Rheumatology Diagnositics Flashcards
What are the different types of rheumatology diagnostics?
- Blood tests
- Join (synovial) fluid analysis
- Imaging tests, X ray, US, CT, MRI
What are the basic rheumatology blood tests?
- Full blood count (FBC)
- Urea and electrolytes (U&E)
- Liver function tests (LFT)
- Bone profile
- Erythrocyte sedimentation rate (ESR)
- C-reactive protein (CRP)
What is arthritis?
disease of joints
What are the major divisions of arthritis?
- Osteoarthritis (degenerative arthritis)
- Inflammatory arthritis (main type RA)
- Septic arthritis
What does the test for Hb show?
- Inflammatory arthritis: decreased (anaemia) or normal
- Osteoarthritis: normal
- Septic arthritis: usually normal
What does the test for MCV show?
- Inflammatory arthritis: normal
- Osteoarthritis: normal
- Septic arthritis: normal
What does the test for WCC show?
- Inflammatory arthritis: usually normal
- Osteoarthritis: normal
- Septic arthritis: increased (leucocytsosis)
What does the test for PLT show?
- Inflammatory arthritis: normal or increased
- Osteoarthritis: normal
- Septic arthritis: normal or increased
What urea and electrolytes do you measure?
Urea (U)
Creatinine (Cr)
Sodium
Potassium
What do high creatinine levels indicate?
worse renal clearance (indicating kidney problem)
How does SLE affect the kidneys?
lupus nephritis
How does vasculitis affect the kidneys?
neohritis
How does chronic inflammation affect kidneys?
high levels of serum amyloid A (SAA) protein -> SAA deposits in organs (AA amyloidosis)
How can NSAIDs affect the kidneys?
cause kidney impairment
What Liver function tests do you carry out?
- Bilirubin
- Alanine aminotransferase (ALT)
- Alkaline phosphatase (ALP)
- . Albumin
Why do you do LFTs in rheuamtology?
- Disease modifying anti-rheumatic drugs (DMARDs) (eg methotrexate) can cause liver damage.
- patients on methotrexate need regular blood tests (eg every 8 weeks).
What does low albumin indicate?
reflect problem of synthesis (in liver) or problem of leak from kidney (eg in lupus nephritis)
What do you measure in a bone profile?
- Calcium
- Phosphate (PO4)
- . Alkaline phosphatase (ALP) nb also in LFTs – confusingly the source of ALP can be bone OR liver
What is high in Paget’s disease?
ALP
What is Paget’s disease?
- disease caused by abnormality of high bone turnover
2. Clinical features: bone pain, excessive pain growth, fracture through area of abnormal bone
What is osteomalacia?
soft bones due to vitamin D deficiency
What are the levels like in osteomalacia?
- ALP normal or ↑
2. Ca and PO4 normal or ↓
What is osteoporosis?
low bone density
What are the levels like in osteoporosis?
usually calcium, PO4 and ALP normal
What are two useful markers of inflammation?
ESR and CRP
When can ESR be elected but not necessarily form inflammation?
- Elevated immunoglobulin level
- Paraprotein (myeloma)
- Anaemia
- Tends to rise with age
What is more specific for inflammation?
CRP
What are the rule of thumb with CRP and ESR in SLE?
- ESR usually high but CRP normal
- Exceptions to the rule: CRP high in SLE if there is significant synovitis or there is an inflammatory pleural or pericardial effusion
- If CRP in lupus, have a low index of suspicion for infection
What are the two types of antibodies found in the blood of RA patients?
- Rheumatoid factor
2. Cyclic Citrulinated peptides (CCP) antibodies
What is RF?
- Antibodies that recognize the Fc portion of IgG as their target antigen typically IgM antibodies i.e. IgM anti-IgG antibody !
- Positive in 70% at disease onset and further 10-15% become positive over the first 2 years of diagnosis
What are CCP antibodies?
- More specific than RF
2. Associated with worse prognosis
What are anti-nuclear antibodies? (ANA)
antibodies directed at nuclear component of the cell
How specific are ANA?
Non-specific
Are ANA common?
- Relatively common in general healthy population at low titre (level)
- Prevalence of ANA increases with age in the general population
- Sometimes transiently positive following infection
When is ANA used in rheumatology diagnosis?
High titre ANA in combination with the correct clinical features may indicate one of the autoimmune connective tissue diseases (eg SLE, Sjogren’s syndrome, scleroderma)
What are some autoimmune connective tissues diseases?
- SLE
- Scleroderma
- Sjogren’s syndrome
- Polymyositis
What are the features of SLE?
