DIagnostic Methods Flashcards
Why is PCR for diagnosis of dermatophytosis not confirm active infection?
PCR detection of dermatophyte DNA can be helpful, however a positive PCR does not necessarily indicateactive infection, as dead fungal organisms from a successfully treated infection will still be detected on PCR, as will non-infected fomite carriers.
Negative PCR in a treated cat is compatible with cure. Negative fungal culture from a cat with no lesions and a negative Wood’s lamp (except for glowing tips) is compatible with cure
What is the fluorescence length of Wood’s lamp?
It is transparent in the violet/
ultraviolet band between 320 and 400 nm with a peak at 365 nm and a broad range of infrared and the longest, least visible red wavelengths
The original glass filter material has been replaced by newer materials (e.g. barium-sodium-silicate glass incorporating 9% nickel oxide) that coat the inside of glasstubes.
What causes the fluorescence of hair shafts under Wood’s lamp?
The characteristic green fluorescence observed on M. canis-infected hair shafts is due to a water-soluble chemical metabolite (pteridine) located within the cortex or medulla of the hair. The fluorescence is due to a chemical interaction that occurs as a result of the infection and is not associated with spores or infective material.
How do you test for D-Dimers in a vasculitis case?
A monoclonal antibody-based assay is available to detect D-dimers in the blood. Using a cutoff of greater than 500 ng/ml - there was a specificity of 100% and sensitivity of 64%.
Congo Red is used to stain for what in histopathologic sections?
Staining with Congo Red (CR) is a qualitative method used for the identification of amyloids in vitro and in tissue sections.
CD3
T cells (alpha-beta and gamma-delta)
CD79a
B cell (component of B cell antigen receptor) Minimally expressed in plasma cells
CD20
B cells (regulates B cell activation /proliferation) Not expressed in plasma cells
CD18
All leukocytes
Histiocyte marker in combination with CD3 and CD79a
CD90 (Thy-1)
Interstitial dendritic cells
NOT expressed by Langerhans cells
c-Kit
Mast cells (and hematopoietic progenitor cells)
E-cadherin
Langerhans cells (used to indicate cutaneous histiocytoma) Also expressed by epithelial cells and some leukocytes
Granzyme B
A serine protease most commonly found in the granules of natural killer cells (NK cells) and cytotoxic T cells.
CD8+ T cells and NK cells
Ki67
Cell proliferation marker (determines growth fraction of cell population)
MUM1/IRF4
Plasma cell marker (transcription factor)
Melan-A
Melanoma indicator
Pancytokeratin
Marker for squamous cell carcinoma
Myeloperoxidase (MPO)
Neutrophils and monocytes (lysosomal protein stored in granules)
Ziehl-Neelson Stain
Acid Fast Bacteria = RED
Masson Trichrome
Mature Collagen = Blue
Immature collagen, keratin, muscle and nerves = Red
Oil red O
Lipids = Red
Verhoeff’s Stain
Elastin and Nuclei = Black
Sudan Black B
Lipids = Green or Black
Periodic Acid-Schiff (PAS)
Fungi, glycogen, mucopolysaccharides and tissue debris = Red
Alcian Blue
Acid mucopolysaccharides = Blue
Toluidine Blue
Acid mucopolysaccharide and mast cell granules = purple
Gomori’sMethenamine Silver (GMS)
Fungi and melanin = Black
Gram Stain
Gram positive = Purple/Blue
Gram negative bacteria = Red (Safranin)
Brown-Brenn Stain
Gram positive = Purple/Blue
Gram negative bacteria = Red (Safranin)
Fite’s Modified Acid-Fast Stain
Acid Fast Bacteria = Red
Ziehl-Neelson Stain
Acid Fast Bacteria = Red
Giemsa Stain
Granules = Basophilic (important for mast cell ID)
Organisms = Basophilic (Differentiates it from GMS-Positive Histoplasmosis)
Most blood cells show red/pink cytoplasm and blue-purple nucleus.
Luna Stain
The most popular specific staining technique for eosinophils
What stain is effective in visualizing the Cryptococcus capsule?
Mayer mucicarmine is a useful special stain because it stains the organisms capsule red.
