Rheumatology and diagnostics Flashcards
All possible bloods for rheumatology
FBC Urea+ Electrolytes Liver function tests bone profile Erythrocyte sedimentation rate C-reactive protein
FBC results for inflammatory arthritis
Hb - anaemia or normal
Normal MCV
Usually normal WCC
normal/increased platelet count
FBC results - osteoarthritis
all normal
FBC results - septic arthritis
Haemoglobin normal (too acute)
Normal MCV
Leukocytosis (neutrophilia)
Platelet count normal or raised (if with intense inflammation)
When is U+E useful for rheumatological diagnosis?
Multi-system rheum diseases can affect kidneys, e.g. SLE vasculitis, poorly controlled inflammatory disease
NSAIDs may cause kidney impairment (osteo)
how may poorly controlled inflammatory diseases affect the kidneys?
High levels of serum amyloid-A protein
SAA deposits in organs
AA amyloidosis
What are LFTs used for in rheumatology?
DMARDs can cause liver damage - patients on methotrexate need regular blood tests (8 weeks)
Low albumin can reflect leak from kidney e.g. SLE nephritis
What is included in bone profile?
Calcium
Phosphate
Alkaline Phosphatase (ALP- also in LFTs)
Name diseases identified through bone profile
Paget’s disease
Osteomalacia
Osteoporosis
Bone profile results - Paget’s disease
Very high ALP due to the disease being caused by abnormality of high bone turnover
Osteomalacia - bone profile results
ALP normal or raised
Ca and PO4 normal or low
Osteoporosis bone profile results
Calcium, PO4 and ALP normal
Non-pathological reason for raised ESR
Elevated immunoglobulin level
paraprotein
anaemia
tends to rise with age
Rule of thumb for SLE ESR/CRP
ESR high, CRP normal
except significant synovitis or inflammatory pleural or pericardial effusion
Auto antibodies indicated in rheumatoid arthritis
- Rheumatoid factor - nonspecific (hep C Sjorgen’s syndrome)
- Cyclic citrullinated peptides antibodies - specific, associated with worse prognosis
- ANAs
When to test for Antinuclear antibodies
in combination with correct clinical features of auto-immune connective tissue diseases
Due to false positives
Interpretation of ANA results
Negative test rules out SLE
Positive test does not discriminate for SLE, only suggestive is other clinical and lab features support diagnosis
If ANA positive, other tests to order for auto-immune connective tissue disorders
ENA (extractable nuclear antigens)
incl Ro, La, RNP, Smith, Jo-1
dsDNA antibodies - highly specific for Lupus
Features of Sjorgen’s syndrome
Dry eyes
dry mouth (due to destruction of salivarian and lacrimal glands)
Extra acticular features
SLE clinical features
Arthritis Skin rash (butterfly sunlight) mouth ulcers kidney disease haematological pleural effusion pericardial effusion
Polymyositis clinical features
Muscle imflammation
weakness
high creatine kinase (CK)
Scleroderma clinical features
vasculopathy (especially Raynaud’s)
skin thickening
organ fibrosis
Indications for joint aspiration
- Diagnostic
2. Theraputic
Synovial fluid analysis use in diagnosis
septic arthritis - gold standard, send for MC&S, identify organism and guide antibiotic choice
crystal arthritis - birefringence of crystals
Gout vs pseudo-gout joint aspiration findings
Gout - needle-shaped negative birefringence
Pseudo-gout - rhomboid-shaped crystals with Positive birefringence
Reactive arthritis vs septic arthritis
reactive - sterile fluid culture, no antibiotic therapy or joint lavage
septic - positive fluid culture, antibiotic therapy, joint lavage
Imaging modalities - rheumatology
X-ray first line
CT
MRI - soft tissues, spinal
ultrasound smaller joints, soft tissues
Osteoarthritis X-ray findings
joint space narrowing
subchondral bony sclerosis
Osteophytes
Subchondral cysts
Rheumatoid arthritis imaging
X-ray for soft tissue swelling, peri-articular osteopenia, bony erosions,
Ultrasound - for synovitis (synovial hypertrophy, increased blood flow)
MRI
gout features on x ray
rat bite erosions
rheumatoid arthritis vs osteoarthritis X ray differences
joint space narrowing - RA OA subchondral sclerosis - OA osteophytes - OA osteopenia - RA bony erosions - RA
what are bouchards nodes
osteophytes at proximal inter-phalangeal joints (OA)
what are Heberdens nodes?
osteophytes at distal interphalangeal joints (OA)
