Rheumatology Diagnostics Flashcards
What are the different categories in rheumatology diagnostics?
Bloods
Joint (synovial) fluid analysis
Imaging
What blood tests should you order for a patient with painful joints? (Basic)
Full blood count (FBC) Urea and electrolytes (U&E) Liver function tests (LFT) Bone profile Erythrocyte sedimentation rate (ESR) C-reactive protein (CRP)
What should you do before ordering tests?
Do I need these tests?
Can we make a diagnosis on history and examination alone
e.g. osteoarthritis of the knee
What are the three types of arthritis?
Osteo
Inflammatory
Septic
What should be done first when ordering bloods?
Basic tests before ‘fancy’ ones
What are the main components of a FBC?
Hb
MCV
PLT
WCC
What are the Hb readings for different arthritis types?
Inflammatory - low or normal
Osteo - normal
Septic - usually normal
What are the MCV readings for different arthritis types?
All normal
What are the WCC readings for different arthritis types?
Inflammatory - normal
Osteo - normal
Septic - high
What are the PLT readings for different arthritis types?
Inflammatory - normal or high
Osteo - normal
Septic - normal or high
What is looked in U+E’s?
Urea
Creatinine
Sodium
Potassium
What does high Cr indicate?
worse renal clearance (indicating kidney problem)
What is the relevance of Cr in rheumatology?
Rheumatological diseases can affect the kidneys
Give examples of rheumatological diseases that manifest in kidneys?
a) Systemic lupus erythematous (SLE) -> lupus nephritis
b) Vasculitis -> nephritis
c) Chronic inflammation in poorly controlled inflammatory disease
What happens in poorly controlled inflammatory disease?
high levels of serum amyloid A (SAA) protein -> SAA deposits in organs (AA amyloidosis)
How else might rheumatological disease cause kidney malfunction?
Non-steroidal anti-inflammatory drugs (NSAIDs) (eg ibuprofen) can cause kidney impairment
What is looked at in LFTs?
Bilirubin
Alanine aminotransferase (ALT)
Alkaline phosphatase (ALP)
Albumin
What is the relevance of doing LFTs?
Disease modifying anti-rheumatic drugs (DMARDs) (eg methotrexate) can cause liver damage.
Key point: patients on methotrexate need regular blood tests (eg every 8 weeks).
What can low albumin indicate?
can either reflect problem of synthesis (in liver) or problem of leak from kidney (eg in lupus nephritis)
What is done on a bone profile?
Calcium
Phosphate (PO4)
Alkaline phosphatase (ALP)
nb also in LFTs – confusingly the source of ALP can be bone OR liver
In which disease is high ALP seen?
Paget’s disease of bone: ALP ↑↑
Paget’s = disease caused by abnormality of high bone turnover.
What is the bone profile of osteomalacia?
ALP normal or ↑, Ca and PO4 normal or ↓
What is the bone profile of osteoporosis?
usually calcium, PO4 and ALP normal
Aside from inflammation, what can cause a high ESR?
- Elevated immunoglobulin level
- Paraprotein (myeloma)
- Anaemia
- Tends to rise with age
What is usually more specific in inflammation CRP or ESR?
CPR