Artifacts and confusers in Parasitology

There are a number of structures close to parasites, but in reality they are not.These structures, known as artifacts and confusers in parasitology, are mainly found in samples of stools and blood.Such stool artifacts and confusers can be caused by disease processes, drugs and/or dietary habits.The presence in stool of free-living organisms caused by the contact of specimens with water, sewage or soil can often cause confusion.Artifacts and confusers, such as stain precipitation, anomalies in red blood cells, including Howell-Jolly bodies, and clumping of platelets, can be seen on blood smears.

In addition to the common artifacts and confusers mentioned above, others can be seen in sample submitted for examination.Some of these confusers are free-living amebae, flagellates, ciliates and nematodes.Accidental ingestion of parasites in which humans are not part of their life cycle can also lead to confusion.In this article, fourteen of the most common artifacts and confusers are briefly discussed.

WHITE BLOOD CELLS

Polymorphonuclear white blood cells (WBCs), which typically have an average size of 15 μm, are often mistaken for amebic cysts, especially Entamoeba histolytica, the average size of which is 12 to 18 μm.

In patients with ulcerative colitis, bacterial dysentery or intestinal amebiasis, WBCs are usually present.In addition to falling into the amebic cyst size range, these WBCs have a two-to-four-lobed nucleus that is similar to the nucleus of E. histolytica. Although these WBC lobes can appear as separate nuclei, thin chromatin bands connect them.Nuclear inclusions of protozoans such as karyosomes and peripheral chromatin are not present in WBCs.Careful microscopic focus is required because these bands are often hard to detect.

Mononuclear WBCs, also known as macrophages or monocytes, can range from 28 to 62 μm in size (less in permanently stained preparations) and are closely similar to E.Histolytica trophozoite, 8 to 65 μm long.Both structures can ingest red blood cells and debris, but only polymorphonuclear WBCs are ingested by the macrophages.The macrophage has an irregular nucleus, which is often missing when examined.Although the macrophage size intersects with E.Histolytica,the macrophage may be considerably smaller (5 to 10 μm).Red-stained round bodies in the macrophages can be seen.

white blood cells in stools
white blood cells in stools

POLLEN GRAINS

Thick – walled pollen grains look like Taenia spp ‘s eggs. But they are smaller, from 12 to 20 μm. Grains of pollen may appear round or symmetrically lobed. There are no notable interior structures, unlike Taenia spp egg

Pollen grain artifact in stools
Pollen grain artifact in stools

VEGETABLE CELLS

Cells of vegetables can easily be confused with eggs of helminth.These cells are typically large and roundish in shape and can be up to 150 μm in size.Usually, thick cell walls are present.The inner part of plant cells is unorganized and often consists mainly of large vacuoles.

vegetable artifact in stools
vegetable artifact in stools

VEGETABLE SPIRALS

The vegetable spirals often resemble the larvae of helminth in form and size.However, in contrast to the larvae of helminth, vegetable spirals have no head or tail area.Vegetable spirals are easily distinguished by their ladder-like appearance from parasite forms.The ladder consists of a series of closely spaced rungs.

vegetable spiral artifact in stools
vegetable spiral artifact in stools

CHARCOT-LEYDEN CRYSTALS

Of all the confusers and artifacts discussed in this article, Charcot-Leyden crystals have the greatest clinical significance.They are usually found in stool or sputum specimens and are shown.The presence of these diamond-shaped crystals, which develop from eosinophilic breakdown products, shows that there has been an immune response of unknown origin.Since the presence of parasites can cause such an immune response, it is important to closely examine specimens containing Charcot-Leyden crystals.

