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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
Q

What does a positive ANA test suggest?

A

That an autoimmune disease is present

This does not make a specific diagnosis, it just suggests that some form of autoimmune disease is present

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26
Q

What is meant by the detection of DSDNA and ENAs?

A

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

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27
Q

What technique is used in detection of ENAs?

A

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
Q

What does ELISA stand for?

What is this test used for?

A

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
Q

What other method can be used for antinuclear autoantibody assessment?

A

Microbead-based immunoassay

30
Q

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

A
31
Q

I dsDNA, Sm

ii. La
iii. Ro
iv. Scl-70
v. Centromere

A
32
Q

What auto-antibodies are present in the following conditions?

i. Polymyositis
ii. Dermatomyositis
iii. Rheumatoid arthritis

A

I. Jo-I

ii. Mi-2
iii. CCP

33
Q

Which autoantibodies are seen in the following conditions?

i. Diffuse glomerulonephritis
ii. Membranous glomerulonephritis
iii. Neonatal heart block

A

I dsDNA - SLE with kidney disease

ii. Sm, Ro - SLE with kidney disease
iii. Ro - maternal antibody

34
Q

Which autoantibodies are present in the following conditions?

i. Raynaud’s phenomenon
ii. Fibrosis alveolitis
iii. Erosive joint damage

A

I. U1-RNP as part of overlap syndromes

ii. Jo-1 (in polymyositis), U1-RNP
iii. CCP - in RA and overlap syndromes

35
Q

What is alopecia?

A

“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
Q

What would the complement blood results look like in someone with SLE?

What about ANA by indirect immunofluorescence?

A

C4 and C3 will be low

ANA shows a positive, homogenous pattern

37
Q

What is the tool used for diagnosing SLE?

A

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
Q

What is rheumatoid factor?

A

An antibody (IgM, IgG or IgA) directed against the FC portion of IgG

39
Q

What types of diseases is rheumatoid factor associated with?

A

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
Q

When is Anti-CCP antibody (ACPA) used as a diagnostic tool?

How sensitive is it?

A

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
Q

What would a joint X ray look like in rheumatoid arthritis?

A

Peri-articular swelling with effusion of MCP joints

osteopenia

joint space narrowing and erosions

42
Q

What types of blood test results would be seen in rheumatoid arthritis?

Why is early treatment important?

A

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
Q

When are anti-neutrophilic cytoplasmic antibodies (ANCA) ordered?

A

They are ordered when vasculitis is queried

e.g. renal or ENT

44
Q

What are the symptoms of granulomatosis with polyangitis ?

A

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
Q

What are the symptoms of granulomatosis with polyangitis caused by?

What test is positive in this condition?

A

Granulomas and patchy necrosis in blood vessels

there would be a positive anti-neutrophil cytoplasm test

46
Q

What is the difference between cytoplasmic (c) ANCA and perinuclear (p) ANCA?

A

Cytoplasmic ANCA:

  • Granular fluorescence of neutrophil cytoplasm with nuclear sparing

Perinuclear ANCA:

  • ​apparent fluorescence of the nucleus only
47
Q

What is the difference between ANCA and anti-PR3/MPO?

A

ANCA is the pattern

anti-PR3/MPO is the autoantibody causing the condition

48
Q

What are the target antigens for cytoplasmic and perinuclear ANCA?

A

Cytoplasmic ANCA:

  • PR3 - 90%
  • MPO

Perinuclear ANCA:

  • MPO - 70%
  • PR3
49
Q

What are the symptoms and features of granulomatosis with polyangitis?

(Wegener’s cANCA anti-PR3 positive)

A

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
Q

What are the signs and symptoms of microscopic polyangitis?

pANCA anti MPO positive

A

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
Q

What are the signs and symptoms of Churg-Strauss syndrome?

A

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
Q

Complete the table for the clinical utility of ANCA testing?

A
53
Q

What is the clinical utility of a positive ANCA test?

A
  • Useful in suggesting the diagnosis in the proper clinical setting
  • histopathology remains the gold standard for diagnosis in most cases
54
Q

What do negative ANCA assays not exclude?

A

Negative ANCA assays do not exclude AASV

10-50% of patients may be ANCA negative

55
Q

What does persistence of ANCA in the absence of clinical indications suggest?

A

Persistence of ANCA in the absence of clinical indications of active disease DOES NOT indicate a need for continued treatment

56
Q

What does reemergence of ANCA positive in a patient who was ANCA negative whilst in remission suggest?

A

A risk of disease flare

the time to the flare is uncertain

57
Q

How is autoimmune liver disease screened for?

Why may it be screened for?

A

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
Q

What is looked for in the autoimmune liver disease screen for primary biliary sclerosis and autoimmune hepatitis?

A

Primary biliary sclerosis:

  • anti-mitochondrial antibody that is specific for PBS

Autoimmune hepatitis:

  • anti-smooth muscle and anti-liver/kidney/microsomal (LKS) antibodies
59
Q

What are the different types of autoantibodies in type 1 diabetes mellitus?

A
  1. Islet cell antibodies
  2. Anti-GAD65 and anti-GAD67
  3. Anti-insulinoma antigen 2 (IA-2)
  4. Insulin autoantibodies (IAA)
60
Q

What happens to the autoantibodies in type 1 DM with time?

A

They disappear with progression of disease and total destruction of B-islet cells

61
Q

Why do we test for the autoantibodies in type 1 DM?

A

To confirm presence of the disease

to identify relatives and patients at risk of developing autoimmune diabetes

62
Q

What happens in Addison’s disease?

Which autoantibodies can be detected?

A

There are clinical features as it impairs production of cortisol

you can detect autoantibodies targeting the adrenal cortex

63
Q

What antigen is present in pernicious anaemia?

A

H+K+ - ATPase located in the gastric parietal cells of rodent stomach

64
Q

What are the clinical presentations of pernicious anaemia?

A

The antibody is present in more than 90% of patients with pernicious anaemia

65
Q

What condition can lead to pernicious anaemia?

What is it characterised by?

A

Autoimmune gastritis

this is characterised by antibodies to GPC and intrinsic factor

66
Q
A

Y2 Clinical Pathology (76 decks)

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