Different Types of Tests (Exam 1) Flashcards
What 3 types of tests are available to study body fluids?
1) Presumptive
2) Confirmatory
3) Species specificity
Is a presumptive test more or less sensitive than a confirmatory test?
More
What does a positive presumptive test indicate?
The possible presence of a body fluid in question
Can the presence of a stain be confirmed for certain by a presumptive test?
No
What happens if a presumptive test is negative?
Testing ends there as no substance of interest was found
What are the two types of presumptive tests?
1) Catalytic color
2) Chemiluminescence & fluorescence
What are the 2 most common catalytic color presumptive tests?
1) Phenolphthalein
2) Hemastix test strips
What is the key reagent in the Hemastix test strip?
Tetramethylbenzidine (TMB)
What are the 3 common fluorescence presumptive tests?
1) Alternate light source (ALS)
2) Luminol
3) Fluorescein
When should alternate light source be used?
For substances not visible to the naked eye
In what 2 ways are the chemiluminescence and fluorescence tests similar?
1) Used when blood is invisible i.e. faded/washed
2) Used when blood is in unconventional spot
What does a confirmatory test prove?
The presence of a particular body fluid in a questioned item
What does it mean if a confirmatory test is negative given that the presumptive test is positive?
There could be a false negative, especially when considering that confirmatory tests are not as sensitive as presumptive tests
What 2 things does a species specificity test prove?
The presence of a body fluid in a stain and what species it belongs to
Why could you possibly skip a species specificity test?
You might not have a lot of DNA
How do you determine if your sample is human when using a species specificity test?
Use the standard human DNA quantity, and if none of that comes back as human, then none of it is human
Blood & semen use the three types of serology tests, but saliva uses…
Salivary amylase enzyme
Is estimating the salivary amylase enzyme useful?
It isn’t common but MAY come in handy
In what 2 ways are the chemiluminescence and fluorescence tests different?
1) Fluorescence rxn lasts longer
2) Light is a natural product of chemiluminescence
What 2 aspects are blood group testing based on?
Antigens and antibodies