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brs (phase 1b) > (msk) rheumatology diagnostics > Flashcards

(msk) rheumatology diagnostics Flashcards

1
Q

what are diagnostics?

A

laboratory tests and imaging studies

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2
Q

what are the three categories of rheumatology diagnostics?

A

1) blood tests
2) joint (synovial) fluid analysis
3) imaging tests (mainly x-rays but also ultrasound, CT, MRI)

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3
Q

which imaging is used most commonly in rheumatology?

A

mainly x-rays but also ultrasound, CT, MRI

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4
Q

how do you go about ordering blood tests for a rheumatological patient?

A
  • ask yourself: do you even need any blood tests? = diagnosis may be clear from history and examination alone (e.g. osteoarthritis of the knee)
  • start with the basic blood tests before ordering ‘fancy’ tests
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5
Q

what are the basic, baseline rheumatology blood tests?

A 
FBC (full blood count)
U&E (urea & electrolytes)
LFT (liver function tests)
bone profile
ESR (erythrocyte sedimentation rate)
CRP (C-reactive protein)
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6
Q

define arthritis

A

pain and swelling (inflammation) in the joint

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7
Q

what are the three broad divisions of arthritis?

A

osteoarthritis (degenerative) = cartilage is worn out (non-inflammatory)

inflammatory = inflammation usually caused by autoimmune disease; most common is rheumatoid arthritis

septic = infection in joint, inflammation arises secondary to that

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8
Q

what would the full blood count result for a patient with inflammatory arthritis be?
(refer to Hb, MCV, WBCC, platelets)

A

Hb = normal or reduced (anaemia of chronic inflammation, ACD)

MCV = normal (ACD is usually normocytic)

WBC = normal

platelets = normal or elevated (ACD can cause reactive increase in platelets)

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9
Q

explain how chronic inflammation can lead to anaemia

A

long-standing, uncontrolled inflammation suppresses the bone marrow
= less production of RBCs (normocytic anaemia)

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10
Q

what type of anaemia is usually present in inflammatory arthritis?

A

normocytic anaemia

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11
Q

what would the full blood count result for a patient with osteoarthritis be?
(refer to Hb, MCV, WBCC, platelets)

A

Hb = normal

MCV = normal

WBC = normal

platelets = normal

(non-inflammatory so likely to have normal FBC)

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12
Q

what would the full blood count result for a patient with septic arthritis be?
(refer to Hb, MCV, WBCC, platelets)

A

Hb = normal

MCV = normal

WBC = normal or elevated (leukocytosis - due to elevated neutrophils as a result of bacterial infection)

platelets = normal or elevated

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13
Q

what is assessed as part of a U&E blood test?

A

urea
creatinine
sodium
potassium

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14
Q

why is plasma creatinine an important blood test?

A

higher creatinine

= worse renal clearance (indicating kidney problem secondary to rheumatic disease)

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15
Q

what is assessed as part of a U&E blood test?

A

urea
creatinine
sodium
potassium

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16
Q

give examples of the systemic manifestations of rheumatic disease that affect the kidney

A

1) systemic lupus erythematous (SLE) = lupus nephritis (kidney inflammation)
2) vasculitis = nephritis (e.g. glomerularnephritis)
3) amyloidosis = chronic inflammation in poorly controlled inflammatory disease -> high levels of serum amyloid A (SAA) protein -> SAA deposits in organs (AA amyloidosis)

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17
Q

when does amyloidosis occur?

A

when chronic inflammation is poorly controlled, as part of the acute phase response in the liver, serum amyloid A protein is produced (SAA)

serum levels of SAA elevated so deposition occurs in the organs forming amyloid plaques = amyloidosis

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18
Q

which drug is commonly associated with kidney damage?

A

non-steroidal anti-inflammatory drugs (NSAIDs) (e.g. ibuprofen) can cause kidney impairment

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19
Q

what is assessed as part of an LFT blood test?

A

bilirubin
alanine aminotransferase (ALT)
alkaline phosphatase (ALP)
albumin

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20
Q

why is it important to do LFTs in a rheumatic patient?

A

disease-modifying anti-rheumatic drugs (DMARDs) = treatment
= (e.g. methotrexate) can cause liver damage

SO patients on methotrexate have to have regular blood tests (e.g. every 8 weeks)

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21
Q

what is assessed as part of a LFT blood test?

