Table 3.

Reportable quantities in EV analysis and relevant calibrators and standards

Measurement	Derived from	Calibrator or standards	Reportable Values
EV concentration	Number of events detected per volume of fluid	Beads of known concentration to calibrate sample flow rate	EVs/uL
EV size	Signal intensity	EV preps of known size (determined by orthogonal method, such as NTA or TRPS) or by calculation using standards of known size and refractive index.	Diameter, surface area, or volume of detected EVs
EV fluorescence positive concentration	Number of events detected above a threshold per volume of fluid	Beads of known concentration to calibrate sample flow rate plus negative control sample to set threshold for positivity	Positive EVs/uL above a threshold
EV fluorescence brightness/antibody number	Signal intensity	Standard particles with calibrated intensity or antibody capture capacity	Mean fluorescence intensity (MESF) or antibodies bound per EV