Flow cytometric measurement of platelet-associated immunoglobulin.

The measurement of PAIg has been made very difficult by a number of technical and biological problems as outlined above. The flow cytometric approach helped to solve a number of problems. It appears to be at least as good as other techniques and better in many ways. However, it must be recognized that there remain unsolved problems. Flow cytometry has the great advantage of revealing the presence of previously unsuspected subpopulations. There is no question that such subpopulations exist, and that they are responsible, at least in part, for much of the difficulty that PAIg assays has encountered. However, at the moment we understand very little about how these subpopulations arise and what their significance is. When we can explain them it seems likely that our understanding of immune thrombocytopenia will be dramatically improved, and with it, the clinical utility of the PAIg measurement.