investigations Flashcards
why would you do
- Hb
- Platelets
- neutrophils
- lymphocytes
Hb - for anaemia of chronic disease, most common in RA, Fe deficiency may be due to NSAIDs
Platelets - rise with inflammation or bleeding, fall in SLE
neutrophils - rise with inflammation, sepsis, prednisolone usage. Fall in SLE or with DMARD toxicity
Lymphocytes - fall in she or DMARD induced
why would you do
- U&E
- uric acid
- LFTs
- CK, ALT, LDH
U&E - rise due to NSAIDs, renal disease in lupus/vasculitis or gout
Uric acid - elevated in gout, but falls with inflammation
LFTs - hepatitic rise due to DMARD toxicity
CK, ALT, LDH - rise in myositis
when would you request an auto antibody screen?
if there is a high clinical suspicion of a particular disease
what auto antibody is tested for in RA suspicions?
Rheumatoid factor in RA. Anti-CCP and ACPA are more specific for RA than RF. Neither of these antibodies rise in a disease flare.
what antibodies can be used to test for SLE?
- Antinuclear antibodies ANAs
e. g Anti - dsDNA, anti RO and anti LA
what is Human leukocyte antigen B27 used to test for ? (HLA-B27)
strongly associated with ankylosing spondylitis, iritis and juvenile arthritis
found in 10% of white people
what is the use of a urinalysis?
renal disease can be first detected by blood/protein on the urine dip. This test is mandated in SLE and vasculitis.
what is the use of a synovial fluid analysis?
the most important investigation in suspected cases of septic arthritis and crystal arthropathy
send for gram stain and culture before antibiotic treatment if possible
polarised light microscopy may reveal negatively birefringent needle shaped crystals in gout or positively birefringent rhomboid shaped crystals in psuedo gout
what is the use of biopsy?
- temporal artery biopsy is commonly requested. However, vasculitis is patchy is giant cell arteritis so mat give false negatives
- muscle biopsy for polymyositis or dermatomyositis
- skin biopsy is useful in vasculitis, dermatomyositis and SLE
- lip/salivary gland for Sjogen’s
- lymph node in SLE to rule of lymphoma or TB
- synovial biopsies for rare tumours/TB
what is the use of nerve conduction studies and Electromyography?
NCS helps confirm peripheral nerve entrapment e.g in carpal tunnel
EMG records spontaneous and voluntary muscle activity and has characteristic abnormalities
what is the use of x ray?
good for assessing bone
reflects damage rather than ongoing disease activity
what is the use of ultrasoud?
for diagnosis of early synovitis and erosions in early RA and PsA.
Good for soft tissue structures like bursae and tendons.
May be used to guide joint injections and soft tissue injections such as for tenosynovitis
what is the use of MRI?
identification of early inflammation especially in spondyloarthritis.
good for knee and shoulder – to look for meniscal and ligament tears and rotator cuff tears.
Also used for investigation of myositis.
Contraindications are:
claustrophobia/pacemaker/metal body in eye/surgical clips in brain
what is dual energy x ray absorptiometry?
radiation dose about 1/10 of CXR dose
evaluation for osteoporosis. Estimated bone mineral density at different sites.
