Consensus characterization of 16 FMR1 reference materials: a consortium study.

Fragile X syndrome, which is caused by expansion of a (CGG)(n) repeat in the FMR1 gene, occurs in approximately 1:3500 males and causes mental retardation/behavioral problems. Smaller (CGG)(n) repeat expansions in FMR1, premutations, are associated with premature ovarian failure and fragile X-associated tremor/ataxia syndrome. An FMR1-sizing assay is technically challenging because of high GC content of the (CGG)(n) repeat, the size limitations of conventional PCR, and a lack of reference materials available for test development/validation and routine quality control. The Centers for Disease Control and Prevention and the Association for Molecular Pathology, together with the genetic testing community, have addressed the need for characterized fragile X mutation reference materials by developing characterized DNA samples from 16 cell lines with repeat lengths representing important phenotypic classes and diagnostic cutoffs. The alleles in these materials were characterized by consensus analysis in nine clinical laboratories. The information generated from this study is available on the Centers for Disease Control and Prevention and Coriell Cell Repositories websites. DNA purified from these cell lines is available to the genetics community through the Coriell Cell Repositories. The public availability of these reference materials should help support accurate clinical fragile X syndrome testing.

Detection of immunoglobulin heavy chain gene rearrangements in classic hodgkin lymphoma using commercially available BIOMED-2 primers.

CONTEXT: Classic Hodgkin lymphoma (cHL) is regarded as a clonal B-cell neoplasm. The BIOMED-2 group recently validated a set of immunoglobulin heavy chain (IGH) multiplex primers with high sensitivity in B-cell non-Hodgkin lymphomas. We postulated that after using these primers, a higher proportion of the cHLs would have detectable rearrangements without microdissection. DESIGN: Forty-two patients with cHL were selected. The densities of Reed-Sternberg cells/10 high-power field and CD30+ cells/10 high-power field were classified as low, intermediate, or high. The quantities of background CD20+ B cells were classified as low or high. DNA from formalin-fixed, paraffin-embedded sections was used to perform polymerase chain reactions with the InVivoScribe IGH Gene Clonality Assay for ABI detection. Dominant peaks were considered to be monoclonal if they were >3x the height of the polyclonal background, and borderline monoclonal if between 2 and 3x. RESULT: Overall, 10/42 (24%) of the cHL samples were monoclonal, and 7/42 (17%) were borderline monoclonal. Higher densities of CD30+ cells and lower background B cells were statistically correlated with clonality. CONCLUSIONS: The BIOMED-2 primers demonstrate IGH gene clonality in 24% to 40% of cHLs without microdissection. In a subset of the cHL, the IGH gene rearrangement analysis might be useful for diagnosis, but can lead to confusion between cHLs and non-Hodgkin lymphomas if used as a discriminative criterion.