Diagnosis of autoimmune diseases

Question 1

define sensitivity

Answer 1

measure of how good is the test in identifying people with the disease 


Question 2

define specificity

Answer 2

measure of how good is the test at correctly defining people without the disease


Question 3

define positive predictive value.

Answer 3

The proportion of people with a positive test who have the target disorder


Question 4

define negative predictive value

Answer 4

The proportion of people with a negative test who do not have the target disorder.

Question 5

What are the 2 types of diagnostic test available

Answer 5

1- Non-specific.

2- Disease specific.

Question 6

What types of tests are included in non-specific markers

Answer 6

ESR- if inflammation, thicker blood results in longer sedimentation rate.
CRP-produced by liver in response to inflammation
Ferritin- level increase
Fibrinogen- level increase
Haptoglobin- level decrease (synthetic capacity of liver is reduced)
Albumin- level decrease (synthetic capacity of liver is reduced)
Complement- level decreases and CD3 and CD4 are actively used up

Question 7

What test follows a positive ANA.

Answer 7

ENA-extractable nuclear antigen.
• The 4-test ENA panel is used to help diagnose mixed connective tissue disease (MCTD), systemic lupus erythematosus (SLE), and Sjögren syndrome.
• The 6-test ENA panel can also help identify scleroderma (systemic sclerosis) and polymyositis/dermatomyositis (inflammatory

Question 8

How is a ANA test conducted

Answer 8

• Use fibroblast and expose cell nuclei
• Add serum of patient
• Primary reaction-antibody if present, attaches to the antigen
• Secondary reaction-secondary autoantibody, which has a fluorescence tag, is used to attaches to the antibody/antigen complex, which is formed.
• Detection of ANA does not mean that it is an autoimmune condition as it can be found in someone with flu

Question 9

What type of sensitivity and specificity is the ANA test

Answer 9

high sensitivity but low specificity.

Question 10

What type of sensitivity and specificity is the dsDNA (for lupus) and ENA

Answer 10

high specificity and low sensitivity.

Question 11

How is multiplex assessment of non-organs specific autoantiobodies with novel micro bead based immunoassays carried out

Answer 11

• Beads, present with internal colouring which can be identified by a detector.
• Antigen attached to bead
• Attack the bead with a specific antibody.
• Use a secondary antibody to show which antibodies have stuck to which antigens- has flurescence
• Measure 20-30 different antibodies with 1 serum test
• Disadvantage- doesn’t show autoantibodies for antigens, which aren’t tested.

Question 12

What conditions is Rheumatoid factor present in.

Answer 12

• Commonly found in rheumatoid arthritis but not diagnostic of the diseases
Can be preset in the flu.
• Can be seen with other diseases in which polyclonal stimulation of B cells is seen

Question 13

Is Anti-CCP (ACPA)- anti-cyclic citrullinated peptide more specific for rheumatoid arthritis than RF

Answer 13

Yes

• Specific to citrulline factor which presents in cell death from argilline.

Question 14

What condition does ANCA test for

Answer 14

Vasculitis.

Question 15

What are the 2 main types of ANCA which can be tested

Answer 15

cytoplasmic ANCA

Nuclear ANCA

Question 16

What condition does a positive test of anti- mitochondrial Ab

Answer 16

primary biliary sclerosis

Question 17

What condition does a positive test of anti- smooth muscle and anti-liver/kidney/microsomal (LKS) Abs

Answer 17

autoimmune hepatitis

Question 18

What are the autoantibodies for Type 1 diabetes.

Answer 18

–	islet cell antibodies					
–	anti-GAD65  anti-GAD67						
–	anti-insulinoma antigen 2 (IA-2)			
–	insulin autoantibodies (IAAs)
As condition progresses you get more and more autoantibodies to different things.