- Arthritis
- Skin rash
- Mouth ulcers
- Kidney disease
- Haematological
- Pleural effusion
- Pericardial effusion
What are the features of scleroderma?
- Vasculopathy (esp. Raynaud’s phenomenon)
- Skin thickening
- Organ fibrosis
What are the features of Sjogren’s syndrome?
- Dry eyes
- Dry mouth
- Extra-articular features
What are the features of polymyositis?
- Muscle inflammation
- Weakness
- High CK
What does a negative tests of Anti-nuclear antibodies (ANA) rule out?
SLE
What does a positive test of ANA mean?
- not necessarily mean SLE
- but suggestive IF there are other clinical and lab features to support the diagnosis
- a stronger test is more likely to be clinically significant
What is the strength of ANA like?
reported as maximal dilution at which it is still detectable
eg 1:80 (weak), 1:320, 1:640, 1:1280 (strong)
What other tests do you order if ANA is positive?
ENA (extractable nuclear antigens): a panel of 5 autoantibodies
What ENAs do you order and what do they indicate?
- Ro: Lupus or Sjogrens syndrome
- La: Lupus or Sjogrens syndrome
- RNP: Lupus or mixed connective tissue disease
- Smith: Lupus
- Jo-1: Polymyositis
In lupus what antibodies are highly speicifc?
Double stranded (dsDNA) antibodies
What is dsDNA used for?
- associated with renal involvement
- useful for tracking lupus activity over time
What are the complement
levels C3 and C4 like in lupus?
may be ↓ in active lupus
How is synovial fluid analysed?
Obtained by aspirating fluid from a joint
What are the indications for joint aspiration?
a) Diagnostic: to obtain synovial fluid for analysis
b) Therapeutic: to relief symptoms (+/- concurrent steroid injection)
What are the two main diagnostic uses for aspiration?
- Suspected septic arthritis
2. Diagnosing crystal arthritis
How does aspiration help in suspected septic arthritis?
- gold standard for diagnosis
- send for MC&S
- enables causative organism to be identified
- sensitivities from culture guide antibiotic choice
How can the diagnosis of crystal arthritis be made?
aspirating fluid from the affected joint and examining it under a microscope using polarized light
How does gout look?
needle shaped crystals with negative birefringence
How does pseudogout look?
rhomboid shaped crystals with positive birefringence
What is the synovial fluid culture like in septic arthritis and reactive arthritis?
- Septic arthritis: positive
- Reactive arthritis: sterile
What is the antibiotic therapy like in septic arthritis and reactive arthritis?
- Septic arthritis: yes
- Reactive arthritis: no
What is the joint lavage like in septic arthritis and reactive arthritis?
- Septic arthritis: yes (for large joints)
- Reactive arthritis: no
When are X rays done?
first line, cheap, widely available
What are CTs done?
more detailed bony imaging
When is MRI done?
- Best visualization of soft tissue structures like tendons and ligaments
- Best for spinal imaging: can see spinal cord and exiting nerve roots
- Expensive and time-consuming
When is USS done?
- Like MRI can visualize soft tissue structures.
2. Good for smaller joints, less good for deep/large joints like knee or hip
When are plain X rays the most useful test?
diagnosing OA
What are the radiographic features of OA?
- Joint space narrowing
- Subchondral bony sclerosis
- Osteophytes
- Subchondral cysts
What are the radiographic features of RA?
- Soft tissue swelling
- Peri-articular osteopenia
- Bony erosions
When are there bony erosions in RA?
- established disease
- aim of modern therapy is to treat EARLY before erosions (permanent damage) has occurred
- Informatiion from X-rays is limited to bony structures
When is US used in RA?
- detecting synovitis
- US (usually of hands and wrists) can be performed alongside clinical assessment in a dedicated early arthritis clinic
What are the us changes in RA?
- Synovial hypertrophy (thickening)
- Increased blood flow (seen as doppler signal)
- May detect erosions not seen on plain X-ray
Can MRI be used in RA?
yes but expensive and time-consuming
Is there joint space narrowing in RA and OA?
- RA: yes
- OA: yes
Is there subchondral sclerosis in RA and OA?
- RA: no
- OA: yes
Is there osteophytes in RA and OA?
- RA: no
- OA: yes
Is there osteopenia in RA and OA?
- RA: yes
- OA: no
Is there bony erosions in RA and OA?
- RA: yes
- OA: no
What are the radiographic features of gout?
juxta-articular ‘rat bite’ erosions at the MTPJ of the great toe
What are the radiographic features of psoriatic arthritis?
- Asymmetrical pattern of joint involvement
- Erosions of IPJs
- MCPJs not affected (unlike RA)