White blood cell differential: a call for standards.

The technology available to count and classify white blood cells has rapidly evolved from 1974 to the present. Two previous conferences, the College of American Pathologists Aspen Conference (1977) and Blood Cells in Paris (1980) have considered the technical and medical questions raised by these new technologies. The National Committee for Clinical Laboratory Standards (NCCLS) met in November 1984 to continue this debate and to provide a forum for manufacturers, laboratory directors, and government regulatory agencies to establish standards for the performance of the white blood cell differential. The development and clinical evaluation of the current commercially available white cell differential counters is reviewed as background for this meeting.