coat smear may concentrate parasites, leading to a positive recovery of a low-level malaria infection.

Question 16

When filariasis is suspected, which of the following will improve the chances to recover parasites?

Accepted Answer

The Knott's technique concentrates blood parasites by centrifuging the blood sample before staining the concentrate with Giemsa stain. See text page 169.

Question 17

Six Giardia lamblia were seen in a 10-field scanning of a trichrome-stained smear. The correct report of this finding is:

Accepted Answer

The usual key for reporting significant findings is ? 2, few; 3-9, moderate; > 10, many.

Question 18

The technique used to reveal microsporidia in fecal smears is the:

Accepted Answer

Microsporidia do not stain using the Wheatley trichrome stain. Weber and Green modified the Wheatley trichrome stain by increasing the chromotrope 2R dye concentration and increasing the staining time to correct this problem.

Question 19

Which of the following parasites is autofluorescent?

Accepted Answer

Only Cyclospora spp. autofluoresces, which is a useful characteristic because it is acid-fast variable. The other parasites are revealed by acid-fast stain.

Question 20

All of the following parasites may have diagnostic forms present in sputum EXCEPT:

Accepted Answer

T. spiralis larvae penetrate blood vessels and then travel directly to tissues. The larvae of Ascaris spp. and hookworms migrate through the liver to the lungs before returning to the intestinal tract. Paragonimus spp. adults migrate to the lungs and release eggs into the bronchi, which are recovered in sputum.

Quiz 8: Clinical Laboratory Procedures