Diagnosis of Autoimmune Diseases

Question 1

Sensitivity

Answer 1

The proportion of people who tested positive, out of everyone with the disease

Question 2

Sepcificity

Answer 2

The proportion of people who tested negative, out of everyone without the disease

Question 3

Positive predictive value

Answer 3

The proportion of people with the disease, out of everyone who tested positive

Question 4

Negative predictive value

Answer 4

The proportion of people without the disease, out of everyone who tested negative

Question 5

Non specific markers of systemic inflammation

Answer 5

CRP-produced acutely by liver in inflammation
ESR- viscocity of plasma increases in inflammatory response
Fibrinogen
Albumin decreases- liver is too busy
Complement decreases- complement factors consumed

Question 6

Antinuclear antibodies (ANA)

Answer 6

Attack nuclei of lymphocytes in patients with SLE. Sometimes found in patients with infection.

Question 7

2 specific types of ANA

Answer 7

Extractable nuclear antigens (ENA), or dsDNA

Question 8

Describe the sensitivity and specificity of the ANA test

Answer 8

High sensitivity, low specificiy- identifies everyone with SLE, but some identified in infection

Question 9

A test used to measure up to 20 autoimmune markers in a single serum sample

Answer 9

Multiplex assessment of non-organ specific autoantibody with a novel microbead-based immunoassay

Question 10

Rheumatoid Factor

Answer 10

Presents in RA. An autoantibody that targets the Fc region of IgG, but if too high, can precipitate, causing localised vasculitis or RA. Can also be seen in chronic infections.

Question 11

Anti CCP (ACPA)

Answer 11

more specific biomarker for RAB. Present in 95% patients with RA. Autoantibody against proteins released in cell death.

Question 12

The 2 types of Anti neutrophilic cytoplasmic antibodies (ANCA)

Answer 12

Cytoplasmic ANCA- target PR3 protein in cytoplasm

Perinuclear ANCA- target MPO protein in nucleus

Question 13

What propotion of people with systemic vasculitis are ANCA negative?

Answer 13

10-50%. It often still presents after the disease has subsided.

Question 14

Autoimmune biomarker for autoimmune liver disease

Answer 14

Anti-mitochondrial Abs for biliary sclerosis

Anti-smooth muscle and anti-liver/kidney/microsomal Abs found in autoimmune hepatitis

Question 15

Autoimmune biomarkers in type 1 diabetes

Answer 15

Islet cell Ab

Anti GAD65 and anti GAD67