How to differentiate artifacts in microscopy

A lot of structures appear like parasites but aren’t. In microscopy, artifacts and confusers are two categories of structures that are most often present in stool and blood samples. Stool objects and confusers may be triggered by disease mechanisms, medications, and/or eating patterns. It may be perplexing to see free-living organisms in stool, which is often influenced by specimen interaction with water, waste, or soil. Objects and confusers like ink precipitate, red blood cell abnormalities like Howell-Jolly bodies, and platelet clumping can all be seen on blood smears.

Artifact in stool wet preparation resembling parasite egg

In addition to the objects and confusers identified here, parasite research samples include a variety of other objects and confusers. Free-living amebae, flagellates, ciliates, and nematodes are all examples of these perplexers. Inadvertently ingesting parasite types in which humans are not a part of the life cycle may also create confusion.

Some of the common artifacts encountered during routine analysis are briefly discussed below.

WBC

WBCs, which are polymorphonuclear white blood cells with an average size of 15 m, are often mistaken for amebic cysts, especially those of Entamoeba histolytica, which have an average size of 12 to 18 m. WBCs are commonly used in ulcerative colitis, bacterial dysentery, and intestinal amebiasis patients. These WBCs have a two to four-lobed nucleus, close to the nucleus of E. histolytica, which fall into the amebic cyst size range. These WBC lobes tend to be independent nuclei, but they are connected by thin chromatin bands. WBCs lack protozoan nuclear inclusions including karyosomes and peripheral chromatin.

Mononuclear WBCs, also known as macrophages or monocytes, can range in size from 28 to 62 m (less on permanently stained preparations) and are very similar to the E. histolytica trophozoite, which is 8 to 65 m long. Red blood cells (RBCs) and debris may be absorbed by all structures, but only macrophages can absorb polymorphonuclear WBCs. On inspection, the macrophage has one irregularly shaped nucleus that is sometimes incomplete. While the macrophage size range is similar to that of E. histolytica, it is possible that the macrophage is smaller (5 to 10 m). In macrophages, red-staining circular bodies can be seen.

Pollen Grains

Pollen grains with thick walls are similar to Taenia spp. eggs, but they are smaller, measuring 12 to 20 m in length. Pollen grains may be symmetrically lobed or rounded. There are no significant internal buildings on Taenia.

Vegetable Cells

Vegetable cells may be mistaken for helminth larvae. These cells are normally broad and roundish oval or irregularly round in shape, with a diameter of up to 150 m. In most cases, dense cell walls are present. Vegetable cells’ interiors are disorganized and frequently tend to be mainly made up of large vacuoles.

Vegetable Spirals

In terms of size and shape, vegetable spirals mimic helminth larvae. Vegetable spirals, on the other hand, lack a head and tail area, unlike helminth larvae. The ladder-like nature of vegetable spirals sets them apart from parasitic shapes. A set of loosely spaced rungs make up the ladder.

Charcot-leyden crystals

Charcot-Leyden crystals are the most clinically important of all the confusers and objects. They’re commonly present in stool or sputum samples, and they’re recorded when they’re detected. The existence of these diamond-shaped crystals, which form from eosinophil breakdown products, signals the occurrence of an unexplained immune response. Since the presence of parasites could trigger such an immune response, it’s crucial to thoroughly inspect specimens containing Charcot-Leyden crystals.

Yeast

Protozoan cysts, especially those of Entamoeba hartmanni (5 to 12 m), Entamoeba nana (4 to 12 m), and Entamoeba hominis (3 to 10 m), can be confused with round to oval yeast cells measuring 4 to 8 m in dimension. Furthermore, a yeast cell (4 to 6 m) bears a remarkable similarity to a Cryptosporidium oocyst. Yeast cells, like the other objects and confusers, have no clear internal structures. Small granules resembling karyosomes are sometimes visible. When yeast is in the budding stage, it is easy to differentiate it from parasites.

Plant Hair

In size and shape, plant hair may resemble helminth larvae. Furthermore, plant hair can have an amorphous internal structure. Plant hair does not have diagnostic structures such as a buccal cavity, esophagus, intestine, or genital primordium, according to further review. There is no such thing as a head or tail area.

Plant Material

Plant material can be 12 to 150 m in diameter and resembles helminth eggs in size and form, particularly unfertilized Ascaris lumbricoides (38 to 45 m). The outline of this artifact is usually circular to oval, and it may or may not have a distinct cell wall. Plant material has hairs (pseudocilia) extending from its periphery and is often rough in texture. The cell’s interior resembles a tangled mess of odd-shaped vacuoles.

Epithelial Cells

The scale and structure of epithelial cells also resembles that of amebic trophozoites. Furthermore, epithelial cells, like amebic trophozoites, have a single nucleus and also have a separate cell wall. The internal structures of amebic trophozoites are not present in epithelial cells. The cytoplasm of epithelial cells, for example, is normally smooth and free of inclusions. The nucleus of a large epithelial cell, on the other hand, may be a large chromatin mass that looks like a nucleus.

Fungal Elements

Fungal elements may resemble protozoan cysts in size and form. This objects are readily distinguished from parasitic types by their lack of internal structures.

Starch Cells

Starch cells, also known as starch granules, are circular to irregular round shaped starch cells that measure less than 10 m and can appear at first glance to be protozoan cysts, especially those of E.hartmanni and E. nana (both measuring 5 to 12 m). Since they lack internal mechanisms, these cells can easily be separated from parasitic types. A nondescript mass within the cell that resembles a nucleus is often present. There are no karyosomes or peripheral chromatin in this structure, according to further investigation. Furthermore, starch cells can be distinguished from parasites by their iodine-stained dark blue black appearance.

Clumped or fused platelets

Platelets that clump or fuse on Giemsa-stained blood film smears, particularly the young trophozoite type, are often mistaken for malarial parasites. Clumped or fused platelets have a purple cytoplasm with a red chromatin, unlike malarial parasites, which have a blue cytoplasm with a red chromatin. Malaria parasites, in comparison to clumped or fused platelets, have a more detailed outline.

Stain precipitate

On a blood smear, Giemsa-stain precipitate can be observed and confused for malarial parasites. The stain precipitate is normally blue in color and differs in size and shape from malarial parasites.

Red Cell Abnormalities

On Giemsa-stained blood smears, defects of red blood cells such as HJ bodies or Cabot’s rings can be visible. The distinct staining properties of these anomalies will easily differentiate them from malarial parasites.

Further Reading: Images of some common artifacts and confusers can be found on CDC website.

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