Rheumatology Diagnostics Flashcards
what are the major divisions of arthritis?
osteoarthritis
inflammatory arthritis
septic arthritis
what are the bloods for inflammatory arthritis?
Hb low (anaemia) or normal
MCV normal
WCC normal
PLT normal or increased
what are the bloods for oesteoarthrits?
Hb, MCV, MCC, PLT all normal
what are the blood for septic arthritis?
Hb usually normal
MCV normal
WCC increased (leucocytosis)
PLT normal or increased
what does U & E results measure?
urea
creatinine
sodium
potassium
what does creatinine show?
Higher Cr= worse renal clearance = kidney problems
what rheumatoid diseases can affect the kidneys?
- Systemic lupus erythematous (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)
- Non-steroidal anti-inflammatory drugs (NSAIDs) can cause kidney impairment
what do LFTs measure?
- Bilirubin
- Alanine aminotransferase (ALT)
- Alkaline phosphatase (ALP)
- Albumin
what needs to be done on patients on methotrexate?
regular blood tests (Every 8 weeks)
DMARDs (methotrexate) can cause liver damage
what can low albumin indicate?
problem of synthesis (in liver)
the problem of a leak from kidney (e.g lupus nephritis)
what does a bone profile indicate?
- Calcium
- Phosphate (PO4)
- Alkaline phosphatase (ALP)
why is ALP measured in bone and liver
ALP can be found in bone or liver
what is Page’s disease?
disease caused by abnormality of high bone turnover
what are the clinical features of paget’s disease?
bone pain
excessive pain growth
fracture through area of abnormal bone
what are the bone profile results for osteomalacia?
ALP normal or increased
CA and PO4 normal or low
what is osteomalacia?
soft bones due to vitamin D deficiency
what is osteoporosis?
low bone density
what is the bone profile for osteoporosis?
calcium, PO4 and ALP normal?
how is osteoporosis diagnosed?
DEXTA scan
what is ESR & CRP?
marker of inflammation
why might ESR be raised other than inflammation?
- Elevated immunoglobulin level
- Paraprotein (myeloma)
- Anaemia
- Tends to rise with age
is ESR or CRP more specific for inflammation?
CRP
which is more useful ESR or CRP 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 2 types of autoantibodies in RA?
rheumatoid factor
cyclin 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 !
- Positive in 70% at disease onset and further 10-15% become positive over the first 2 years of diagnosis
what does CCP antibodies show?
more specific than RF
worse prognosis associated
what are anti-nuclear antibodies?
- Antibodies directed at nuclear component of the cell –
when is ANA test ordered?
- only order if suspect autoimmune CT diseases clinically
what are the non specific causes of altered ANA?
- 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
what are the rheumatological uses of ANA?
- 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 the signs of SLE?
- Arthritis/ arthralgia
- Skin rash (photosensitive)
- Mouth ulcers
- Kidney disease
- Haematological abnormalities
- Pleural effusion
- Pericardial effusion
what are the signs of Sjogren’s syndrome?
- Dry eyes
- Dry mouth
- Extra-articular features
what are the signs of scleroderma
- Vasculopathy (esp Raynaud’s phenomenon)
- Skin thickening
- Organ fibrosis
what are the signs of polymyositis?
- Muscle inflammation
- Weakness
- High CK
how is ANA interpreted?
- Strength of ANA is reported as maximal dilution at which it is still detectable
- eg 1:80 (weak), 1:320, 1:640, 1:1280 (strong)
- Negative test rules out SLE
what does negative ANA rule out?
SLE
what does a positive test suggest?
- Positive test does 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 other tests should be done if ANA is positive?
ENA: panel of 5 autoantibodies
dsDNA (double stranded DNA antibodies)
complement C3 and C4
what are the ENA tests and what diseases do they suggest?
- Ro- Lupus or Sjogrens syndrome
- La- lupus or Sjogren’s syndrome
- RNP- lupus or mixed connective tissue disorder
- Smith- lups
- Jo-1- Polymyositis
what is dsDNA useful for?
- highly specific for lupus
- associated with renal involvement
- useful for tracking lupus activity over time
what is complement C4 and C3 useful for?
may be decreased in active lupus
how is synovial fluid obtained?
aspiration fluid from a joint
what are the indications for joint aspiration?
- diagnostic: to obtain synovial fluids for analysis
- therapeutic: to relieve symptoms (+/- concurrent steroid injections)
what are the diagnostic uses of synovial fluid analysis?
suspected septic arthritis
diagnosing crystal arthritis
how is synovial fluid used for septic arthritis?
- gold standard for diagnosis
- send for MC&S
- enables causative organism to be identified
- sensitivities from culture guide antibiotic choice
how is synovial fluid used for crystal arthritis?
- Gout and pseudogout
- Aspiration and examining under microscope using polarised light
- Gout: needle shaped with negative birefringence
- Pseudogout: rhomboid shaped with positive birefringence
what are the differences in septic arthritis and reactive arthritis?
- Synovial fluid
- SA= positive
- RA= sterile
- Antibiotic therapy
- SA= yes
- RA= no
- Joint lavage
- SA= yes- for large joints
- RA= no
what is the first line imaging in rheumatology?
X-rays: first-line, cheap, widely available
why are MRI useful in rheumatology?
- 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 ultrasound useful in rheumatology?
- Like MRI can visualize soft tissue structures.
- Good for smaller joints, less good for deep/large joints like knee or hip
what are the x-ray findings for osteoarthritis?
- Plain X-rays remain the most useful test in the diagnosis of OA
- Radiographic features of osteoarthritis:
- Joint space narrowing (bone touching bone)
- Subchondral bony sclerosis
- Osteophytes
- Subchondral cysts
what is the ray finding in Rheumatoid arthritis?
- Soft tissue swelling
- Peri-articular osteopenia
- Bony erosions- established disease occurance
what is the aim of treatment of RA?
treat early before erosions (permanent damage) occur
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
what are the differences in radiographic changes between RA and osteoarthritis?
what does joint space narrowing indicate?
- articular cartilage loss
- In RA is secondary damage due to synovitis
- In OA is primary abnormality
what are osteophytes in different locations called?
- Osteophytes at the distal interphalangeal joints= Heberden’s nodules,
- at proximal inter-phalangeal joints= Bouchard’s nodules
what is a common early radiographic sign of inflammatory arthritis in any cause?
juxta-articular osteopenia
where do bone erosions initially occur?
at the margins of the joint where the synovium is in direct contact with bone (the bare area)
