Autoimmunity diagnosis

Question 1

Define Sensitivity

Answer 1

Measure of how good a test is in identifying people with the disease

Question 2

Define Specificity

Answer 2

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

Question 3

What are positive & negative predictive values?

Answer 3

\+ve= proportion of people with a positive test who have the target disorder
-ve= proportion of people with a negative test who do not have the target disorder

Question 4

What types of diagnostic tests are there?

Answer 4

• Non specific: inflammatory markers

- Disease specific: HLA typing, autoantibody testing

Question 5

Name some non-specific markers of systemic inflammation

Answer 5

• ESR
• CRP
• Ferritin
• Fibrinogen
• Haptoglobin
• Albumin
• Complement

Question 6

What is ANA?

Answer 6

• Antinuclear antibodies

- Detection by fluorescence

Question 7

What is rheumatoid factor?

Answer 7

• Antibody (IgM, IgG, IgA) directed against the Fc portion of IgG
• Commonly found in rheumatoid arthritis
• Not diagnostic of the diseases
• High titters may be pathogenic in vasculitis
• Can be seen with other diseases in which polyclonal stimulation of B cells is seen

Question 8

What is anti-CCP can any alternatives be used?

Answer 8

• Blood test
• ACPA more specific for RA then RF
• Similar sensitivity to RF
• Useful prognostic marker
• ACPA positive patients tend to have more severe erosive disease

Question 9

What does ANCA stand for?

Answer 9

Anti-Neutrophilic Cytoplasmic Antibodies

Question 10

Describe autoimmune liver disease

Answer 10

• Anti-mitochondrial Ab specific for primary biliary sclerosis
• Anti-smooth muscle & anti-liver/kidney/microsomal
• Abs found in autoimmune hepatitis
• Antibodies detected by IF screening & antigen specific ELISA

Question 11

What is autoantibodies in Type I diabetes mellitus?

Answer 11

• Non-pathogenic
• Several types: islet cell antibodies, anti-insulinoma antigen, anti-GAD(65, 67), insulin autoantibodies
• Disappear with progression of disease & total destruction of β islet cells

Question 12

What is the role of autoantibodies in diagnosis of type I diabetes mellitus?

Answer 12

• Disease conformation
• Identify relatives & patients at risk of developing autoimmune diabetes
• Negative predictive value ICA & IAA
• Inc risk of disease development with greater number of different autoantibodies present & younger age of patient

Question 13

What is the future of diagnostic testing in autoimmune diseases?

Answer 13

• Cytokines determination in serum
• Detection of antigen specific autoimmune T & B cells
• Measure of therapeutic response
• Personalised medicine, genetic profiling to determine individual risk of the disease