Dihydrorhodamine Assay
Pronunciation: dy-HY-droh-ROH-duh-meen
Also written as: DHR — Dihydrorhodamine
A flow-cytometry-based functional test that measures the oxidative burst of neutrophils by detecting conversion of dihydrorhodamine 123 to fluorescent rhodamine 123, used to diagnose chronic granulomatous disease.
Full Definition
The dihydrorhodamine (DHR) assay has become the preferred method for evaluating NADPH oxidase function in clinical immunology laboratories. Neutrophils are loaded with the non-fluorescent probe dihydrorhodamine 123, stimulated with phorbol myristate acetate, and analysed by flow cytometry; normal cells convert DHR to brightly fluorescent rhodamine 123, whereas cells from patients with chronic granulomatous disease show little or no shift. Crucially, the DHR assay can also identify female carriers of X-linked CGD by demonstrating a bimodal fluorescence pattern. Editors working with immunodeficiency manuscripts must not conflate this functional assay with immunophenotyping panels, which assess surface markers rather than enzymatic activity. The abbreviation DHR is widely used in paediatric immunology literature.
Usage
Usage note: Do not hyphenate 'dihydrorhodamine'. Distinguish carefully from 'immunophenotyping' in edited text, as the two measure different neutrophil properties.
In Context
- "Dihydrorhodamine assay results demonstrated a classic bimodal pattern consistent with X-linked CGD carrier status in the patient's mother." — Genetic counselling report
- "The manuscript incorrectly labelled the dihydrorhodamine assay as an immunophenotyping technique; the editor corrected this to 'functional oxidative burst assay'." — Peer-review annotation