rheum diagnostics

Question 1

What blood tests do you do in rheumatology?

Answer 1

Full blood count FBC, urea & electrolytes (U & E), liver function tests (LFT), bone profile, erythrocyte sedimentation rate (ESR), C-reactive protein CRP

Question 2

What is seen on FBC of inflammatory arthritis?

Answer 2

Low Hb (anaemia) or normal, MCV normal, WCC usually normal, platelet normal or increased

Question 3

What is seen on FBC of osteoarthritis?

Answer 3

all normal

Question 4

What is seen on FBC of septic arthritis?

Answer 4

Hb usually normal (acute), MCV normal, WCC increased (neutrophilic leucocytosis), platelet count normal or high if marked inflammation

Question 5

What molecules are involved In urea & electrolytes? What can affect these?

Answer 5

• Urea, creatinine, sodium, potassium.
• High creatinine indicates renal problem.
• Rheum diseases can affect kidneys eg. SLE lupus nephritis, vasculitis to nephritis, chronic inflammation leads to high levels of Amyloid A (SAA) protein, deposition in organs leads to organ damage AA amyloidosis.
• NSAIDs can cause kidney problems

Question 6

What molecules are involved in LFT? When can these be deranged?

Answer 6

• Bilirubin, alanine aminotransferase (ALT), alkanine phosphatase ALP, albumin.
• DMARDs can cause liver damage (methotrexate need regular blood tests every 8wks).
• Low albumin can reflect liver or renal problems (increased leak in lupus nephritis).

Question 7

What is included in the bone profile? When can these be deranged?

Answer 7

• Calcium, phosphate, alkaline phosphatase ALP.
• Paget’s disease of bone causes high ALP because abnormal bone turnover (bone pain, growth pain, fractures.
• Osteomalacia (soft bones vitamin D deficiency): ALP normal or high, Calcium & phosphate normal or low.
• Osteoporosis (low bone density): normal

Question 8

What are ESR & CRP markers of? When are they deranged?

Answer 8

• Inflammation.
• ESR can be raised for other reasons eg. Elevated immunoglobulin levels, paraprotein (myeloma), anaemia, age.
• CRP more specific for inflammation.
• In SLE ESR more useful (ESR usually high but CRP normal), CRP only high in SLE if significant synovitis or inflammatory pleural or pericardial effusion.
• Low index for infection suspicion

Question 9

What antibodies are present in RA?

Answer 9

• Rheumatoid factor (not specific for RA, can be in hep C or generally).
• Anti-CCP antibodies: more specific than RF - associated with worse prognosis of RA

Question 10

What are anti-nuclear antibodies ANA? When is it deranged? When do you order it?

Answer 10

• Antibodies against nuclear component of cell.
• Non-specific, can be in healthy population in low level and increases with age, sometimes transiently after infection.
• High level ANA + correct clinical findings can point to autoimmune inflammatory diseases (SLE, sjorgen’s syndrome, scleroderma).
• Only order if suspect it because can lead to anxiety as is non-specific

Question 11

What are symptoms of SLE? FBC?

Answer 11

• Arthritis, skin rash, mouth ulcers, kidney disease, haematological, pleural effusion, pericardial effusion.
• Low lymphocytes and platelets

Question 12

What are symptoms of sjorgen’s syndrome?

Answer 12

Dry eyes, dry mouth due to destruction of salivary and lacrimal glands, extra-articular features

Question 13

What are symptoms of scleroderma?

Answer 13

Vasculopathy - raynauds, skin thickening, organ fibrosis

Question 14

What are symptoms of polymyositis?

Answer 14

Muscle inflammation, weakness, high creatine kinase

Question 15

What do you do if you suspect autoimmune connective tissue diseases? What diseases are included?

Answer 15

Order ANA.

-Includes SLE, sjorgens syndrome, scleroderma, polymyositis

Question 16

How is ANA interpreted? What does a negative & a positive test mean? What do you do if its is positive?

Answer 16

• Reported as maximal dilution at which still detectable eg. 1:80 weak, 1:1280 strong.
• Negative test rules out SLE but positive test doesn’t mean SLE, but suggestive with right clinical & lab features.
• If positive order other tests ENA (extractable nuclear antigens - panel of 5 antibodies)

Question 17

What is included in ENA (extractable nuclear antigens)?

Answer 17

Panel of 5 antibodies.
Ro (lupus & sjorgens), La (lupus & sjorgens), RNP (lupus or mixed connective tissue diseases), smith (lupus), jo-1 (polymyositis)

Question 18

What do dsDNA antibodies do? What are they associated with? Uses?

Answer 18

Antibodies against doubles stranded DNA, highly specific for lupus. Associated with renal involvement. Good for tracking lupus activity over time

Question 19

What happens to complement levels in lupus?

Answer 19

Low complement levels C3 & C4 in active lupus

Question 20

What is synovial fluid analysis? What are indications for it?

Answer 20

Aspirate fluid from joint. Diagnostic (for analysis) or therapeutic (relief or symptoms +/- concurrent steroid injection)

1. suspected septic arthritis (gold standard, send for culture/gram stain + sensitivities)
2. diagnose crystal arthritis

Question 21

What is seen in gout in synovial fluid analysis?

Answer 21

Under polarised light with microscope see needle shaped crystals negative birefringence

Question 22

What is seen in pseudogout in synovial fluid analysis?

Answer 22

under polarised light with microscope see rhomboid shaped crystals with positive birefringence

Question 23

What is seen in synovial fluid analysis for septic arthritis? What do you do?

Answer 23

Culture positive. Antibiotics + joint lavage

Question 24

What is seen in synovial fluid analysis for reactive arthritis? What do you do?

Answer 24

Synovial fluid sterile. No antibiotics or joint lavage

Question 25

What is 1st line imaging used in rheumatology and why?

Answer 25

X rays. Cheap, available

Question 26

What do CT scans offer?

Answer 26

more detailed bone imaging

Question 27

What do MRI scans offer? When are they best? disadvantages?

Answer 27

Best visualisation for soft tissue (tendons/ligaments). Best for spinal imaging (cord & nerve roots). Expensive & time consuming

Question 28

When is ultrasound best used?

Answer 28

Soft tissue. Good for smaller joints, less good for large/deep joints (knee/hip)

Question 29

What are x-ray features of osteoarthritis?

Answer 29

Joint space narrowing, osteophytes (bone spurs), subchondral cysts (bone cysts under cartilage), subchondral bony sclerosis (increased whitening)

Question 30

What do we see in imaging of RA? What imaging is used?

Answer 30

1. X-ray: Soft tissue swelling, peri-articular osteopenia, bony erosions (only in established disease - treat before permanent damage), joint space narrowing. 2. ultrasound - better for detecting synovitis. Synovial hypertrophy, increased blood flow seen as doppler signal, maybe erosions not seen in x-ray. Hands/wrists + clinical assessment for early RA 3. MRI - yes but expensive/time consuming

Question 31

What is seen in gout x-ray?

Answer 31

Juxta-articular rat bite erosions at MPTJ of toe

Question 32

What is seen in psoriatic x-ray?

Answer 32

Asymmetry, sparing of MCPJ but involvement of intraphalangeal joints

Question 33

Why can MRI be used for femoral head?

Answer 33

Avascular necrosis - bone infarction due to impaired blood supply