Proficiency testing in clinical cytogenetics. The 1986 experience of the College of American Pathologists.

In 1986, the College of American Pathologists introduced a proficiency testing program in cytogenetics entitled "survey CY." Approximately 140 laboratories actively participated. The survey consisted of 20 cytogenetic cases sent to the participants in quarterly shipments of five challenges each. Photographic negatives of metaphases were the primary medium studied. The results reported by the participants were highly concordant for the determination of modal chromosome count and sex chromosome designation. More than 90% of the participants correctly identified the following abnormalities: trisomies 8, 13, 18, 21, and X; monosomy X; t(9;22); t(8;21); der(2) t(2;?); and 5p-. Abnormalities A fra(X)(q27), t(5;11), inv(16), and t(15;17) were correctly identified by more than 80%, 70%, 70%, and 60% of the participants, respectively. The participants had the most difficulty with diagnoses that involved photographs of high-resolution chromosome banding. The 1986 survey was not graded, but the 1987 cytogenetics survey will be scored on those challenges where there is at least 80% consensus among the participants.