Immunology in Disease Diagnosis

Question 1

What is test specificity?

Answer 1

The ability of the test to correctly identify those without the condition/disease

Question 2

What is sensitivity?

Answer 2

The ability of a test to identify those with the condition

Question 3

What is the standard operating procedures?

Answer 3

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

Question 4

Where would you find standard operating procedures?

Answer 4

In things such as covid test - to do

Question 5

Why are controls used?

Answer 5

To know whether or not the test has been done correctly and if the positive or negative outcome is correct

Question 6

Do tests need to be reproducible?

Answer 6

Yes

Question 7

Do tests need to have health and safety guidelines?

Answer 7

Yes

Question 8

What type of sample collections would you do when running a test?

Answer 8

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

Question 9

What is non-invasive sample collection?

Answer 9

Urine, Faeces, Saliva, microbial cloud (microbes are shedded as you walk around (people you are with might have similar ones)), exhaled breath.

Question 10

What are types of invasive sample collection?

Answer 10

Throat swab and blood

Question 11

Why do you need baseline information?

Answer 11

Taken from the healthy population thats you can compare to people possibly with the disease

Question 12

What does direct observation provide?

Answer 12

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).

Question 13

What do you need to be careful about when taking blood samples?

Answer 13

You need to carefully break the skin and protect yourself and patients.

Question 14

Can microscopy diagnose patients? if so what is the accuracy of diagnosis determined by?

Answer 14

Yes

Reagents may be limited, electricity unreliable and based on the skill of the microscopist.

Question 15

What does indirect observation consist off?

Answer 15

Utilising humoral immunity - serology

Utilising cell mediated immunity - Cytokine, interferon gamma releasing assays, skin tests

Question 16

What does specificity in antibodies mean?

Answer 16

Degree to which is immune response descriminates against antigenic variants

Question 17

What are the 2 ways you can use antibodies?

Answer 17

Provides information on history of exposure

Can use commercially produced antibodies to detect for an antigen in a patients blood

Question 18

How does an indirect ELISA work?

Answer 18

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).

Question 19

How would you validate the assay?

Answer 19

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.

Question 20

What are the considerations of an ELISA?

Answer 20

False negative or positive

Due to non-specific binding or cross recognition or delay in immune response

Question 21

What are some wider consideration of ELISA’s?

Answer 21

They take time
Appropraite containment
Diagnostic capacity

Question 22

What are rapid diagnostic tests?

Answer 22

Cheap, quick, reliable, easy to use and interpret, stable under extreme conditions.

Such as HIV, malaria, syphilis, Hep B etc

Question 23

What are pro’s and cons of rapid tests?

Answer 23

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

Question 24

What is one way we could make rapid diagnostic tests better?

Answer 24

Limitation of waste
Safe disposable
Supply and demand

Question 25

Are you looking at the history or infection or antigen in covid tests - why?

Answer 25

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.

Question 26

Are covid tests reliable, how is the sample taken?

Answer 26

Yes they are

Invasively - back if the nose

Question 27

How do the covid tests work?

Answer 27

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.

Question 28

How does the covid test work if you have covid or not?

Answer 28

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.

Question 29

Malaria - how is this common diagnosed?

Answer 29

Microscopy

Question 30

How does the malaria rapid test work?

Answer 30

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).

Question 31

Can some malaria give you two postitive lines on a test and if so why?

Answer 31

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