9 - Diagnosis of autoimmune diseases Flashcards

1
Q

Sensitivity definition

A

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

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2
Q

Specificity definition

A

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

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3
Q

Positive predictive value

A

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

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4
Q

Negative predictive value

A

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

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5
Q

Type of autoimmune diagnostic tests

A

Non-specific = inflammatory markers

Disease specific = autoantibody testing, HLA typing

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6
Q

I have ignored the following slides

A

8-17

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7
Q

What is rheumatoid factor?

A

Antibody (IgM, G, A) directed against the Fc portion of IgG.

Commonly found in rheumatoid arthritis but not diagnostic of disease (70% sensitivity and specificity)

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8
Q

What does ACPA stand for?

A

Anti-CCP

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9
Q

What does ACPA do?

A

ACPA more specific for rheumatoid arthritis (95%) than rheumatoid factor

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10
Q

What does ANCA stand for?

A

Anti-neutrophilic cytoplasmic antibodies

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11
Q

What is ANCA specific for?

A

Wegener’s granulomatosis

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12
Q

Cytoplasmic ANCA vs perinuclear ANCA

A

Target antigens - 90% PR3 for cANCA; 70% MPO for pANCA

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13
Q

What is the usefulness of ANCA testing?

A

Positive ANCA is extremely useful for diagnosis
Histopathology remains gold standard for diagnosis
Reemergence of ANCA pos in a ANCA neg whilst in remission suggests a risk of disease flare however correlation is poor.

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14
Q

What signs would you see in autoimmune liver disease?

A

Anti-mitochondrial Ab specific for primary biliary sclerosis

Anti-smooth muscle Ab

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15
Q

What autoantibodies in DMT1?

A

Non-pathogenic
Several types: islet cell Ab, anti-GAD65, anti-insulinoma antigen 2, insulin autoantibodies

Disappear with progression of disease and destruction of B islet cells

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16
Q

Role of autoantibodies in DMT1

A

Negative predictive value of Islet cell Ab and Insulin autoantibodies is 99%