By John Otrompke
CHICAGO -- November 5, 2009 -- In most cases, testing for myelodysplastic syndrome (MDS) by conventional cytogenetics is sufficient to identify cases of the disease, usually rendering testing by the more recent method of fluorescence in situ hybridisation (FISH) unnecessary, according to a study presented here at the American Society for Clinical Pathology (ASCP) 2009 Annual Meeting.
"We found that conventional cytogenetics are sufficient in the context of an adequate study, meaning that you have >=20 consecutive well-stained, well-spread metaphases," said Kaaren K. Reichard, MD, University of New Mexico, Albuquerque, New Mexico, at a presentation on November 2.
"Well spread means the chromosomes are dropped onto a slide, not all overlapping like a pile of spaghetti. They have to be sufficiently distinct to evaluate," she added.
In the study, the researchers examined 101 cases of MDS, a primary myeloid malignancy of the bone marrow that belongs to the group of diseases that includes acute leukaemia, and 35 control cases. Both groups were evaluated for 4 genetic variations commonly associated with MDS by FISH testing, a method of performing genetic testing that has been around since the 1990s, according to Dr. Reichard.
"In FISH testing, segments of DNA are tagged with fluorochrome, and when they stick to something inside the cell to which they are homologous or complementary, we can look at the cells and see if the piece of DNA is present, absent, or otherwise abnormal," she explained.
A discrepancy in the test result was found in 1 case; conventional cytogenetics found a normal result, but FISH testing revealed a difference in 1 gene in 20% of cells. The study also found a difference of 1 gene in 1 case.
"In that particular case, the patient not only had myelodysplastic syndrome but also a lymphoma," Dr. Reichard explained. "The patient actually had 2 diseases. Normally, cells do not spontaneously divide in the culture; the cells that do divide are precursor cells," she explained. "We think we picked up lymphoma cells when we did the FISH testing," she added.
The study concluded that conventional cytogenetic studies are usually sufficient to detect MDS and that FISH testing is unnecessary.
[Presentation title: Fluorescence in Situ Hybridization (FISH) Testing for -5/5q, -7/7q, +8, and del(20q) in Primary Myelodysplastic Syndrome (MDS) Is Unnecessary in the Setting of an Adequate Conventional Cytogenetic Study. Abstract 6]
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