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Ensuring That Genetic Testing From Different Laboratories Yields the Same Results

10.07.2006

For individuals who develop colorectal cancers at a young age or have a family history of such cancers, microsatellite instability testing (MSI) has become an almost standard component of clinical evaluation. This DNA-based test can uncover hereditary nonpolyposis colon cancer syndrome (HNPCC), also called Lynch’s syndrome. However, despite the increased use of this test, there have been no reports of how well the results from any given laboratory agree with any other laboratory. In an article in the current issue of Cancer Biomarkers, researchers conducted testing across 6 laboratories to evaluate variability in reported results.

Because the underlying technology, PCR amplification, is now routine in all molecular genetics laboratories, there has been an implicit assumption that MSI testing would be reproducible and reliable. The initial results uncovered significant discordance among laboratories and led the researchers to expand their study in an attempt to learn the causes of the disagreements.

The six laboratories, located in the United States, Canada, and Australia, were members of the Cooperative Family Registry for Colon Cancer Studies (also called the Colon CFR). Using tumor samples collected since 1998 through the CFR, MSI testing was done at the six laboratories. Three of the laboratories had more than 8 years each of prior experience in MSI testing, while the other three set up MSI assays specifically for the Colon CFR. When the result showed wide disagreement with no systematic trends, one of the most experienced laboratories was designated the “gold standard” reference facility. With further testing of samples among the most experienced laboratories, the credentials of the reference laboratory were validated. A review of the results from all of the facilities resulted in five key rules that laboratories should observe when conducting MSI testing. Using these lessons learned, a final set of testing showed much improved agreement across all six laboratories.

Writing in the article, Noralane M. Lindor states, “This experience flushed out some important principles in MSI testing…and demonstrated that a very high degree of concordance for MSI testing is feasible….We strongly urge all clinical and research laboratories conducting MSI to participate in a sample exchange validation with an experienced group or consortium and that clinical laboratory certifying bodies develop plans to evaluate quality of MSI testing results being returned to clinicians and patients.”

The article is “Ascending the Learning Curve – MSI Testing Experience of a Six-Laboratory Consortium” by Noralane M. Lindor, Regenia Smalley, Melissa Barker, Jeannette Bigler, Lisa M. Krumroy, Annette Lum-Jones, Sarah J. Plummer, Teresa Selander, Sushma Thomas, Michelle Youash, Daniela Seminara, Graham Casey , Bharati Bapat, and Stephen N. Thibodeau. It appears in a special issue of Cancer Biomarkers, Volume 2, Issues 1-2 (July 2006), Lynch Syndrome (HNPCC) and Microsatellite Instability 2, published by IOS Press.

Lynch Syndrome (HNPCC) and Microsatellite Instability 2
Cancer Biomarkers, Volume 2, Issues 1-2 (July 2006)
Guest Editor: Asad Umar

Table of Contents

Asad Umar: Lynch Syndrome (HNPCC) and Microsatellite Instability Analysis Guidelines

Noralane M. Lindor et al.: Ascending the Learning Curve – MSI testing experience of a Six-Laboratory Consortium

Emanuela Lucci-Cordisco, Luigi Boccuto, Giovanni Neri, Maurizio Genuardi: The Use of Microsatellite Instability, Immunohistochemistry and Other Variables in Determining the Clinical Significance of MLH1 and MSH2 Unclassified Variants in Lynch Syndrome

Darryl Shibata: When Does MMR Loss Occur During HNPCC Progression?

Ivana Fridrichova: New Aspects in Molecular Diagnosis of Lynch Syndrome (HNPCC)

Won-Seok Jo and John M. Carethers: Chemotherapeutic Implications in Microsatellite Unstable Colorectal Cancer

John I. Risinger, et al.: Gene Expression Analysis of Tumor Infiltrating Lymphocyte Markers in Endometrial Cancers Indicates No Significant Increases in Those Cases with Microsatellite Instability

Stefan M. Woerner, et al.: Microsatellite Instability in the Development of DNA Mismatch Repair Deficient Tumors