RHEUMATOLOGY DIAGNOSTICS Flashcards
What are the 3 different types of investigations that can be done in rheumatology?
Blood tests
Joint (synovial) fluid analysis
Imaging (Xrays, ultrasound, CT, MRI)
What are the basic rheumatology blood tests that you should always order first before any fancy ones?
Full blood count (FBC) Urea and electrolytes (U&E) Liver function tests (LFT) Bone profile Erythrocyte sedimentation rate (ESR) C-reactive protein (CRP)
What tests make up a FBC?
Haemoglobin (Hb)
Mean cell volume (MCV)
White cell count (WCC)
Platelet count (PLT)
What does a FBC for a patient with inflammatory arthritis look like?
Hb: Low (anaemia) or normal
MCV: Normal (normocytic anaemia)
WCC: Usually normal
PLT: Normal or high (chronic inflammation)
What does a FBC for a patient with osteoarthritis look like?
Hb: Normal
MCV: Normal
WCC: Normal
PLT: Normal
What does a FBC for a patient with septic arthritis look like?
Hb: Usually normal (acute so hasn’t had time to drop)
MCV: Normal
WCC: High (usually neutrophils)
PLT: Usually normal or high (marked inflammation)
What tests make up a urea and electrolytes (U&E)?
Urea
Creatinine
Sodium
Potassium
What does a high creatinine indicate?
Worse renal clearance indicating problem with kidneys
Why is it important to do a U&E exam on a patient with rheumatological disease and give examples?
Rheumatological diseases can affect the kidneys:
- SLE (lupus nephritis)
- Vasculitis (glomerular nephritis)
- Chronic inflammation –> high serum amyloid A (SAA) –>
SAA deposits in organs (AA amyloidosis) –> renal
damage
NSAIDs can cause renal impairment
What tests make up the LFTs?
Bilirubin
Alanin aminotransferase (ALT)
Alkaline phosphatase (ALP)
Albumin
Why is it important to do LFTs on a patient with rheumatological disease?
DMARDs (e.g. methotrexate) can cause liver damage
What does a low albumin suggest?
Problem with synthesis in liver
or
Problem with kidneys causing leak
What is tested in a bone profile?
Calcium
Phosphate
Alkaline phosphatase (ALP)
What will be raised in patients with Paget’s disease of bone?
Alkaline phosphatase (ALP)
What is Paget’s disease of bone and what are its clinical features/how it presents?
Disease caused by abnormality of high bone turnover
Bone pain, excessive bone growth, fracture through area of abnormal bone
How will an osteomalacia patient’s bone profile look?
ALP: normal or high
Ca: normal or low
PO4: normal or low
How will an osteoporosis patient’s bone profile look?
ALP: normal
Ca: normal
PO4: normal
What are ESR and CRP markers for?
Inflammation
CRP more specific than ESR
What are some reasons other than inflammation that can cause ESR to be elevated?
Elevated immunoglobulin level
Paraprotein (myeloma)
Anaemia
Rises with age
In a patient with SLE, how will their ESR and CRP look?
ESR high, CRP normal
CRP can be high sometimes if there is significant synovitis or an inflammatory pleural/pericardial effusion
If CRP is low in SLE, have a low index of suspicion for infection
What are ANA and why is it useful?
Anti-nuclear antibodies
Directed at nuclear component of cell
High amount of ANA in combination with correct clinical features indicates an autoimmune connective tissue disorder (SLE, Sjorgren’s, scleroderma)
How are ANA levels reported?
Reported as a maximal dilution at which it is still detectable:
- 1:80 (weak), 1:1280 (strong)
If you suspect a patient has SLE and they test negative for ANA what does it mean?
Patient doesn’t have SLE
If ANA is positive what other tests should you order and what do positive results for each indicate?
Extractable nuclear antigens (ENA): a panel of 5
autoantibodies
- Ro (Lupus/Sjogren’s)
- La (Lupus/Sjogren’s)
- RNP (Lupus/mixed connective tissue disorder)
- Smith (Lupus)
- Jo-1 (Polymyositis)
dsDNA antibodies: Specific for SLE
Complement C3 and C4 levels (may be low in SLE)
What are the reasons for performing a joint aspiration?
To obtain synovial fluid for analysis
Therapeutic to relieve symptoms
For what conditions is joint analysis done?
Suspected septic arthritis
Diagnosing crystal arthritis
What are the differences between septic and reactive arthritis?
Synovial fluid culture:
- Septic arthritis +ve
- Reactive arthritis sterile
Antibiotic therapy:
- Septic arthritis - yes
- Reactive arthritis - no
Joint lavage:
- Septic arthritis - yes for large joints
- Reactive arthritis - no
What are the imaging techniques used in rheumatology and give reasons for using each
X-rays: first line, cheap, widely available
CT scans: more detailed bony imaging
MRI: best for soft tissue e.g. tendons/ligaments and spinal imaging
Ultrasound: like MRI but goof for smaller joints and worse for deep/large joints
What are the radiographic features of osteoarthritis?
Joint space narrowing
Subchondral bony sclerosis
Osteophytes
Subchondral cysts
What are the radiographic features of RA?
Soft tissue swelling
Peri-articular osteopenia
Bony erosions
Joint space narrowing
X-rays only show bony information which isn’t that helpful in early RA
What are the features seen via ultrasound for a patient with RA?
Synovial hypertrophy
Increased blood flow (doppler signal)
Erosions not seen on plain X-ray
Much better than X-ray at detecting synovitis
What imaging is done for RA?
X-ray
Ultrasound
MRI
What are the radiographic changes in RA compared to OA?
Joint space narrowing:
- RA yes, OA yes
Subchondral sclerosis:
- RA no, OA yes
Osteophytes:
- RA no, OA yes
Osteopenia:
- RA yes, OA no
Bony erosions:
- RA yes, OA no
What radiographic features can be seen in a patient with gout?
After time, rate-bite erosions at the MTPJ of the great toe
What radiographic features can be seen in a patient with psoriatic arthritis?
Asymmetrical joint involvement
Erosions of IPJs
MCPJs not affected (unlike RA)
What are Heberden’s/Bouchard’s nodes?
In OA:
- Heberden’s are osteophytes at distal IPJs
- Bouchard’s are osteophytes at proximal IPJs
