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Y2 Clinical Pathology > Diagnosis of Autoimmune Conditions > Flashcards

Diagnosis of Autoimmune Conditions Flashcards

1
Q

What is the process behind why an autoimmune disease develops?

A

The immune system should be tolerant to self antigens

i.e. Not identify them as something that needs to be attacked

any part of the immune system that could attack self antigens should be eliminated

if it is not eliminated, then autoimmune disease results

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2
Q

What types of tests are needed to identify autoimmune diseases?

A

Tests are needed to detect which autoantibodies are present in the patient’s blood

various laboratory techniques are used to identify these antibodies

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3
Q

What are the stages in working out which autoimmune disease that a patient has?

Why is it important to achieve the correct diagnosis?

A
  1. Take the clinical history
  2. Examine the patient
  3. Perform some blood tests

different autoimmune diseases can have similar symptoms

acheiving the correct diagnosis leads to correct management

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4
Q

What is sclerodactyly?

A

localized thickening and tightness of the skin of the fingers or toes

it often leads to ulceration of the skin of the distal digits

It is often accompanied by atrophy of the underlying soft tissues

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5
Q

What is livedo reticularis?

A

Mottled reticulated vascular pattern that appears as a lace-like purple discolouration of the skin

it is caused by swelling of the venules, leading to construction of the capillaries by small blood clots

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6
Q

What is scleroderma (diffuse systemic sclerosis)?

A

Chronic autoimmune condition that affects the skin, connective tissue and internal organs

It results in hard, thickened areas of skin and sometimes problems with internal organs and blood vessels

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7
Q

What is scleroderma caused by?

A

the immune system attacking the connective tissue under the skin and around internal organs and blood vessels

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8
Q

What tests would be performed to confirm diagnosis of scleroderma?

A

ANA

ANCA

CK

Rheumatoid factor

Anti-CCP antibody

Complement

FBC, U&Es, LFTs, CRP

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9
Q

Why are diagnostic tests performed?

A

They are used to answer specific questions and/or to support a clinical diagnosis

They are NOT used as screening tools

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10
Q

What can improve the ability of the tests to distinguish between health and disease?

A

The ability of the tests to correctly discriminate between health and disease is improved when they are used in the appropriate population

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11
Q

What is meant by sensitivity?

A

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

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12
Q

How is sensitivity worked out from this table?

A

[a / (a+c)]

a = true positive

b = false positive

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13
Q

What is meant by specificity?

A

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

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14
Q

How is specificity worked out from this table?

A

[d / (b + d)]

b = false positive

d = true negative

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15
Q

What is meant by positive predictive value?

A

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

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16
Q

How is positive predictive value worked out from this table?

A

[a / ( a + b )]

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17
Q

What is meant by negative predictive value?

A

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

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18
Q

How is negative predictive value worked out from this table?

A

[d / (c + d )]

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19
Q

What are the missing labels regarding testing

A
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20
Q

What are the 2 types of diagnostic tests?

A

Non-specific:

  • inflammatory markers

Disease specific:

  • autoantibody testing
  • HLA typing
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21
Q

What are the non-specific markers of systemic inflammation?

A
  1. ESR
  2. CRP
  3. Ferritin
  4. Fibrinogen
  5. Haptoglobin
  6. Albumin
  7. Complement
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22
Q

What are antinuclear antibodies (ANA)?

A

Antibodies in the patient’s blood that bind to the cell nucleus

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23
Q

How can antinuclear antibody testing (ANA) be made more specific?

A

By identifying subtypes of antibody that bind to different bits of the cell nucleus

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24
Q

How is the ANA test performed?

A
  1. A blood sample is taken from the patient’s arm
  2. An ANA test is performed by testing the blood in the laboratory
  3. The antibodies in the serum of the blood are exposed in the laboratory to cells
  4. It is then determined whether are not antibodies are present that react to various parts of the nucleus of cells

