Investigations Flashcards
Investigations done in rheumatic disease.
Hb
Platelets
Neutrophils
Lymphocytes
U&Es
Uric acid
LFTs
CK, ALT and LDH
Advantages of ESR as an inflammatory marker.
Widely understood
Well established in diagnosis and monitoring of GCA
Disadvantages of ESR as an inflammatory marker.
No technique for calibration to test for accuracy.
Poor reproducibility
Test takes 1 hour
Must be carried out within 4 hours of blood sampling
Rises with anaemia
Advantages of PV as inflammatory marker.
Automatable
Sensitive
Not affected by anaemia
Measurement can be made on stored blood samples
Disadvantages of PV as inflammatory marker.
Not widely used and therefore a lack of familiarity with interpretation.
Advantages of CRP as inflammatory marker.
Automatable
Very sensitive
Not affected by haematocrit
Measurement can be made on stored blood samples
When to request investigation of autoantibodies?
Only request if there is a high clinical suspicion of a particular disease.
False positives are common and cause confusion!
Auto-antibodies for RA.
Rheumatoid factor - antibody directed against the Fc portion of human IgG.
RF+ patients tend to have more severe disease.
Anti-cyclic citrullinated peptide antibody (anti-CCP) is more specific for RA than RF.
C-ANCA - antibody to proteinase-3 indicative of…
GPA
Infection
Neoplasia
P ANCA - antibody to MPO indicative of…
Microscopic polyangiitis
Infection
Neoplasia
HLA-B27 is strongly associated with?
Ankylosing spondylitis
Why is urinalysis important in rheumatic disease?
Presence of protein and/or blood on a urine dipstick.
Suggestive of SLE and vasculitis
Synovial fluid analysis in rheumatic disease.
Most important investigation in septic arthritis and crystal arthropathy.
Sent for gram stain and culture, before antibiotic treatment if possible.
Polarised light microscopy can be done to distinguish between gout and pseudogout.
Biopsies done in rheumatic disease.
Temporal artery biopsy for GCA.
Muscle biopsy - polymyositis or dermatomyositis
Skin biopsy in vasculitis, dermatomyositis, SLE
Lip/salivary gland - Sjögrens
Lymph node - SLE to rule out lymphoma or TB
Synovial biopsy for rare tumours or infections.
Sural nerve - vasculitis with mononeuritis multiplex/peripheral neuropathy
Renal biopsy - vasculitis, SLE