Investigations

Question 1

Investigations done in rheumatic disease.

Answer 1

Hb

Platelets

Neutrophils

Lymphocytes

U&Es

Uric acid

LFTs

CK, ALT and LDH

Question 2

Advantages of ESR as an inflammatory marker.

Answer 2

Widely understood

Well established in diagnosis and monitoring of GCA

Question 3

Disadvantages of ESR as an inflammatory marker.

Answer 3

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

Question 4

Advantages of PV as inflammatory marker.

Answer 4

Automatable

Sensitive

Not affected by anaemia

Measurement can be made on stored blood samples

Question 5

Disadvantages of PV as inflammatory marker.

Answer 5

Not widely used and therefore a lack of familiarity with interpretation.

Question 6

Advantages of CRP as inflammatory marker.

Answer 6

Automatable

Very sensitive

Not affected by haematocrit

Measurement can be made on stored blood samples

Question 7

When to request investigation of autoantibodies?

Answer 7

Only request if there is a high clinical suspicion of a particular disease.

False positives are common and cause confusion!

Question 8

Auto-antibodies for RA.

Answer 8

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.

Question 9

Answer 9

Question 10

C-ANCA - antibody to proteinase-3 indicative of…

Answer 10

GPA

Infection

Neoplasia

Question 11

P ANCA - antibody to MPO indicative of…

Answer 11

Microscopic polyangiitis

Infection

Neoplasia

Question 12

HLA-B27 is strongly associated with?

Answer 12

Ankylosing spondylitis

Question 13

Why is urinalysis important in rheumatic disease?

Answer 13

Presence of protein and/or blood on a urine dipstick.

Suggestive of SLE and vasculitis

Question 14

Synovial fluid analysis in rheumatic disease.

Answer 14

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.

Question 15

Biopsies done in rheumatic disease.

Answer 15

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

Question 16

What can nerve conduction studies be useful for?

Answer 16

Confirm peripheral nerve entrapment such as CTS

Question 17

What might electromyography be useful for?

Answer 17

Record spontaneous and voluntary muscle activity and has characteristic abnormalities in myositis.

Question 18

What imaging might be done in rheumatic disease?

Answer 18

X-ray

USS - synovitis and erosions in RA and PsA, tenosynovitis

MRI - knees and shoulders for meniscal, ligament tears and rotator cuff tears.

Question 19

DXA useful for?

Answer 19

Evaluation of osteoporosis.

Estimates bone mineral density at different sites.

T score indicated BMD of the patient compared to a normal person of same age and sex.

Osteoporosis is diagnosed when the T score is less than 2.5 standard deviations below the mean.