METHOD FOR DETECTING RARE EVENTS

This invention relates to a method for the detection of rare events which are events occurring at a frequency of less than one in 10 4 . It is particularly useful in detecting events at frequencies of one in 10 5 and one in 10 6 . The method employs one or more first markers that are specific for the rare event particle each of which are labeled with a dye having an emission wavelength distinguishable from the other(s). The method further employs one or more second markers that are specific for a majority of the remainder of the particles present in the cell sample but are negative for the rare event particle. The second markers all are labeled with the same dye. The second markers are collectively referred to as the exclusion color. By analyzing the particles for the presence of the first marker(s) and the absence of the second markers, rare events can be detected.