HLA-B27
Last updated: November 9, 2014
CPT Code: 86812
Description: HLA-B27, one of the HLA-B alleles, is expressed on all human cells and is involved in presentation of antigen to CD8+ T cells. HLA-B27 is often associated with spondyloarthropathies such as ankylosing spondylitis, reactive arthritis, psoriatic arthritis, and enteropathic arthritis.
Method: Collect 15 mL of blood into tubes containing acid-citrate-dextrose solution B and mix to avoid coagulation. Do not refrigerate or freeze. HLA-B27 may be detected by a microcytotoxicity assay in which mononuclear cells are exposed to test antiserum and complement. HLA-B27 also can be detected by flow cytometry using HLA-B27–specific antibodies.
Normal Values: HLA-27 is a normal gene found in as many as 8% of normal individuals (6%–8% of whites, 3%–4% of African Americans, and 1% of Asians).
Increased in: HLA-B27 is unifying feature to the disorders grouped under spondyloarthritis. The frequency of this allele in these disorders is shown below (Table). HLA-B27 positivity is associated with a propensity for axial disease (spondylitis) and uveitis. HLA-B27 positive individual have an earlier onset of spinal symptoms, less delay in diagnosis, greater axial inflammation on imaging and a lower frequency of psoriasis. The actual risk of an HLA-B27–positive person developing ankylosing spondylitis is estimated to be 1% to 2%. Only 20% of HLA-B27-positive individuals infected with arthritogenic bacteria (Salmonella, Shigella) may develop a reactive arthropathy. Also, only 20% of HLA-B27–positive first-degree relatives of HLA-B27– positive patients with spondylitis develop ankylosing spondylitis. HLA-B27 positivity may correlate with more aggressive disease in reactive arthritis, but not in ankylosing spondylitis.
| Table. Population Frequency of HLA-B27 | ||||
| Population | Frequency of HLA-B27 (%) | |||
|---|---|---|---|---|
| Ankylosing spondylitis | 90 | |||
| Ankylosing spondylitis with uveitis/aortitis | > 95 | |||
| Reactive arthritis (Reiters) | 75-80 | |||
| Juvenile spondylitis | 70 | |||
| Psoriatic arthritis | ||||
| Peripheral arthritis | < 10 | |||
| Spondylitis | 50 | |||
| Enteropathic arthritis | ||||
| Peripheral arthritis | < 15 | |||
| Spondylitis | 50 | |||
| Acute anterior uveitis | 50 | |||
| Aortic insufficience with heart block | 80 | |||
| General population | ||||
| Whites | 6-8 | |||
| African Americans | 3-4 | |||
| Asians | 1 | |||
Indications: HLA-B27 assay is used infrequently as a diagnostic test in suspected cases of spondyloarthropathy. It should not be routinely ordered for evaluation or screening of patients with low back pain because the prevalence of HLA-B27 may be as high as 8%, yet the prevalence of spondyloarthropathy is perhaps one per 1,000 individuals. Random use of this test is more likely to yield more false-positive than true-positive results. It is diagnostically valuable when applied to patients with inflammatory low back pain – B27+ in this scenario increases the odds of ankylosing spondylitis from 15% to >50%. Others who may benefit from HLA-B27 testing are patients with an “incomplete” syndrome manifest as few spondyloarthropathy features (e.g., enthesitis, plantar fasciitis, uveitis, nail pitting) without inflammatory back pain or inflammatory oligoarthritis. B27 testing is of no value when the probability of disease is either very low or very high.
Cost: $80–110.
BIBLIOGRAPHY
Khan MA. Update on spondyloarthropathies. Ann Intern Med. 2002;136:896-907. PMID: 12069564
Chung HY, Machado P, van der Heijde D, et al. HLA-B27 positive patients differ from HLA-B27 negative patients in clinical presentation and imaging: results from the DESIR cohort of patients with recent onset axial spondyloarthritis. Ann Rheum Dis. 2011;70:1930-6. PMID: 21803752
Gardner GC, Kadel NJ. Ordering and interpreting rheumatologic laboratory tests. J Am Acad Orthop Surg 2003;11:60–67.PMID:12699372
