Rheumatology Investigations Flashcards
what is included in a full blood count
haemoglobin, MCV, neutrophil count, lymphocyte count, eosinophil count, platelet count
what is the relevance of haemoglobin
may be low in most inflammatory conditions
may be an indicator of disease activity
may get iron deficiency anaemia with NSAIDs
what is the relevance of MCV
may be high in patients on sulfasalazine, methotrexate or azathiprine
low in iron deficiency
when is MCV of no significance
of Hb stable and B12 folate and TFTs normal
what is the relevance of neutrophil count
may be low in CTD (especially SLE and sjogrens)
neutropenia can be adverse effect of most DMARDs
occasionally raised in inflammatory arthritis
what is the relevance of lymphocyte count
may be low in CTD (especially SLE and sjogrens)
reduced by immunosuppressants
indicator of disease activity
what is the relevance of eosinophil count
raised in eosinophilic granulomatous with polyangiitis (churg-strauss)
indicator of disease activity
what is the relevance of plasma viscosity
high in inflammatory conditions
indicator of disease activity
why is there a risk of toxicity in renal impairment with methotrexate
as it is excreted renally
what rheumatological disease can cause renal impairment
CTD
what is the relevance of LFTs
DMARDS, allopurinol and NSAIDs can cause hepatitis
what is the relevance of corrected calcium
hyperparathyroidism may cause pseudogout/ calcium pyrophosphate arthropathy (CPPD)
what is the relevance of ferritin
low in iron deficiency
high in anaemia of chronic disease
in presence of iron deficiency can be artificially high in inflammatory disease as also acts as an acute phase reactant
what is the relevance of creatine kinase
raised in myositis
indicator of disease activity
may also be raised in muscle trauma and strenuous exercise
what is the relevance of uric acid
raised in gout
normal in about 30% of cases of acute gout
may get asymptomatic hyperuricaemia
what is the relevance of urine protein/ creatine ratio
may get glomerulonephritis as part of connective tissue disease or vasculitis
when do you do a synovial fluid microscopy and culture
suspected septic arthritis or crystal arthritis
what is very unlikely if RF negative
extra-articular manifestations of RA
who has a worse prognosis: sero negative or positive for RF in RA
sero negative
how sensitive and specific is RF for RA
70% sensitive
85% specific
how sensitive and specific is anti- CCP for RA
70% sensitive
98% specific
who has a worse prognosis: sero negative or positive for anti-ccp in RA
negative
how sensitive and specific is anti- nuclear antibody for SLE
98% sensitive non specific (13% of adults +ve titre of 1:80- positive in a wide range of diseases inc. RA)
what is anti-dsDNA specific for and how specific
95% specific for SLE
can anti-dsDNA be used to monitor disease activity
yes
what does ENA stand for
extractable nuclear antigens
what can anti-RNP be positive in
usually in mixed connective tissue disease
can be in SLE
what can anti-centromere be positive in
limited systemic sclerosis
what can anti-Scl 70 be positive in
diffuse systemic sclerosis
what can anti-Ro and anti:La be positive in
primary sjogrens syndrome
what can anti-Jo-1 be positive in
inflammatory myositis
what can anti-Sm be positive in
very specific for lupus but in UK only in 3% of cases
what can anti-cardiolipin antibiodies (ACLA) be positive in
anti-phospholipid syndrome
what is there an increased risk of when ACLA is positive
thrombosis or pregnancy loss
what is c-ANCA/ anti- PR3 sensitive and specific for
granulomatosis with polyangitis (wegeners granulomatosis)
can ANCA be used to monitor disease activity
yes
how specific is p-ANCA/ anti-MPO and what is it associated with
less specific than c-ANCA/ anti-PR3
associated with microscopic polyangitis and churg strauss syndrome
fluctuates, used to monitor disease activity
what is the relevance of complement
low in immune complex vasculitis esp lupus nephritis
low in active lupus, used to monitor disease activity
what is the baseline imaging for early inflammatory arthritis- what would you expect to see
Xray hands and feet
expect to be normal- erosions may indicate poor prognosis
what is x ray of hands and feet used to diagnose
OA
what imaging for neck pain, especially in RA
cervical spine X ray
what is a cervical spine x ray looking for in RA flexion and extension views
atlanto-axial instability/ subluxation
why might a thoracic and lumbar spine x ray be done
to look for spondyloarthropathy changes
why would you do a High resolution CT chest
if suspect ILD as part of CTD/ RA
why would you do a joint ultrasound
to diagnose inflammatory arthropathy if not convinced by clinical synovitis
why would you do a MRI of the spine
non radiographic spondyloarthropathy- will show changes earlier than x ray
