1458 Arch Pathol Lab Med—Vol 126, December 2002 Proficiency Testing for Laboratories Performing FISH—Mascarello et al Proficiency Testing for Laboratories Performing Fluorescence In Situ Hybridization With Chromosome-Specific DNA Probes JamesT. Mascarello, PhD; Arthur R. Brothman, PhD; Keri Davison, BS; Gordon W. Dewald, PhD; Marille Herrman, MD, PhD; Danette McCandless, MD; Jonathan P. Park, PhD; Diane L. Persons, MD; Kathleen W. Rao, PhD; Nancy R. Schneider, MD, PhD; Gail H.Vance, MD; Linda D. Cooley, MD; for the Cytogenetics Resource Committee of the College of American Pathologists and American College of Medical Genetics ● Objective.—To assess laboratory performance, use, and limitations in the joint College of American Pathol- ogists and American College of Medical Genetics profi- ciency testing program for laboratories performing cy- togenetic tests based on fluorescence in situ hybridiza- tion (FISH). Data Sources.—Eight proficiency surveys dealing with FISH detection of microdeletions or microduplications, an- euploidy in interphase cells, gene amplification, and neo- plasm-specific translocations. Participating laboratories used their own DNA probes (commercial or home-brew), hybridization methods, and analytic criteria to answer clin- ical questions about cases represented by slides included in the survey materials. They also described their test re- sults according to the International System for Human Cy- togenetic Nomenclature (ISCN) and answered supplemen- tary questions relating to their experience with the subject test systems. Data Extraction.—In addition to evaluating diagnostic accuracy, we evaluated survey use, laboratory experience, variation in methodologic approach, and the practicality of using ISCN nomenclature for describing test results. Synthesis and Conclusions.—With the exception of one challenge, at least 80% of the participants reached the cor- rect diagnostic conclusion. In the sole exception, there was still a consensus of 91.7% of participants with the same (albeit erroneous) diagnostic conclusion. The overall out- standing performance of participating laboratories clearly shows the reliability of current FISH methods. Despite the fact that a large number of laboratories reported little or no experience with the specific test systems, the over- whelming majority performed very well. This result shows that the program’s strategy of targeting classes of abnor- malities (vs a single abnormality associated with a specific disease) did not put at a disadvantage participants who did not routinely perform all of the potential tests in the class. The extraordinary variation in ISCN descriptions submitted by participants showed that the existing system for human cytogenetic nomenclature is not suitable for facile com- munication of FISH test results. (Arch Pathol Lab Med. 2002;126:1458–1462) F luorescence in situ hybridization (FISH) using chro- mosome-specific probes has become an important cy- togenetic tool in the evaluation of many congenital (con- Accepted for publication June 25, 2002. From the Genetic Services, Children’s Hospital, San Diego, Calif (Dr Mascarello); the Cytogenetics Laboratory, University of Utah Medical Center, Salt Lake City, Utah (Dr Brothman); the College of American Pathologists, Northfield, Ill (Ms Davison); the Division of Laboratory Genetics, Mayo Clinic, Rochester, Minn (Dr Dewald); the Department of Pathology, University of Pennsylvania School of Medicine,Philadel- phia, Pa (Dr Herrman); the Department of Medical & Molecular Ge- netics, Indiana University Medical Center, Indianapolis, Ind (Drs McCandless and Vance); the Department of Pathology, Dartmouth- Hitchcock Medical Center, Lebanon, NH (Dr Park); the Department of Pathology and Laboratory Medicine, University of Kansas Medical Cen- ter, Kansas City, Kan (Dr Persons); the Department of Pediatrics, Uni- versity of North Carolina, Chapel Hill, NC (Dr Rao); the Department of Pathology, University ofTexas Southwestern Medical Center, Dallas, Tex (Dr Schneider); and the Section of Medical Genetics and Molecular Medicine, Children’s Mercy Hospital, Kansas City, Mo (Dr Cooley). Each author is or was a member or consultant of the CAP-ACMG Cytogenetics Resource Committee. stitutional) disorders, hematologic malignancies, and some solid tumors. The Cytogenetics Resource Committee (CyRC) of the College of American Pathologists and the American College of Medical Genetics (CAP-ACMG) as- sessed the demand for proficiency testing and the feasi- bility of providing test materials in 3 pilot surveys that were offered in 1995 and 1996. 1 Based on the favorable response to these pilot surveys, the CyRC began offering regular proficiency surveys for chromosome-specific FISH in October 1997. To date, the CyRC has completed and evaluated 8 pro- ficiency surveys. The purpose of this report is to review laboratory performance, use, and limitations of the sur- veys offered in this program. MATERIALS AND METHODS Cells used in the CYF and CYG FISH surveys were obtained from blood, lymphoblastoid cell lines, and amniocyte cultures. Reprints: JamesT. Mascarello, PhD, Genetic Services, Children’s Hos- pital, 3020 Children’s Way, San Diego, CA 92123 (e-mail: jmascarello@ chsd.org).