Flow Cytometry - HLA B27 - EDTA
Also Known As
* HLA B27 Typing
* Human Leukocyte Antigen B27 Test
* HLA B27 by FCM
* Ankylosing Spondylitis Gene Test
* Spondyloarthritis Gene Test
* B27 Antigen Test
Test Parameters Included
- HLA-B27 Antigen Expression (%) on Peripheral Blood Lymphocytes via Flow Cytometry
- Pathologist Immunogenetics Remark - correlated with spondyloarthropathy clinical reference
Department
Methodology
Flow cytometry is a powerful, rapid, and accurate technique used in a clinical laboratory to analyze the physical and chemical characteristics of a population of cells, such as those found in a blood sample. For the detection of HLA-B27, the process involves the following steps:
* Sample Preparation: A whole blood sample is collected and a portion of it is prepared for analysis. The red blood cells are typically lysed (broken apart) to isolate the white blood cells (leukocytes), which express the HLA-B27 antigen on their surface. * Antibody Staining: The isolated white blood cells are then incubated with a specific monoclonal antibody that is designed to bind exclusively to the HLA-B27 antigen. This antibody is conjugated (tagged) with a fluorescent dye (a fluorochrome). * Flow Cytometer Analysis: The stained cells are then suspended in a fluid and injected into a flow cytometer. This instrument hydrodynamically focuses the cells into a single-file stream, which passes through a laser beam one cell at a time. * Signal Detection: When the laser strikes a cell, the fluorescent dye on the antibody, if present, is excited and emits light at a specific wavelength. Detectors in the flow cytometer measure this emitted light. The intensity of the fluorescence signal is directly proportional to the amount of HLA-B27 antigen present on the cell surface. * Data Analysis: The flow cytometer also measures other properties of the cells, such as their size and granularity. This data is collected for thousands of cells and is then analyzed by a computer program. By gating (isolating) specific cell populations (e.g., lymphocytes), the system can accurately determine the percentage of cells that are "positive" for the HLA-B27 antigen, providing a highly specific and sensitive result.
Sample Required
* Preferred Sample: Whole Blood in a Lavender-top (EDTA) tube or Green-top (Heparin) tube. The EDTA or heparin prevents the blood from clotting, which is essential for flow cytometry. * Alternate Sample: Bone Marrow Aspirate (BMA), though whole blood is the more common sample type for this test. * Volume: Typically, a small volume (e.g., 2-4 mL) of whole blood is sufficient. * Handling and Stability: The sample should be kept at room temperature (ambient temperature) and processed as soon as possible, ideally within 24-48 hours. Refrigerated or frozen samples are often unacceptable as they can alter the cell morphology and the integrity of the surface antigens, leading to inaccurate results.
Preparation
Schedule Report
24-48 Hours
Emergency Report
Yes
Frequently Asked Questions
What is the HLA B27 test for?
The HLA B27 test checks for the presence of a specific protein (antigen) on your white blood cells. This antigen is strongly associated with an increased risk of developing certain autoimmune inflammatory diseases, particularly ankylosing spondylitis.
What is the difference between this test and a PCR test for HLA B27?
The Flow Cytometry method detects the HLA B27 protein on the cell surface. PCR (Polymerase Chain Reaction) is a molecular method that detects the HLA B27 gene itself. Both are highly accurate, but flow cytometry is often faster and less expensive.
Do I need to fast or prepare in any special way for this test?
No, no special preparation is needed. You can eat and drink as you normally would.
How long will it take to get my results?
The report will typically be available within 24-48 hours.
What does a "Positive" result mean?
A positive result means you have the HLA-B27 antigen. This indicates you have a higher genetic risk for certain inflammatory conditions. It is not a definitive diagnosis, as many people with this antigen never develop a disease. Your doctor will interpret this result alongside your symptoms and other test findings.
What does a "Negative" result mean?
A negative result means the HLA-B27 antigen was not found. While this makes an HLA-B27-associated disease less likely, it doesn't completely rule it out, as a small number of patients with these diseases are HLA-B27 negative.
Is a positive result dangerous?
A positive result is not dangerous in itself. It simply indicates a genetic predisposition. It is a marker for your doctor to consider when evaluating your symptoms. It does not mean you will definitely get a disease.
What kind of sample is required for this test?
A small sample of whole blood is required, typically collected in a lavender-top (EDTA) or green-top (Heparin) tube. Bone Marrow Aspirate can also be used as an alternate sample.
Why is it important to use a fresh sample?
The flow cytometry method relies on the integrity of the cells and the antigens on their surface. Refrigeration or freezing can damage these cells and antigens, leading to inaccurate results. The sample should be kept at room temperature and processed promptly.
Can this test be used to monitor disease progression?
No, the HLA B27 test is a diagnostic test to determine genetic predisposition. It is not used to monitor disease activity or progression. For that, other inflammatory markers like ESR and CRP are more useful.
Test Description
Test Code
FCM36 / H40
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