GMS, AS and Fontana will also work.
CD 1 (a,b,c)
Langerhans’ cells, dendritic cells
CD3
T cells (differentiates between B and T cell lymphoma)
CD4
Helper T cells, activated dendritic cells
CD11b
Myeloid cells (macrophages), NK cells
CD11c
Dendritic cells, NK Cells
CD11d
Macrophages identified in the splenic red pulp and bone marrow
CD18
Broad staining of leukocytes (prominent in histiocytic tumors)
CD45RA
B cells and naïve T cells
CD79a
B cells, (differentiate between B and T cell lymphoma)
MHC II
Broad expression in cells functioning in antigen presentation
Thy-1 (CD90)
CD34+ hematopoietic cells (specifically interstitial dendritic cells)
E-cadherin
Specific to epidermal Langerhans cells, epithelial cells
Vimentin
Mesenchymal cells
CD25
IL-2 receptor
What is the IHC for macrophages?
CD45, CD18, CD11b, MHCII, CD68
What is the IHC for APC dendritic cell?
CD45, CD18, CD1, CD11c, MHCII, CD11b, ICAM-1
What is the IHC marker for LC?
E-cadherin
Interstitial (dermal) DC
CD90
Activated dermal DC
CD4
Fontana-Masson
Premelanin and melanin – black (hemosiderin can be positive too, but less intense)
Giemsa (Wright-Giemsa)
Metachromatic staining of mast cell granules; may also help demonstrate donnovan bodies & Leishmania; parasites.
Donovan bodies are rod-shaped, oval organisms that can be seen in the cytoplasm of mononuclear phagocytes or histiocytes in tissue samples from patients with granuloma inguinale. They appear deep purple when stained with Wright’s stain.
Van Gieson’s
Mature collagen – red
Immature collagen, keratin, muscle, and nerves – yellow
Warthin–Starry stain (WS)
Used for the visualization of spirochetes but also for the detection of Helicobacter pylori and microsperediates. This stain is also used to confirm the presence of Bartonella henselae, the microorganism responsible for cat scratch disease.
Spirochetes are argyrophilic, that is to say they absorb the silver contained in a solution, but it is necessary to add a reducing agent in the solution to reduce the silver absorbed silver which will form silver. deposits and thus a coloring.
What is Gimenez stain used to identify?
Rocky Mountain Spotted Fever
What is the difference between Kinyoun and ZN stain?
The fundamental difference between the two carbolfuchsin-based methods is whether heat is used during the primary staining process. The Ziehl-Neelsen method uses heat to infuse the carbolfuchsin into the acid-fast cells, whereas the Kinyoun method does not use heat.
What is the best stain for Atypical mycobacterium and Leprosy?
Though modified Fite-faraco is more sensitive than Ziehl Neelsen method in detection of Mycobacterium leprae in tissue sections, it is tedious, time consuming and leads to observer fatigue.
CD45
is used as a marker of all hematopoietic cells (blood cells), except for mature erythrocytes (red blood cells) and platelets.
IBA1
that is specifically expressed in macrophages / microglia and is upregulated during the activation of these cells. Iba1 expression is up-regulated in microglia following nerve injury, central nervous system ischemia, and several other brain diseases.
Von Kossa
widely used in histology to detect the presence of abnormal calcium deposits in the body. The principle of this coloration is based on the transformation of calcium salts into silver salts: calcium ions, bound to phosphates, are replaced by silver ions brought by a solution of silver nitrate.
Summary of Stains
Toluidine blue: acid mucopolysaccarides and mast cells - purple
Gomori Methenamine silver: fungi and melanin - black
Periodic Acid-Schiff: neutral mucopolysaccarides, fungi - red
Ziehl-Nielson/Acid Fact: lipochrome, lipid walls of mycobacterium - red/pink
Von Kossa: calcium deposition - dark bue/purple
Oil-Red O: lipids - dark red
Mayer’s Mucicarmine: mucin and capsule of cryptococcus - red/pink
India Ink Stain
India ink capsule stain is used to demonstrate cell capsules through microscopic examination. This procedure is used to detect presence of encapsualted species, e.g. Cryptococcus neoformans, which causes cryptococcosis in humans.