A

bilirubin
alanine aminotransferase (ALT)
alkaline phosphatase (ALP)
albumin

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22
Q

what are the two possible interpretations of a low albumin level?

A

can either reflect a problem of synthesis (in liver)

or a problem of leakage from kidney due to reduced oncotic pressure (e.g. in lupus nephritis)

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23
Q

what is assessed as part of bone profile?

A

calcium
phosphate (PO4)
alkaline phosphatase (ALP)

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24
Q

why is ALP part of the liver function tests and bone profile as well?

A

the source of ALP can be bone OR liver

i.e. production in the bone OR liver

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25
Q

what is Paget’s disease of bone?

A

disrupts the normal cycle of bone renewal, causing bones to become weakened and possibly deformed

(disease caused by abnormality of high bone turnover)

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26
Q

what ALP levels are expected in Paget’s disease of bone?

A

very elevated ALP levels

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27
Q

what are the clinical features of Paget’s disease of bone?

A

bone pain, excessive pain growth, fracture through area of abnormal bone

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28
Q

why is ALP elevated in Paget’s?

A

ALP is formed by the bone-forming osteoblasts

in Paget’s, osteoclast malfunction results in a much faster rate of bone resorption so as a compensatory mechanism, osteoblast activity is significantly increased (new bone is larger and weaker than normal tho)

side effect of increased osteoblast activity is increased ALP production

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29
Q

what bone profile is expected in Paget’s disease?

refer to calcium, phosphate and ALP

A

very elevated ALP

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30
Q

what bone profile is expected in osteomalacia?

refer to calcium, phosphate and ALP

A

ALP normal or ↑, Ca and PO4 normal or ↓

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31
Q

what bone profile is expected in osteoporosis?

refer to calcium, phosphate and ALP

A

calcium, PO4 and ALP normal usually

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32
Q

how is osteoporosis diagnosed?

A

DEXA scan

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33
Q

what are the two markers of inflammation in a blood test?

A

CRP and ESR

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34
Q

which is the preferred marker of inflammation: CRP or ESR - and why?

A

usually, CRP is the more specific one of the two as ESR can be elevated for many other reasons (elevated immunoglobulin level, paraprotein (myeloma), anaemia, tends to rise with age)

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35
Q

what are possible reasons why ESR can be elevated, besides inflammation?

A

elevated immunoglobulin level
paraprotein (myeloma)
anaemia
tends to rise with age

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36
Q

what are CRP and ESR levels like in SLE?

A

ESR is usually high but CRP normal

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37
Q

when is CRP elevated in SLE?

A

if there is significant synovitis or there is an inflammatory pleural or pericardial effusion

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38
Q

when is CRP elevated in SLE?

A

if there is significant synovitis or there is an inflammatory pleural or pericardial effusion

BUT if CRP in lupus, have a low index of suspicion for infection = always suspect new infection first thing!

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39
Q

which two autoantibodies are found in the blood of patients with rheumatoid arthritis?

A

rheumatoid factor (RF)

cyclic citrullinated peptides (CCP) antibodies

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40
Q

when would you think about carrying our specific, specialist rheumatological tests?

A

prolonged morning stiffness, over-stiffness on joint examination

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41
Q

what is rheumatoid factor?

A

antibodies that recognize the Fc portion of IgG as their target antigen + are typically IgM (pentameric) antibodies themselves
i.e. IgM anti-IgG antibody

42
Q

how common is rheumatoid factor in RA patients?

A

positive in 70% at disease onset and further 10-15% become positive over the first 2 years of diagnosis

43
Q

which antibody is more specific to rheumatoid arthritis: RF or anti-CCP?

A

testing for the CCP is more specific to RA patients + the presence of CCP antibodies is associated with a worse prognosis (more aggressive disease)

44
Q

if anti-CCP is present, what can be concluded about the type of RA?

A

presence of anti-CCP antibodies is associated with a worse prognosis (more aggressive disease)

45
Q

what are anti-nuclear antibodies?

A

antibodies directed at the nuclear component of the cell

46
Q

explain how anti-nuclear antibodies are non-specific

A
  • relatively common in the normal, healthy population at low titre (level)
  • prevalence of ANA increases with age in the general population
  • sometimes transiently positive following infection
47
Q

when are ANAs useful in rheumatology?