Fluroescent techniques are used to detect the antibodies in the cells

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25
What does a positive ANA test suggest?
That an autoimmune disease is present This does not make a specific diagnosis, it just suggests that some form of autoimmune disease is present
26
What is meant by the detection of DSDNA and ENAs?
Anti dsDNA is a type of antinuclear antibody that is present in SLE Extractable nuclear antigens (ENAs) An ENA panel tests for autoantibodies against 6 or 7 proteins in the cell nucleus
27
What technique is used in detection of ENAs?
**Immunoblots** this technique involves the detection of specific proteins in a sample of tissue to homogenate or extract antbodies with fluorescent tags are used to identify specific proteins
28
What does ELISA stand for? What is this test used for?
Enzyme-linked immunosorbent assay An antigen is immobilised on a solid surface and then complexed with an antibody that is linked to an enzyme detection of a specific protein is accomplished through assessing the conjugated enzyme activity
29
What other method can be used for antinuclear autoantibody assessment?
**Microbead-based immunoassay**
30
What autoantibodies are present in the following conditions: i. SLE ii. Sjögren's syndrome iii. Neonatal lupus erythrematosis iv. Diffuse systemic sclerosis v. limited systemic sclerosis
31
I dsDNA, Sm ii. La iii. Ro iv. Scl-70 v. Centromere
32
What auto-antibodies are present in the following conditions? i. Polymyositis ii. Dermatomyositis iii. Rheumatoid arthritis
I. Jo-I ii. Mi-2 iii. CCP
33
Which autoantibodies are seen in the following conditions? i. Diffuse glomerulonephritis ii. Membranous glomerulonephritis iii. Neonatal heart block
I dsDNA - SLE with kidney disease ii. Sm, Ro - SLE with kidney disease iii. Ro - maternal antibody
34
Which autoantibodies are present in the following conditions? i. Raynaud's phenomenon ii. Fibrosis alveolitis iii. Erosive joint damage
I. U1-RNP as part of overlap syndromes ii. Jo-1 (in polymyositis), U1-RNP iii. CCP - in RA and overlap syndromes
35
What is alopecia?
"Spot alopecia" a condition in which hair is lost from some or all areas of the body It often results in a few bald spots on the scalp
36
What would the complement blood results look like in someone with SLE? What about ANA by indirect immunofluorescence?
C4 and C3 will be low ANA shows a positive, homogenous pattern
37
What is the tool used for diagnosing SLE?
American College of Rheumatology Diagnostic Criteria There are both **clinical criteria** and **immunologic criteria** The requirements are \>/= 4 criteria (at least 1 clinical and 1 laboratory criteria) or a biopsy-proven lupus nephritis with positive ANA or anti-DNA
38
What is rheumatoid factor?
An antibody (IgM, IgG or IgA) directed against the FC portion of IgG
39
What types of diseases is rheumatoid factor associated with?
It is commonly found in **rheumatoid arthritis** but is not diagnostic of the diseases It can be seen in other diseases in which **polyclonal stimulation of B cells** is seen e.g. chronic infections
40
When is Anti-CCP antibody (ACPA) used as a diagnostic tool? How sensitive is it?
It is more specific for rheumatoid arthritis than RF It has similar sensitivity to RF It is a useful prognostic marker - ACPA positive patients tend to have **more severe and erosive disease**
41
What would a joint X ray look like in rheumatoid arthritis?
Peri-articular swelling with effusion of MCP joints osteopenia joint space narrowing and erosions
42
What types of blood test results would be seen in rheumatoid arthritis? Why is early treatment important?
High rheumatoid factor, CCP and elevated ESR and CRP add to the probability of a definitive diagnosis Early treatment can prevent joint damage and significant morbidity
43
When are anti-neutrophilic cytoplasmic antibodies (ANCA) ordered?
They are ordered when **vasculitis** is queried e.g. renal or ENT
44
What are the symptoms of **granulomatosis with polyangitis ?**
**Oral cavity:** * ulceration throughout oral mucosa **Lungs:** * cavities * bleeds * lung infiltrates **Skin:** * nodules on the elbows * purpura **Eye:** * pseudotumours * conjunctivitis **Nose:** * stuffiness * nosebleeds * saddle nose **Heart:** * pericarditis **Kidneys:** * ​glomerulonephritis
45
What are the symptoms of granulomatosis with polyangitis caused by? What test is positive in this condition?
Granulomas and patchy necrosis in blood vessels there would be a positive anti-neutrophil cytoplasm test
46
What is the difference between cytoplasmic (c) ANCA and perinuclear (p) ANCA?
