HLA-B27 typing

What it measures

Detects the HLA-B27 gene/antigen, strongly associated with spondyloarthritis. It supports diagnosis of ankylosing spondylitis in patients with inflammatory back pain.

Specimen and preparation

• Specimen: EDTA whole blood
• Tube: Lavender top
• Preparation: Do not freeze; flow cytometry needs intact cells, so deliver within 24–72 h at room temperature (or refrigerated if the lab allows).

Reference range

Reference ranges differ between laboratories, methods and populations. Always use the range printed on your own lab report.

Causes of high values

• Ankylosing spondylitis (about 90%)
• Reactive arthritis, psoriatic and enteropathic arthritis
• Acute anterior uveitis
• About 6–8% of healthy people carry it

Method

Flow cytometry or PCR (sequence-specific primers)

Good to know

A positive result alone does not diagnose disease; it must be read with symptoms and imaging.

Related tests