Autopsy of a cell

Staining with annexin V, which detects the externalization of phosphatidylserine on cells, is a widespread method for the assessment of cell death, and in particular, apoptosis.1 Although additional assays are important for demonstrating apoptosis, many studies use annexin V staining in isolation and directly equate annexin V positivity with apoptosis. Is this a problem? Although cells undergoing apoptosis externalize phosphatidylserine, describing annexin V-positive cells as apoptotic can be misleading. Here we briefly highlight strengths and limitations of assessing apoptosis using annexin V staining.