A

high titre ANA together with the correct clinical features may indicate one of the autoimmune connective tissue diseases (eg SLE, Sjogren’s syndrome, scleroderma)

48
Q

why must you cautiously order ANA blood tests in rheumatology?

A

as they are non-specific, will show up positive in most healthy individuals as well - so must order judiciously!

= to prevent it leading to anxiety and unnecessary referral to hospital and further investigation

(!!) SO = only order if you suspect autoimmune connective tissue disease clinically (!!)

49
Q

name four autoimmune connective tissue diseases

A

systemic lupus erythematosus
scleroderma
Sjogren’s syndrome
polymyositis

50
Q

what are the clinical features of systemic lupus erythematosus?

A

arthritis
skin rash
mouth ulcers

kidney disease
haematological

pleural effusion
pericardial effusion

51
Q

what are the clinical features of Sjogren’s syndrone?

A

dry eyes
dry mouth
extra-articular features

52
Q

what are the clinical features of Sjogren’s syndrome?

A

dry eyes
dry mouth
extra-articular features

53
Q

what are the clinical features of scleroderma?

A

vasculopathy (esp. Raynaud’s phenomenon)
skin thickening
organ fibrosis

54
Q

how is an ANA result reported?

A

either negative for ANA (no ANA) or positive with a dilution ratio

55
Q

what is the ANA dilution ratio?

A

the way to report the strength of ANA

= maximal dilution at which it is still detectable

e.g. 1:80 (weak), 1:320, 1:640, 1:1280 (strong)

56
Q

which ANA dilution is stronger: 1:80 or 1:1280?

A

1:1280

as after 1280 dilutions, ANA are still at detectable levels whereas with 1:80, ANA is only detectable up until 80 dilutions

57
Q

what does a negative ANA mean?

A

exclude the diagnosis of SLE

58
Q

what does a negative ANA mean in terms of SLE?

A

can exclude the diagnosis of SLE

59
Q

what does a positive ANA mean in terms of SLE?

A

does not necessarily mean SLE but can be suggestive of SLE if there are clinical and lab features to support the diagnosis of SLE

stronger test = more clinically significant

60
Q

which tests are ordered if an ANA comes back positive for SLE?

A

1) ENA (extractable nuclear antigens) = a panel of 5 autoantibodies tested for
2) dsDNA
3) complement levels C3 and C4

61
Q

what is tested in an ENA?

A

the presence of Ro, La, RNP, Smith and Jo-1 antibodies

62
Q

why is an ENA test carried out after an ANA comes back positive?

A

positive ANA + clinical features = suggests SLE

so need to narrow down and find out which antibody is causing the specific positive result

63
Q

what are Ro antibodies a sign of?

A

lupus or Sjogren’s syndrome

64
Q

what are La antibodies a sign of?

A

lupus or Sjogren’s syndrome

65
Q

what are RNP antibodies a sign of?

A

lupus or mixed connective tissue disease

66
Q

what are Smith antibodies a sign of?

A

lupus

67
Q

what are Jo-1 antibodies a sign of?

A

polymyositis

68
Q

why are dsDNA antibodies tested for in patients with suspected lupus?

A

highly specific for lupus, associated with renal involvement, useful for tracking lupus activity over time

69
Q

why are complement C3 and C4 tested for in patients with suspected lupus?

A

may be decreased in active lupus

70
Q

summarise the blood tests carried out for a patient with suspected SLE

A

basic = FBC, U&E, ESR, CRP, LFT, bone profile

specific antibodies = RF, CCP antibodies, ANA

super-specific = ENA, dsDNA, C3 & C4

71
Q

how is synovial fluid obtained for analysis?

A

obtained by aspirating fluid from a joint

72
Q

what are the indications for joint aspiration?

A

diagnostic: to obtain synovial fluid for analysis
therapeutic: to relieve symptoms (+/- concurrent steroid injection)

73
Q

what are the two main diagnostic uses for aspiration?

A

suspected septic arthritis

diagnosing crystal arthritis (e.g. gout, pseudogout)

74
Q

how is suspected septic arthritis diagnosed?

A

gold stand for diagnosis is synovial fluid aspiration and analysis

send for microbial culture and sensitivities

= causative organism can be identified and sensitivities can guide the antibiotic choice

75
Q

what does crystal arthritis include?

