The HLA-B27 genotyping test is a genetic test used to identify the presence of the HLA-B27 allele, a specific gene variant in the human leukocyte antigen (HLA) system. This allele is associated with a higher risk of developing certain autoimmune and inflammatory conditions, particularly ankylosing spondylitis and other spondyloarthropathies.

• Positive HLA-B27: Indicates a higher genetic risk for conditions like ankylosing spondylitis, reactive arthritis, juvenile idiopathic arthritis, and other related autoimmune disorders. However, not all individuals with HLA-B27 develop these conditions. The presence of HLA-B27 increases the likelihood but is not solely diagnostic.
• Negative HLA-B27: A negative result reduces but does not completely eliminate the risk of developing HLA-B27-associated disorders. Other genetic and environmental factors can still contribute to disease development.

• HLA-B27 Negative: This is considered the "normal" or typical result. Most people do not have the HLA-B27 allele.
• HLA-B27 Positive: This is outside the normal range but is relatively common in certain populations. About 6-10% of the general population carries the HLA-B27 allele, though prevalence varies by ethnicity.

• Positive Result: If the test is positive for HLA-B27, it suggests an increased risk for HLA-B27-associated diseases. This result should be interpreted in the context of clinical findings and other diagnostic tests. A positive result does not confirm the presence of a disease but may prompt further investigation or monitoring.
• Negative Result: A negative result suggests a lower likelihood of HLA-B27-associated conditions but does not rule them out completely.

• Blood Sample: The most common sample type for HLA-B27 genotyping is a blood sample. Blood is drawn from a vein, usually from the arm.
• Buccal Swab: Sometimes, a buccal swab (a sample of cells from the inside of the cheek) can also be used for genotyping.