Flow Cytometry: How Blood and Marrow Cells Are Analysed

Flow cytometry examines cells in a fluid stream, using light and fluorescent markers to distinguish cell populations by their features.

Cells from blood, bone marrow, lymph nodes, or another sample pass one at a time through a laser beam. Detectors record light scattered by each cell and signals from attached markers. The resulting pattern helps a laboratory describe which cell groups are present and how their features compare.

Flow cytometry is often used when clinicians need to characterise abnormal or immature blood-forming cells. It can help distinguish broad cell lineages and identify a pattern that supports classification of a blood or marrow disorder.

The test may be performed on a sample collected during a [Bone Marrow Biopsy](/treatments/diagnostics-and-staging/bone-marrow-biopsy/), or on blood or tissue collected in another way. Results are interpreted with the blood count, microscope findings, symptoms, and other laboratory or genetic tests.

The result depends on the sample's condition, the number and type of cells obtained, and the markers selected by the laboratory. A small or damaged sample may not answer every question. Some abnormal cells may not carry the expected markers, and closely related disorders can share overlapping patterns.

Flow cytometry does not replace a full pathology review. A clinician may need morphology, chromosome or molecular testing, imaging, or a repeat sample to reach a complete diagnosis and guide treatment.

Microscopic examination, immunohistochemistry, chromosome analysis, and molecular testing provide different kinds of information. The care team selects a combination based on the sample and the clinical question; these tests often complement one another.

Flow cytometry is a laboratory analysis of collected cells, not a treatment. A report may describe cell markers or populations without naming a final condition. The treating specialist combines those findings with the rest of your evaluation before explaining what they mean.

Ask when the sample was received, whether additional tests are pending, and which result will determine the next clinical decision. This can make a technical report easier to follow.

The instrument itself does not expose you to radiation. Any discomfort or bleeding risk comes from collecting the sample, such as a blood draw or marrow procedure, rather than from running flow cytometry. Follow the collection team's instructions about dressings and symptoms that need prompt attention.