FLAER

FLAER, in the context of laboratory diagnostics, stands for fluorescein-labeled aerolysin. It is a fluorescent probe used in flow cytometry to detect glycosylphosphatidylinositol (GPI) anchors on cell surfaces. FLAER is a derivative of the bacterial toxin aerolysin that has been rendered non-pore-forming and conjugated to a fluorophore, enabling binding without lysing cells.

Its primary clinical application is the detection and characterization of paroxysmal nocturnal hemoglobinuria (PNH). PNH arises from clonal populations of blood cells that lack GPI-anchored proteins. In a typical FLAER‑based assay, cells are stained with FLAER and with monoclonal antibodies against key GPI-anchored proteins (often including CD55 and CD59) along with lineage markers. Flow cytometry then identifies FLAER-negative populations among granulocytes, monocytes, and, when feasible, red cells. The combination of FLAER negativity and loss of GPI-anchored proteins indicates PNH clones. FLAER-based assays are known for high sensitivity, capable of detecting very small populations of GPI-deficient cells, depending on sample quality and instrument performance.

FLAER is commonly integrated into diagnostic panels for PNH and is used in conjunction with other markers to provide corroborative evidence across cellular lineages. It is typically employed in modern clinical laboratories equipped for multi-parameter flow cytometry and requires appropriate controls and gating strategies. While the reagent is widely available from major suppliers, results depend on sample handling, staining protocol, and instrument settings.