Rheumatology Diagnostics Flashcards

Question

Why is it important to order the ANA test indiscriminately?

Answer 1

It is non-specific If ordered on everyone with joint pain, there will be many false positives Therefore only ordered for suspected autoimmune connective tissue disease

Answer 2

``` SLE / lupus = Arthritis Skin rash Mouth ulcers Kidney disease Haematological Pleural effusion Pericardial effusion ``` Sjogren's syndrome (some relation to lupus - destruction of the salivary and lacrimal glands) Dry eyes Dry mouth Extra-articular features Scleroderma = Vasculopathy (esp. Raynaud's) Skin thickening Organ fibrosis Polymyositis = Muscles inflammation Weakness High CK (creatinine kinase)

Answer 3

1. ANA test either says negative, or it gives a number The number refers to ANA presence in maximal dilution: e.g. 1:80 means ANA still detectable after 80 dilutes (weak), 1:320, 1:640, 1:1280 (strong) 2. Negative test rules out SLE (lupus) 3. BUT positive test does not necessarily mean SLE - but supports diagnosis if present with clinical features

Answer 4

ANA = screening test Therefore must narrow down which auto-antibody it is causing the positive ANA So next do ENA (extractable nuclear antigens): a panel of 5 autoantibodies

Answer 5

5 autoantibodies - positive in: ``` Ro - Lupus or Sjogrens syndrome La - Lupus or Sjogrens syndrome RNP - Lupus or mixed connective tissue disease Smith - Lupus Jo-1 - Polymyositis ```

Answer 6

Double stranded DNA antibodies Highly specific for lupus, associated with renal involvement, useful for tracking lupus activity over time

Answer 7

Complement levels C3 and C4 - tend to go down as the lupus is active

Answer 8

1. Aspirate joint to get fluid | 2. Examine fluid under a microscope

Answer 9

1. Diagnostic = to obtain synovial fluid for analysis 2. Therapeutic = to relief symptomsby taking off the fluid (+/- concurrent steroid injection ONLY if confident there is no infection present)

Answer 10

1. Suspected septic arthritis = - gold standard for diagnosis - send for MC&S - enables causative organism to be identified - sensitivities from culture guide antibiotic choice 2. Diagnosing crystal arthritis

Answer 11

Examined under a microscope using polarised light ``` Gout = needle shaped crystals with negative birefringence Pseudogout = rhomboid shaped crystals with positive birefringence ```

Answer 12

Septic VS reactive arthritis = Positive VS sterile synovial fluid Yes VS no antibiotic therapy treatment Yes for large joints VS no joint lavage

Answer 13

X-rays = first line, cheap, widely available CT scans = more detailed bony imaging MRI scans = Best visualization of soft tissue structures like tendons and ligaments Best for spinal imaging: can see spinal cord and exiting nerve roots Expensive and time-consuming USS (ultrasounds) = Like MRI can visualize soft tissue structures. Good for smaller joints, less good for deep/large joints like knee or hip

Answer 14

Joint space narrowing - bone touching bone Subchondral bony sclerosis - increased white appearances on the x-ray Osteophytes - extra bone growths Subchondral cysts - bone cycts under the cartilage

Answer 15

X-rays USS (ultrasound scan) MRI

Answer 16

Soft tissue swelling - can barely been seen on x-rays as they predominantly are limited to view bones Peri-articular osteopenia Bony erosions Ulnar drift of fingers

Answer 17

Bony erosions occur only in established disease - the aim of modern therapy is to treat EARLY before erosions (permanent damage) has occurred Therefore, x-rays are not useful in early rheumatoid and should not be falsely reassured that the patient does not have RA

Answer 18

Much better at detecting synovitis changes - ``` Synovial hypertrophy (thickening) Increased blood flow (seen as doppler signal) May detect erosions not seen on plain X-ray ```

Answer 19

Much better test for detecting synovitis USS (usually of hands and wrists) can be performed alongside clinical assessment in a dedicated early arthritis clinic

Answer 20

Often do not provide significantly more info than USS | Time consuming and expensive

Answer 21

RA VS OA = ``` Yes VS Yes joint space narrowing No VS Yes subchondral sclerosis No VS Yes osteophytes Yes VS No osteopenia Yes VS No bony erosions ```

Answer 22

RA = Erosion and resorption of the distal ulna Marked erosions at the MCPJs (metacarpophalangeal joints) Ulnar deviation / ulnar drift of fingers OA = MCPJs spared Clean joints Changes at DSPJs with increased whitening (sub-controlled sclerosis)

Answer 23

X-rays are usually normal during the first few attacks of gout But over time (many years), radiographs show juxta-articular ‘rat bite’ erosions at the MTPJ of the great toe

Answer 24

Asymmetry of the joints involved Sparing of the MCPJs Involvement / Erosions of the IPJs Pencil and cup deformities at IPJs

Answer 25

X-rays may turn up normal, but symptoms continue to persist, therefore next step is to do an MRI e.g. 5OF Acute onset of L hip (groin) pain, no trauma Constant pain, worsening with weight bearing PMH of SLE in remission The hip X-ray turned up completely normal HOWEVER the hip MRI showed reduced and painful internal rotation of the L hip (could progress onto avascular necrosis of the femoral head)