investigations

Last edited 12/2020 and last reviewed 12/2020

Investigations

• WBC - usually raised
• ESR and CRP - usually raised
• hypergammaglobulinaemia
• rheumatoid factor - absent

Imaging for suspected psoriatic arthritis and other peripheral spondyloarthritides (1)

• offer plain film X-ray of symptomatic hands and feet for people with suspected peripheral spondyloarthritis in these areas
• If a diagnosis cannot be made from the plain film X-ray, consider ultrasound of:
• the hands and feet to assess for joint involvement
• suspected enthesitis sites
• consider plain film X-rays, ultrasound and/or MRI of other peripheral and axial symptomatic sites
• interpret a positive HLA-B27 result as increasing the likelihood of peripheral spondyloarthritis.
• if a diagnosis of peripheral spondyloarthritis is confirmed, offer plain film X-ray of the sacroiliac joints to assess for axial involvement, even if the person does not have any symptoms.

• radiology - characteristic features include (2):
  • joint erosions and joint space narrowing
  • bony proliferation including periarticular and shaft periostitis,
  • osteolysis including "pencil in cup' deformity,
  • acro-osteolysis
  • ankylosis,
  • spur formation,
  • spondylitis

Erosive changes of the DIP seen in radiography may be used as both a sensitive and specific diagnostic feature of psoriatic arthritis (2).

Reference:

• NICE (2017). Spondyloarthritis in over 16s: diagnosis and management
• American Academy of Dermatology 2008. Guidelines of care for the management of psoriasis and psoriatic arthritis - Section Psoriatic arthritis: Overview and guidelines of care for treatment with an emphasis on the biologic