rheum diagnostics Flashcards
what are the different types of rheumatology diagnostics
- blood tests
- joint(synovial) fluid analysis
- imaging tests: xrays, ultrasound,ct,mri
basic blood tests in rheumatology
fbc urea and electrolytes liver function tests bone profile erythrocyte sedimentation rate c reactive protein
what are the 3 main types of arthritis
osteorthritis
inflammatory
septic
what would you expect to see in fbc of inflammatory arthritis
low (in anaemia) or normal hb
normal mcv
usually normal wcc
normal/high platelets
what would you expect to see in fbc of osteoarthritis
normal hb
normal mcv
normal wcc
normal platelets
what would you expect to see in fbc of septic arthritis
usually normal hb
normal mcv
high wcc - leukocytosis
normal/high platelets
why might anaemia and therefore low hb occur in inflammatory arthritis
long standing uncontrolled inflammation can suppress bone marrow leading to less production of red cells
what are u&es ?
urea
creatinine
sodium
potassium
what does a higher creatinine suggest and why is it relevant to rheum
higher cr = worse renal clearance indicating kidney problem
rheum disease can affect kidneys
what can sle do to kidneys
can cause lupus nephritis - which is kidney inflammation
what can vasculitis do to kidneys
glomerular nephritis
what can chronic inflammation in poorly controlled inflammatory disease cause
high levels of serum amyloid (saa) protein leads to saa deposits in organs (aa amyloidosis)
what effects do NSAIDs e.g ibuprofen do to kidneys
can cause kidney impairment
what are the lfts
bilirubin
alanine aminotransferase
alkaline phosphatase
albumin
why are lfts a relevant test in rheumatology
dmards e.g methotrexate can cause liver damage
*patients on methotrexate need regular blood tests (e.g every 8wks)
what is low albumin a sign of?
can either reflect problem of synthesis (in liver) or problem of leak from kidney e.g in lupus nephritis
what is pagets disease
disease caused by abnormality of high bone turnover
what are the clinical features of pagets disease
bone pain, excessive pain growth
fracture through area of abnormal bone
when would you expect the alp to be very high
pagets disease of bone
what might you see in bone profile of osteomalacia (soft bone due to vit d def)
normal/high alp
normal/low ca and po4
what is osteoporosis
low bone density
bone profile seen in osteoporosis
usually ca, po4 and alp are normal
what are some other reasons esr may be high.
elevated immunoglobulin level
paraprotein (myeloma)
anaemia
tends to rise with age
what is the rule of thumb in sle
in regards to esr and crp
esr usually high but crp normal
exception: crp high in sle if significant synovitis/inflammatory pleural or pericardial effusion
if crp high in lupus - suspect infection
what if esr/crp are elevated and there is evidence of inflammatory arthritis what bloods should be done
look for 2 types of antibodies in blood:
- rheumatoid factor: antiIgG antibody
- cyclic citrullinated peptide antibodies
why is ccp helpful
more specific thanrf
associated with worse prognosis
what are anti nuclear antibodies
antibodies directed at nuclear component of cell
what is ana use in rheumatology
high titre ana in combination with correct clinical features may indicate autoimmune connective tissue diseases e.g sle, sjogrens, scleroderma
how can we interpret anas
negative test rules out sle
postive test - doesnt necessarily mean sle, other clinical features needed to support diagnosis
what to do if ana comes back positive
ena test of 5 autoantibodies: ro,la,rnp,smith,jo1
which of the 5 autoantibodies would be positive in lupus
ro,la,rnp,smith
which of the 5 autoantibodies would be positive in sjogrens syndrome
ro,la
what does positive jo1 on test mean
polymyositis
why is double stranded dna antibodies a useful test
highly specific for lupus, associated with renal involvement, useful for tracking lupus activity over time
when are c3 and c4 complement levels useful
may be low in active lupus
what are the 2 indications for joint aspiration
diagnostic - to obtain synovial fluid for analysis
therapeutic - to relieve symptoms
how is synovial fluid obtained
by aspirating fluid from joint
what are the 2 main diagnostic uses for aspiration
- suspected septic arthritis
- gold standard for diagnosis
- send for mc and s
- enables causative organism to be identified
- sensitivities from culture guide antibiotic choice - diagnosing crystal arthritis
key differences in septic and reactive arthritis
sa - positive synovial fluid culture whilst sterile in reactive
antibiotic therapy needed in septic arthritis
joint lavage needed in septic arthritis
imaging test in rheum
x rays - first line, cheap, widely available
ct scans - more detailed bony imaging
mri - best visualisation of soft tissue, best for spinal imaging, expensive and time consuming
us - like mri good for soft tissue, good for smaller joints, less good for large/deep joints
what is the most useful diagnostic test in oa
xrays
what are radiographic features seen in osteoarthritis
joint space narrowing
subchondral bony sclerosis
osteophytes
subchondral cysts
what are some radiographic features found on xrays of ra
soft tissue swelling
peri articular osteopenia
boney erosions - aim is to treat before erosions
us is much better at detecting synovitis. us changes in ra:
synovial hypertrophy
increased blood flow - doppler signal
may detect erosions
radiographic features of gout
juxta articular ‘rat bite’ erosions - at mtpjs
