Rheumatoid Diagnostics Flashcards
rheumatology diagnostics can be divided into?
blood tests
joint (synovial) fluid analysis
imaging: x-rays, ultrasound, CT, MRI
list ‘basic’ rheumatology blood tests
full blood count urea and electrolytes liver function tests bone profile erythrocyte sedimentation rate c-reactive protein
typical FBC in inflammatory arthritis
Hb: decreased/normal
MCV: normal
WCC: usually normal
platelets: normal or ^
typical FBC in osteoarthritis
Hb: normal
MCV: normal
WCC: normal
platelets: normal
typical FBC in septic arthritis
Hb: normal
MCV: normal
WCC: increased
platelets: normal/increased
FBC includes?
Hb
MCV
WCC
platelet count
U&E includes?
urea
creatinine
sodium
potassium
higher creatinine indicates?
worse renal clearance > kidney issues
give examples of how rheumatological diseases can affect the kidneys
SLE > lupus nephritis
vasculitis > nephritis
Chronic inflammation in poorly controlled inflammatory disease
-> high levels of serum amyloid A (SAA) protein -> SAA deposits in organs (AA amyloidosis)
what drug class can cause kidney impairment?
NSAIDs
liver function tests include?
bilirubin
alanine aminotransferase
alkaline phosphatase
relevance of LFTs in rheumatological diseases
DMARDs can cause liver damage
low albumin can indicate?
reflect problem of synthesis (in liver) or problem of leak from kidney (eg in lupus nephritis)
bone profile includes?
calcium
phosphate
alkaline phosphatase
bone profile of Paget’s disease
increased ALP
bone profile in osteomalacia
ALP normal or ^, Ca and PO4 normal or decreased
bone profile in osteoporosis
usually calcium, PO4 and ALP normal
ESR and CRP are useful markers for?
inflammation
increased ESR can be due to?
elevated immunoglobulin level
paraprotein (myeloma)
anaemia
tends to rise with age
typical ESR and CRP for SLE
ESR high
CRP normal
when is CRP high in SLE?
if there is significant synovitis or there is an inflammatory pleural or pericardial effusion
what two types of autoantibodies are found in the blood of rheumatoid arthritis?
rheumatoid factor
cyclic citrullinated peptides (CCP) antibodies
what is rheumatoid factor?
Antibodies that recognize the Fc portion of IgG as their target antigen typically IgM antibodies i.e. IgM anti-IgG antibody
is CCP more or less specific than rheumatoid factor?
more specific
cyclic citrullinated peptides (CCP) antibodies are associated with?
worse prognosis
anti-nuclear antibodies in general population
prevalence increases w/ age
sometimes transiently +ve following infection
relatively common at low level in gen pop
use of ANA in rheumatology
High titre ANA in combination with the correct clinical features may indicate one of the autoimmune connective tissue diseases
list autoimmune connective tissue diseases
SLE
scleroderma
polymyositis
Sjogren’s syndrome
clinical features of SLE
Arthritis Skin rash Mouth ulcers Kidney disease Haematological Pleural effusion Pericardial effusion
clinical features of scleroderma
Vasculopathy (esp. Raynaud’s phenomenon)
Skin thickening
Organ fibrosis
clinical features of polymyositis
Muscle inflammation
Weakness
High CK
clinical features of Sjogren’s syndrome
Dry eyes
Dry mouth
Extra-articular features
ANA interpretation
Strength of ANA is reported as maximal dilution at which it is still detectable
-ve rules out SLE
+ve doesn’t necessarily mean SLE, suggestive IF there are clinical + lab features to support the diagnosis
If ANA is +ve, other tests to order?
ENA (extractable nuclear antigens): a panel of 5 autoantibodies Double stranded (dsDNA) antibodies
ENA includes?
Ro > Lupus, Sjogrens La > Lupus, Sjogrens RNP > Lupus or mixed connective tissue disease Smith > Lupus Jo-1 > Polymyositis
Double stranded (dsDNA) antibodies test
highly specific for lupus, associated with renal involvement, useful for tracking lupus activity over time
Complement levels C3 and C4: may be ↓ in active lupus
how is synovial fluid obtained for analysis?
aspirating fluid from a joint
indications for joint aspiration
Diagnostic: to obtain synovial fluid for analysis
Therapeutic: to relief symptoms (+/- concurrent steroid injection)
two main diagnostic uses for aspiration?
suspected septic arthritis
diagnosing crystal arthritis
diagnosis of crystal arthritis is made by?
aspirating fluid from the affected joint and examining it under a microscope using polarized light
gout vs pseudogout crystal arthritis
gout: needle shaped crystals with negative birefringence
pseudogout: rhomboid shaped crystals with positive birefringence
septic arthritis vs reactive arthritis key differences
synovial fluid culture: SA +ve, RA sterile
antibiotic therapy: SA yes, RA no
joint lavage: SA yes, RA no
imaging for rheumatology
x-rays
CT
MRI
ultrasound
radiographic (x-ray) features in osteoarthritis
Joint space narrowing
Subchondral bony sclerosis
Osteophytes
Subchondral cysts
radiographic (x-ray) features in rheumatoid arthritis
Soft tissue swelling
Peri-articular osteopenia
Bony erosions
ultrasound features in rheumatoid arthritis
Synovial hypertrophy (thickening) Increased blood flow (seen as doppler signal) May detect erosions not seen on plain X-ray
radiographic (x-ray) features in psoriatic arthritis
asymmetrical pattern
erosions of interphalangeal joints
MCPJs not affected
