Misinterpretation of solid sphere equivalent refractive index measurements and smallest detectable diameters of extracellular vesicles by flow cytometry
Edwin van der Pol, Ton G. van Leeuwen, Xiaomei Yan
Abstract
Flow cytometers are utilized to characterize single submicrometer particles in biofluids, such as extracellular vesicles (EVs) and viruses. However, because calibration of the optical signals measured by flow cytometers requires optical modelling and valid assumptions, which are not straightforward, statements in the literature about the sensitivity of flow cytometers are often either lacking or incorrect. In this Letter, we explain why measurement artifacts and a statistical artefact cause an overestimation of the refractive index of EVs as derived by Brittain et al. Because these artifacts lead to conclusions that are not supported by the data, we re-analyzed the data of Brittain et al. to rectify statements about the sensitivity of their flow cytometer.