A

gout, pseudogout

76
Q

how is the diagnosis of crystal arthritis made?

A

by aspirating fluid from the affected joint and examining it under a microscope using polarized light

77
Q

how do gout crystals appear under polarised light?

A

needle-shaped crystals with negative birefringence

78
Q

how do pseudogout crystals appear under polarised light?

A

rhomboid-shaped crystals with positive birefringence

Pseudogout = Positive

79
Q

what are the key differences between septic arthritis and reactive arthritis?

A

synovial fluid culture

  • septic = positive
  • reactive = sterile

antibiotic therapy

  • septic = yes
  • reactive = no

joint lavage

  • septic = yes (larger joints)
  • reactive = no
80
Q

what imaging modalities are used in rheumatology?

A

x-rays
CT scans
MRI
ultrasound

81
Q

which imaging modality is preferentially used in rheumatology and why?

A

x-rays

= first-line, cheap, widely available

82
Q

when would CT scans be used in rheumatology?

A

more detailed bony imaging

83
Q

when would MRI scans be used in rheumatology?

A

best visualization of

1) soft tissue structures like tendons, ligaments
2) spinal imaging (can see spinal cord, exiting nerve roots and discs)

BUT
= expensive and time-consuming (so no usually used)

84
Q

when would ultrasound scans be used in rheumatology?

A

best visualization of soft tissue structures

  • good for smaller joints, less good for larger hip/knee joints
85
Q

what imaging modality is used to investigate osteoarthritis?

A

plain X-rays remain the most useful test in the diagnosis of osteoarthritis

86
Q

what are the radiographic features of osteoarthritis?

A

joint space narrowing (bone on bone)

osteophytes (extra bone growth; bone spurs)

subchondral bony sclerosis (increased white space)

subchondral cysts (cysts under cartilage)

87
Q

what imaging modality is used to investigate rheumatoid arthritis?

A

1) x-rays
2) ultrasound
3) MRI

88
Q

what are the radiographic features of rheumatoid arthritis on an X-ray?

A

soft tissue swelling
peri-articular osteopenia
bony erosions (sign of established disease - but want to treat EARLY before this stage is reached)

(but info is limited to bony structures)

89
Q

why is ultrasound sometimes better than an X-ray at detecting rheumatoid arthritis?

A

much better test for detecting synovitis

90
Q

what are the radiographic features of rheumatoid arthritis on an ultrasound?

A

synovial hypertrophy (thickening)

increased blood flow (seen as doppler signal)

may detect erosions not seen on plain X-ray

91
Q

what happens in an early arthritis clinic?

A

ultrasound (usually of hands and wrists) can be performed alongside clinical assessment in a dedicated early arthritis clinic

= for earlier diagnosis and treatment

92
Q

why is an MRI scan not usually used for rheumatoid arthritis?

A

time-consuming and expensive

93
Q

compare the radiographic changes seen in rheumatoid arthritis and osteoarthritis

A

RA:

  • joint space narrowing
  • peri-articular osteopenia
  • bony erosions

OA:

  • joint space narrowing
  • osteophytes
  • subchondral sclerosis
94
Q

what does joint space narrowing indicate?

A

indicates articular cartilage loss

= occurs in OA (primary abnormality) and RA (secondary to synovitis)

95
Q

what are osteophytes at the distal interphalangeal joints called?

A

Heberden’s nodes

96
Q

what are osteophytes at the proximal interphalangeal joints called?

A

Bouchard’s nodes

97
Q

what is juxta-articular osteopenia a common sign of?

A

inflammatory arthritis

98
Q

where do bony erosions occur in arthritis?

A

erosions occur initially at the margins of the joint where the synovium is in direct contact with bone

(seen over time)

99
Q

what do subchondral scleroses look like on a plain radigraph?

A

dense area of bone just under the cartilage in your joints, and it looks like abnormally white bone along the joint line

100
Q

how does gout commonly present on a X-ray?

A

juxta-articular erosions

commonly at the MTPJ of the great toe

101
Q

what is the term use to describe gout of the MTPJ of the big toe?

A

podagra

most commonly affected

102
Q

how does psoriatic arthritis present on an X-ray?

A

asymmetry of joints involved

bony erosions of IPJs, MCPJs not affected

‘pencil and cup deformity’

brs (phase 1b) (71 decks)

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