CD64 is the high-affinity Fc-gamma receptor.
The CD64 index compares fluorescent readings with neutrophils versus coated latex beads.
CD64 =
= (fluorescent readings for neutrophils) / (fluorescent readings for coated beads)
Controls include readings for:
(1) lymphocytes (index should be < 1)
(2) monocytes, as identified with CD163 (index should be > 3)
Sepsis or severe bacterial infections are associated with a neutrophil CD64 index > 1.19.
An infected patient may have a CD64 index <= 1.19 but this tends to be seen in a localized infection.
Limitations:
• Most evaluations involve bacterial infections. It may function differently in a patient with fungemia.
• Most studies evaluate patients from a general population. Performance may be different in a patient with a neutrophil disorder.