Charcot-Leyden crystals in stools
Charcot-Leyden crystals in stools

YEAST

The size of the round to oval yeast cells is 4 to 8 μm and can be confused with protozoan cysts, in particular Entamoeba hartmanni (5 to 12 μm), Entamoeba nana (4 to 12 μm) and Entamoeba hominis (3 to 10 μm).In addition, there is a considerable similarity of a yeast cell to the cryptosporidium oocyst (4 to 6 μm).Like other artifacts and confusers, yeast cells usually do not have certain internal structures.However, small granules similar to karyosomes can be seen from time to time.Yeast can easily be differentiated from parasites when seen in the budding phase.

yeast cells in stools
yeast cells in stools

PLANT HAIR

Plant hair may resemble large and shaped Helminth larvae.Plant hair can also seem to have an undescribed internal structure.Plant hair does not have diagnostic structures such as the mouth cavity, esophagus, intestine or genital primordium after further examination.There is no region of head or tail.

plant hair in stools
plant hair in stools

PLANT MATERIAL

Plant material can be 12 to 150 μm in diameter and resemble helminth eggs, especially unfertilized Ascaris lumbricoides (38 to 45 μm) in size and shape.This artifact is usually round to oval and can have a certain cell wall or not.Plant material is often rough in appearance and may have hair (pseudo cilia) from the periphery of the plant.The cell’s inside looks like a cluster of strange vacuoles.

plant material in stools
plant material in stools

FUNGAL ELEMENTS

The size and shape of the protozoan cysts can be similar to fungal elements. The lack of internal structures makes these artifacts easy to distinguish from parasitic forms.

fungi elements in stools
fungi elements in stools

EPITHELIAL CELLS

Epithelial cells often show a striking similarity to the size and shape of amebic trophozoite.Moreover, epithelial cells have a single nucleus and often have a separate cell wall, just like the amebic trophozoites.Epithelial cells lack the typical amebic inner structures of the trophozoite.For instance, the epithelial cell cytoplasm is usually smooth and does not contain inclusions.However, the large epithelial nucleus can consist of a large chromatin mass which is similar to a nucleus.

epithelial cell in urine
epithelial cell in urine

STARCH CELLS

Round to irregular round starch cells, also known as starch granules, measure less than 10 μm and may at first glance appear to be protozoan cysts, especially E.hartmanni and E.nana (both measures 5 to 12 μm in length).These cells are easily distinguished from parasitic forms because internal structures are lacking.A non-described mass within the cell is often present and can look like a nucleus.Further investigation of this structure shows that there is no karyosome or peripheral chromatin. Starch cells can also be differentiated from parasites due to their dark blue black appearance when stained with iodine.

starch cells in stools
starch cells in stools

CLUMPED OR FUSED PLATELETS

Clumped or fused platelets often appear on blood film smears in Giemsa and may be mistaken for malaria parasites, particularly the young trophozoite form.In contrast to a malaria parasite that typically appears as a blue cytoplasm with a red chromatin, clumped or fused plates appear in different shades of purple.Malaria parasites also have a clearer outline than clumped or merged platelets.

clumped platelets in peripheral blood
clumped platelets in peripheral blood smear

STAIN PRECIPITATE

Giemsa-stain precipitate can be seen on blood smears and can be mistaken for parasites of malaria. Stain precipitate is usually bluer in color and varies in size and shape than malaria parasites.

stain precipitate in peripheral blood smear
stain precipitate in peripheral blood smear

RED CELL ABNORMALITIES

Red blood cell anomalies, such as Howell Jolly or Cabot’s rings, may occur on the blood smears of Giemsa. These abnormalities can easily be distinguished from malaria parasites by their various staining properties.

howell jolly in peripheral blood smear
howell jolly in peripheral blood smear

CONCLUSION

Artifacts and confusers are defined as microscopic forms which look like parasites but are not parasites.It is therefore important to screen all specimens carefully and take into account all the characteristics of suspicious microscopic forms before deciding their final identity.One artifact, Charcot-Leyden crystals in particular, is important and should be reported when viewed because it indicates an immune response that may or may not be caused by a parasite infection.Before deciding that these specimens have no parasites, careful screening should be carried out.


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About the Author: Arthur Westmann

DEFFE ARTHUR (AMOEBAMANN) is the founder and author of MLTGEEKS and MLTEXPO.He’s from Cameroon and is currently a Final year State Medical Laboratory Technician (MLT MA). Beyond lab works, he’s a passionate internet user with a keen interest in web design and blogging. Furthermore He likes traveling, hanging around with friends and social networking to do in his spare time.

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