Immunology in Disease Diagnosis Flashcards
What is test specificity?
The ability of the test to correctly identify those without the condition/disease
What is sensitivity?
The ability of a test to identify those with the condition
What is the standard operating procedures?
These are instructions on how to carry out the test in a consistent manner, so that the test provides a reliable outcome that can be compared against other findings in different or similar settings
Where would you find standard operating procedures?
In things such as covid test - to do
Why are controls used?
To know whether or not the test has been done correctly and if the positive or negative outcome is correct
Do tests need to be reproducible?
Yes
Do tests need to have health and safety guidelines?
Yes
What type of sample collections would you do when running a test?
Information from the appropriate site e.g this could be related to mode of transmission of infectious conditions, or how this acts on the body
What is non-invasive sample collection?
Urine, Faeces, Saliva, microbial cloud (microbes are shedded as you walk around (people you are with might have similar ones)), exhaled breath.
What are types of invasive sample collection?
Throat swab and blood
Why do you need baseline information?
Taken from the healthy population thats you can compare to people possibly with the disease
What does direct observation provide?
Tangible evidence, but this is not binary (just because you don’t see it doesnt mean it isn’t there but if you do then it means it is).
What do you need to be careful about when taking blood samples?
You need to carefully break the skin and protect yourself and patients.
Can microscopy diagnose patients? if so what is the accuracy of diagnosis determined by?
Yes
Reagents may be limited, electricity unreliable and based on the skill of the microscopist.
What does indirect observation consist off?
Utilising humoral immunity - serology
Utilising cell mediated immunity - Cytokine, interferon gamma releasing assays, skin tests
What does specificity in antibodies mean?
Degree to which is immune response descriminates against antigenic variants
What are the 2 ways you can use antibodies?
Provides information on history of exposure
Can use commercially produced antibodies to detect for an antigen in a patients blood
How does an indirect ELISA work?
An antigen of interest is put in a plate.
Add host serum and if they have this disease they will have antibodies and these will bind.
Then add an anti-human antibody which has an enzyme bound to it which will cause a colour change if correct reagent is added. This will bind to the patients antibody (this has to be highly specific).
How would you validate the assay?
Use controls and compare the colour of your sample to the positive and negative wells. Sometimes it will be clear with the colour change however if it is not (e.g. slightly lighter darker etc) then get the patients back in a few weeks after the disease has progressed a bit (unless its deadly) and the antibodies will increase if they have the disease.
What are the considerations of an ELISA?
False negative or positive
Due to non-specific binding or cross recognition or delay in immune response
What are some wider consideration of ELISA’s?
They take time
Appropraite containment
Diagnostic capacity
What are rapid diagnostic tests?
Cheap, quick, reliable, easy to use and interpret, stable under extreme conditions.
Such as HIV, malaria, syphilis, Hep B etc
What are pro’s and cons of rapid tests?
Pros - limited waste, empower user, tangible outcome
Con - management of outcome (only one person knows about it - you and you might not want to do anything about it) and duty of care
What is one way we could make rapid diagnostic tests better?
Limitation of waste
Safe disposable
Supply and demand
Are you looking at the history or infection or antigen in covid tests - why?
Antigen as most people have had covid more than once and so it would be pointless to look at antibodies as most people has it.
Are covid tests reliable, how is the sample taken?
Yes they are
Invasively - back if the nose
How do the covid tests work?
Once sample is mixed with antibodies (the buffer) and dropped on sample pad it is moved down the the test using capillary movement until it hits the absorbent pad. On its way it crosses the T antibody and the C antibody.
How does the covid test work if you have covid or not?
If you have covid the antigen and antibody binds and goes through test before binding to the second antibody at the T. The sample then continues down the test and the C antibody binds to unbound antibodies from the buffer.
If you dont have covid the unbound antibodies (anti-covid antibody) bind to C and nothing binds to T.
Malaria - how is this common diagnosed?
Microscopy
How does the malaria rapid test work?
Mix blood with antibodies in buffer and put in well B and A. This will travel along test using capillary action and if there is an antigen antibody mix it will bind to Antibody on T1 or T2 and the unbound antibody will bind to the antibody on C.
The two wells and T1 and T2 (sometimes even T3) is because there is two different malaria parasites (this means there will be two seperate buffers with antibodies).
Can some malaria give you two postitive lines on a test and if so why?
Yes as it can tell you if someone has the disease and if someone has a response to deletions (HRP-2) commonly found in malaria