**Cytoplasmic ANCA:** * Granular fluorescence of neutrophil cytoplasm with nuclear sparing **Perinuclear ANCA:** * ​apparent fluorescence of the nucleus only
47
What is the difference between ANCA and anti-PR3/MPO?
ANCA is the pattern anti-PR3/MPO is the autoantibody causing the condition
48
What are the target antigens for cytoplasmic and perinuclear ANCA?
**Cytoplasmic ANCA:** * PR3 - 90% * MPO **Perinuclear ANCA:** * MPO - 70% * PR3
49
What are the symptoms and features of granulomatosis with polyangitis? (Wegener's cANCA anti-PR3 positive)
**Histology:** * leukocytoklastic vasculitis * necrotising, granulomatous inflammation **ENT:** * nasal septum perforation * saddle nose deformity * conductive or sensorineural hearing loss * subglottic stenosis **Eye:** * orbital pseudotumours * scleritis * episcleritis * uveitis (50%) **Lung:** * nodules * infiltrates or cavitary lesions * alveoral haemorrhage **Kidney:** * segmental necrotising glomerulonephritis **Heart:** * occasional valvular lesion **Peripheral nerves:** * vascultic neuropathy (58%) **Eosinophilia:** * occasional eosinophilia
50
What are the signs and symptoms of microscopic polyangitis? pANCA anti MPO positive
**Histology:** * leukocytoklastic vasculitis * granulomatous inflammation **ENT:** * Absent or mild **Eye:** * Occasional eye disease * scleritis * episcleritis * uveitis **Lung:** * alveolar haemorrhage **Kidney:** * ​segmental necrotising glomerulonephritis **Heart:** * rare **Peripheral nerves:** * vasculitic neuropathy **Eosinophilia:** * none
51
What are the signs and symptoms of Churg-Strauss syndrome?
**Histology:** * eosinophilic tissue infiltrates and vasculitis * granulomas have eosinophilic necrosis **ENT:** * nasal polyps * allergic rhinitis * conductive hearing loss * **Eye:** * occasional eye disease * scleritis * episcleritis * uveitis **Lung:** * Asthma * fleeting infiltrates * alveolar haemorrhages **Kidney:** * segmental necrotising glomerulonephritis (rare) **Heart:** * heart failure **Peripheral nerves:** * vasculitic neuropathy **Eosinophilia:** * all
52
Complete the table for the clinical utility of ANCA testing?
53
What is the clinical utility of a positive ANCA test?
* Useful in suggesting the diagnosis in the proper clinical setting * histopathology remains the gold standard for diagnosis in most cases
54
What do negative ANCA assays not exclude?
Negative ANCA assays do not exclude AASV 10-50% of patients may be ANCA negative
55
What does persistence of ANCA in the absence of clinical indications suggest?
Persistence of ANCA in the absence of clinical indications of active disease **_DOES NOT_** indicate a need for continued treatment
56
What does reemergence of ANCA positive in a patient who was ANCA negative whilst in remission suggest?
A risk of **disease flare** the time to the flare is uncertain
57
How is autoimmune liver disease screened for? Why may it be screened for?
It is part of the non-invasive liver screen that is performed if liver tests are deranged Antibodies are detected by IF screening using rodent tissue block (oesophagus, liver and kidney) and antigen-specific ELISA
58
What is looked for in the autoimmune liver disease screen for **primary biliary sclerosis** and **autoimmune hepatitis**?
**Primary biliary sclerosis:** * anti-mitochondrial antibody that is specific for PBS **Autoimmune hepatitis:** * anti-smooth muscle and anti-liver/kidney/microsomal (LKS) antibodies
59
What are the different types of autoantibodies in type 1 diabetes mellitus?
1. Islet cell antibodies 2. Anti-GAD65 and anti-GAD67 3. Anti-insulinoma antigen 2 (IA-2) 4. Insulin autoantibodies (IAA)
60
What happens to the autoantibodies in type 1 DM with time?
They disappear with progression of disease and total destruction of B-islet cells
61
Why do we test for the autoantibodies in type 1 DM?
To confirm presence of the disease to identify relatives and patients at risk of developing autoimmune diabetes
62
What happens in Addison's disease? Which autoantibodies can be detected?
There are clinical features as it impairs production of cortisol you can detect autoantibodies targeting the **adrenal cortex**
63
What antigen is present in pernicious anaemia?
H+K+ - ATPase located in the gastric parietal cells of rodent stomach
64
What are the clinical presentations of pernicious anaemia?
The antibody is present in more than 90% of patients with pernicious anaemia
65
What condition can lead to pernicious anaemia? What is it characterised by?
**Autoimmune gastritis** this is characterised by antibodies to GPC and intrinsic factor
66

Y2 Clinical Pathology (76 decks)

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