Section E9 of the American College of Medical Genetics technical standards and guidelines: fluorescence in situ hybridization.

This updated Section E9 has been incorporated into and supersedes the previous Section E9 in Section E: Clinical Cytogenetics of the 2008 Edition (Revised 02/2007) American College of Medical Genetics Standards and Guidelines for Clinical Genetics Laboratories. This section deals specifically with the standards and guidelines applicable to fluorescence in situ hybridization analysis.

Section E6.5 of the ACMG technical standards and guidelines: chromosome studies for solid tumor abnormalities.

PURPOSE: : Cytogenetic analysis of tumor tissue detects clonal abnormalities. The information obtained from these studies is utilized for diagnosis, prognosis, and patient management. METHODS: : The Working Group of the Laboratory Quality Assurance Committee of the American College of Medical Genetics provides these Standards and Guidelines for chromosome studies for solid tumors abnormalities as a resource for clinical cytogenetic laboratories. RESULTS: : The guidelines incorporate aspects of sample procurement, handling, processing, harvesting, analysis, quality control, and quality assurance. It is recommended that all pediatric solid tumors be studied by cytogenetic analysis when feasible due to the clinical and therapeutic implications of the genetic abnormalities. Cytogenetic analysis of certain adult solid tumors also provides information that impacts diagnosis and therapeutics. Molecular cytogenetic analysis or fluorescence in situ hybridization (FISH) may be a primary or secondary method of evaluation of the tumor tissue. FISH can document a specific molecular event, e.g. gene rearrangement, provide a rapid result to aid in the differential diagnosis or planning of therapy, clarify chromosome anomalies, or assess gene amplification. CONCLUSION: : Genetic analysis adds valuable information to the understanding of and therapeutic approach to solid tumors. Laboratories may use their professional judgment to make modifications or additions to these guidelines.

Proficiency testing for laboratories performing fluorescence in situ hybridization with chromosome-specific DNA probes.

OBJECTIVE: To assess laboratory performance, use, and limitations in the joint College of American Pathologists and American College of Medical Genetics proficiency testing program for laboratories performing cytogenetic tests based on fluorescence in situ hybridization (FISH). DATA SOURCES: Eight proficiency surveys dealing with FISH detection of microdeletions or microduplications, aneuploidy in interphase cells, gene amplification, and neoplasm-specific translocations. Participating laboratories used their own DNA probes (commercial or home-brew), hybridization methods, and analytic criteria to answer clinical questions about cases represented by slides included in the survey materials. They also described their test results according to the International System for Human Cytogenetic Nomenclature (ISCN) and answered supplementary 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 correct 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 outstanding 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 overwhelming majority performed very well. This result shows that the program's strategy of targeting classes of abnormalities (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 communication of FISH test results.

HER-2 fluorescence in situ hybridization: results from the survey program of the College of American Pathologists.

CONTEXT: Fluorescence in situ hybridization (FISH) is a common method used to determine HER-2 status in breast cancer. Limited information is available concerning reproducibility of FISH in determining HER-2 gene amplification. OBJECTIVE: To present proficiency testing results of FISH for HER-2 conducted by the Cytogenetics Resource Committee of the College of American Pathologists/American College of Medical Genetics. DESIGN: During the past 5 years, unstained sections from 9 invasive breast carcinomas were used for HER-2 FISH proficiency testing, allowing for comparison of FISH results among a large number of laboratories. Additional data were collected using an educational (ungraded) challenge and supplemental questions in the surveys. RESULTS: The number of laboratories participating in HER-2 FISH proficiency testing has increased steadily during the past 5 years (from 35 in 2000 to 139 in 2004). Reproducibility of test results among laboratories was excellent for breast tumors with low copy number (no HER-2 amplification) and for breast tumors with high copy number (HER-2 amplification). However, there was considerable variation in interpretation of results for a tumor with low-level HER-2 amplification that was tested on 2 separate occasions. Responses to supplemental questions indicated that there was a need for consensus on the use of a separate equivocal/borderline interpretative category and the need for standardization of cutoff values used to define interpretative categories. CONCLUSIONS: The College of American Pathologists proficiency survey programs provide useful information concerning the reproducibility of clinical testing for HER-2 by FISH and reflect clinical interpretation of HER-2 FISH analyses from laboratories across the country.

Cytogenetic heteromorphisms: survey results and reporting practices of giemsa-band regions that we have pondered for years.

CONTEXT: Cytogenetic heteromorphisms (normal variants) pose diagnostic dilemmas. Common Giemsa-band heteromorphisms are not described in the literature, although Giemsa-banding is the method most frequently used in cytogenetic laboratories. OBJECTIVE: To summarize the responses from more than 200 cytogeneticists concerning the definition and reporting of cytogenetic heteromorphisms, to offer these responses as a reference for use in clinical interpretations, and to provide guidance for interpretation of newly defined molecular cytogenetic heteromorphisms. DESIGN: The Cytogenetics Resource Committee of the College of American Pathologists and the American College of Medical Genetics administered a proficiency testing survey in 1997 to 226 participant cytogenetic laboratories. Supplemental questions asked whether participants considered particular Giemsa-banded chromosomal features to be heteromorphisms and if these would be described in a cytogenetic clinical report. RESULTS: Responses were obtained from 99% of participants; 61% stated they would include selected heteromorphism data in a clinical report. More than 90% considered prominent short arms, large or double satellites, or increased stalk length on acrocentric chromosomes to be heteromorphisms; 24% to 36% stated that they would include these in a clinical report. Heterochromatic regions on chromosomes 1, 9, 16, and Y were considered heteromorphisms by 97% of participants, and 24% indicated they would report these findings. Pericentric inversions of chromosomes 1, 2, 3, 5, 9, 10, 16, and Y were considered heteromorphisms with more than 75% of respondents indicating they would report these findings. CONCLUSIONS: Responses were not unanimous, but a clear consensus is presented describing which Giemsa-band regions were considered heteromorphisms and which would be reported.

Problems with ISCN FISH Nomenclature make it not practical for use in clinical test reports or cytogenetic databases [corrected].

PURPOSE: To assess the extent and the sources of variation in ISCN nomenclature used by participants in CAP/ACMG surveys dealing with fluorescence in situ hybridization (FISH). METHODS: Over 1600 nomenclature strings from 15 challenges in seven surveys were evaluated for the contributions of diagnostic errors, syntax errors, methodological differences, and technical factors not foreseen by ISCN 1995. RESULTS: Although diagnostic errors were uncommon, syntax errors were numerous, approaching 50% of the responses for several challenges. Their frequency varied with the complexity of the nomenclature required to describe a test condition. Variation attributable to probe selection and band designation correlated with the number of probes available for addressing the diagnostic issue at hand. In the most dramatic example of this effect, a survey simulating diagnosis of trisomy 21 in uncultured amniocytes, there were 66 participants (of 99) who used the same general form for their nomenclature, but only 8 of the 66 had exactly the same nomenclature string. Participants used proprietary names, created their own nomenclature, or ignored the true complexity of probe systems when trying to describe conditions not foreseen by ISCN 1995. CONCLUSION: The use of current ISCN FISH nomenclature resulted in survey participants describing unique biological conditions in a multitude of different ways. In addition to making the nomenclature unsuitable for proficiency test purposes, this heterogeneity makes it impractical for clinical test reporting and for cytogenetic database management. Because methodological information contributes a large amount of variability, adds complexity, and increases opportunities for syntax errors, a system that excludes such information would be more effective.