Blood Detection and Enhancement Flashcards
Give examples of presumptive tests.
Hemastix
Hemident
Hexagon OBTI
Kastle Meyer test
Describe Hemastix.
3’ plastic strips with a reagent material at the tip
How does the Hemastix reaction work?
Reagent at tip detects the peroxide-like activity of hemoglobin
What happens when Hemastix detects hemoglobin?
Tip turns green
What is a limitation of Hemastix?
Cannot differentiate between human and animal blood
Describe Hemident.
Disposable tube containing two chemical reagent ampoules
Swab of stain is placed inside tube and both ampoules are broken
What is an indication of blood in Hemident?
Blue/green reaction
What is a limitation of Hemident?
Does not distinguish between human and animal blood
What is another name for Hemident?
McPhail’s Reagent
Describe how Hexagon OBTI works.
Swab added into transport medium
Medium added to test bar
What does two lines mean in Hexagon OBTI?
Human origin
Up to how much dilution can Hexagon OBTI detect blood?
1:1,000,000
How many red blood cells are required for a positive Hexagon OBTI result?
As few as 500 RBCs required
What is another name for the Kastle Meyer test?
Phenolphthalein
Outline the 3 solution process of the Kastle Meyer test.
Moistent swab with solution A
Swab stain
Add 1-2 drops of Sol B (Phenolphthalein)
Add 1-2 drops of Sol C (hydrogen peroxide solution)
Describe what an inconclusive Kastle-Meyer result would look like.
Delayed reaction (takes more than 30 seconds)
Swab turns pink before addition of the hydrogen peroxide solution
Describe what a positive Kastle Meyer result would look like.
Swab turns pink after the addition of the peroxide solution
Describe what a negative Kastle Meyer test would look like.
No pink colour change
No reaction after addition of peroxide solution
What is a limitation of the Kastle Meyer test?
Not specific for blood; some materials can give false positives
Give exmaples of material that can lead to a false positive in the Kastle Meyer test.
Plant matter (ex. broccoli, horseradish, potatoes)
Bleach
Some soaps and disinfectants
Rust or metal oxides
Some adhesives and glues
What is done after a presumptive blood test?
Confirmatory testing - swabs are sent to CFS for analysis.
Differentiate between blood dectection and enhancement.
Detection of blood is finding that blood is present.
Enhancement is the act of increasing its visibility.
What factors should be considered when detecting or enhancing blood?
3
Necessity
Health and safety
Interference with other examinations
List some things to be considered when deciding if blood enhancement and/or detection is necessary.
5
What is that stain?
Is it already visible/detectable as is?
What is the best option?
What benefit can be achieved by doing it?
Preference or direction from BPA ANalyst
What should be considered in terms of the health and safety of blood enhancement/detection?
5
Is it carcinogenic?
What PPE is required?
Does the area require evacuation?
Is it flammable?
Clean up
What should be considered when determining if a blood detection/enhancement method will interfere with other examinations?
5
Where are you going to do this?
How can that be achieved?
What potential interference can occur?
Will it affect the stain?
Dilution
List blood detection and enhancement methods from least to most destructive.
Visual (available light)
Visual (white light, ALS, laser)
Blood locaters and enhancers
When are enhancement chemicals used?
When there is visible blood and some type of pattern is suspected.
How do enhancement chemicals work? Are they blood specific?
They stain the protein component of blood, not specific for blood
Are enhancement chemicals considered presumptive testds?
No
What must be collected before blood is enhanced?
3
Photos
DNA samples
Presumptive test
List the enhancement chemicals discussed in class.
6
Hungarian red
Acid yellow
Amido black
Coomassie Blue
LCV
LMG
What type of stain is Hungarian Red?
Protein stain
On what type of surfaces is Hungarian Red suitable for blood enhancement?
Non-porous surfacs
What colour of staining does Hungarian Red result in?
Red/purple stain
What are the 3 steps for Hungarian Red enhancement?
Fixative
Dye application
Rinse
Can Hungarian Red be lifted? If so, with what?
Can be lifted with gel lifter
Describe how Hungarian red fluoresces.
Can fluoresce with green light (505-530 and red filter)
What kind of stain is Acid Yellow?
Protein stain
On what type of surfaces is acid yellow suitable?
Non-porous surfaces
What colour stain is produced by Acid Yellow?
Yellow stain
Does acid yellow require an ALS?
Yes
Outline the 3 steps for enhancement with acid yellow
Fixative
Dye application
Rinse
Describe ALS requirements for acid yellow
Fluoresces with blue (450 nm) light and orange filter
What type of stain is amido black?
Protein stain
On what type of surfaces is amido black suitable?
Porous or non-porous surfaces
What colour does amido black produce?
Blue-black colour
What are the three steps for amido black enhancement?
Fixative
Dye application
Rinse
What should be kept in mind about amido black?
May stain surfaces
Does amido black require ALS?
No
What kind of stain is Coomassie Blue?
Protein stain
On what type of surfaces is Coomassie Blue suitable?
Porous and non-porous
What stain results from Coomassie Blue?
Blue stain
Does Coomassie Blue require an ALS?
No
Outline the process of Coomassie Blue enhancement
Dip or spray with reagent
Rinse with provided rinse
What fixative is used if water is the main solvent in the dye?
5-sulphosalicylic acid
What fixative is used if methanol is the main solvent in the dye?
Methanol
What is the purpose of the rinse on non-porous surfaces?
Removes excess dye
What is the purpose of the rinse on porous surfaces?
Destainer
How does leucocrystal violet work?
Reacts with heme in red blood cells
On what type of surfaces is LCV suitable?
Porous or non-porous
How is LCV applied?
SPray
What colour is produced by LCV?
Purple/violet
Describe how the LCV reaction progresses/
Oxidation occurs slowly with influence of light, development is not permanent and background can also develop over time
What colour is produced by leucomalachite green?
Green
List the search chemicals for blood detection.
3
Luminol
Bluestar
LCV
How does luminol work?
Iron in blood catalyzes luminescence
What is the purpose of luminol?
FInd traces of blood even if someone has attempted to clean or remove
How is luminol applied?
SPray
True or false: Luminol can be used in the light and the dark.
Flase, needs to be done in darkness
How long does the blue glow of luminol last?
30 seconds
How is the effects of luminol documented?
Long-exposure
What is an important consideraiton for luminol?
Tends to lose fine detail
Compare Bluestar to Luminol.
Based on Luminol but requires no chemical mixing
How is Bluestar prepared?
Tablets dissolved in water
How does Bluestar work?
Reacts with heme in red blood cells
How is Bluestar applied?
Spray
What is an important consideration for Bluestae?
Tends to lose fine detail
What materials can give false positives for Luminol and Bluestar?
4
Plant peroxidases
Chemical oxidants
Certain cleaning materials
Metals
Does Bluestar require complete darkness?
No
What happens to luminescence during second application of Luminol? Bluestar?
Diminished in luminol, maintained in Bluestae
Are Luminol and Bluestar DNA destructive?
No
What is the shelf life of Luminol after mixing?
None
What is the shelf life of Bluestar after mixing?
Can be used for several days
Is laboratory preparation needed for Luminol?
Yes
Describe how to photograph Luminol and Bluestar.
3
Tripod
Photograph in ambient light, darken room and do not move camera
Overlay photographs
