PROFICIENCY TESTING IN CLINICAL CYTOGENETICS - A 6-YEAR EXPERIENCE WITH PHOTOGRAPHS, FIXED CELLS, AND FRESH BLOOD

The College of American Pathologists and the American Society of Human Genetics offer a proficiency testing program in clinical cytogenetics . Two hundred twenty-five laboratories now provide data for this surve y, which was begun in 1986. Challenges have consisted of photographed metaphases, fixed lymphoblastoid cell suspensions, fresh peripheral bl ood, and disarranged karyotypes. The ''correct'' response was based on 80% or greater consensus among either the referees or the participant s. Referee laboratories performed better than participants. More labor atories were able to report accurate recognition of abnormalities by u sing a coded list than could write the interpretation in standardized nomenclature. Deletions, unbalanced translocations, and inversions wer e more difficult challenges than balanced translocations or trisomies. Prenatal and lymphocyte challenges were more likely to result in cons ensus than were bone marrow challenges. Participants performed best on whole-blood challenges. Fixed cell suspensions were less satisfactory . Excellent quality case material is essential for a successful challe nge. A grading system has been devised to separate artifacts of the su rvey process from proficiency variables.