CP9 - Diagnosis of Autoimmune Diseases

Question 1

what is sensitivity?

Answer 1

measure of true positives

Question 2

what is specificity?

Answer 2

measure of true negatives

Question 3

what is positive predictive value?

Answer 3

proportion of people with a positive test who have the disorder

Question 4

what is a negative predictive value?

Answer 4

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

Question 5

what are the 2 types of diagnostic tests?

Answer 5

1. non specific eg. inflammatory markers
2. disease specific eg. autoantibody testing
   HLA typing

Question 6

what are the non-specific markers of systemic inflammation? (acute phase response proteins)

Answer 6

1. ESR
2. CRP - produced by the liver for an acute phase response, rapidly produced and used up
3. Ferretin
4. Fibrinogen
5. Haptoglobin
6. Albumin
7. Complement - useful when testing for systemic autoimmune disease

Question 7

what is ESR?

Answer 7

erythrocyte sedimentation rate is tested by putting blood in a very narrow capillary tube and testing for sedimentation rate. inflammation results in more aloof cells, making the plasma more viscous, therefore increasing the ESR

Question 8

how is the anti-nuclear antibody test useful?

Answer 8

a screening test which tells us if there are any autoantibodies against the nucleus in the circulation
sensitivity - 100%
specificity 60%, therefore only supports a clinical diagnosis

Question 9

how is the antinuclear antibody test conducted?

Answer 9

large fibrocyte cells are spread along microscopic slides, incubated with the patient’s serum.
any autoantibodies present will bin to them
a second set of antibodies with a fluorescent tag is use to bind to the autoantibodies

Question 10

what are ENAs?

Answer 10

extractable nuclear antigens. the next level of testing. more specific.

Question 11

what do autoantibodies target?

Answer 11

ribonucleoprotein, a substance which deals with DNA maintenance and transcription

Question 12

what is RF?

Answer 12

rheumatoid factor, used for the diagnosis of RA. we produce RF to target the Fc production of IgG. it is commonly found in RA but is not diagnostic of the disease.
it can also be observed in other diseases in which polyclonal stimulation of b cells is observed

Question 13

what is ACPA?

Answer 13

a biomarker which is more specific to RA than RF. test is useful if someone present with joint symptoms, picks up patients earlier. helps diagnose patients at pre-clinical and earl clinical stages
ACPA patients tend to have a more severe disease

Question 14

what is ANCA?

Answer 14

anti-neutrophilic cytoplasmic antibodies - used to pick up patients with inflammation of blood vessels

Question 15

what systemic vascularities does ANCA cause?

Answer 15

granulomatosis with polyangitis (wagerer’s granulomatosis)
microscopic polyangitis
charge-strauss syndrome

Question 16

what is the level of autoantibodies a direct indicator of?

Answer 16

how well the patient is responding to treatment, it is possible that the autoantibody disappears. re-emergence is a sign of relapse, and can start treating before they develop symptoms

Question 17

last few slides?

Answer 17

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