Peripheral Blood: 88230-52, 88271, 88273, 88291
Amniotic Fluid: 88235-52, 88271, 88273, 88291
|Specimen Requirements||Peripheral Blood||Amniotic Fluid|
|Container||Sodium Heparin (green top tube)||Two 15 ml sterile leak-proof conical tubes|
|Optimal Quantity||2-3 ml||20-25 ml|
|Minimum Quantity||1-2 ml||10 ml|
|Storage||Room Temperature||Room Temperature|
|Stability at Room Temperature||Room Temperature for 8 hours, then refrigerate||Room Temperature for 8 hours, then refrigerate|
|Transportation||Avoid freezing or heating over 35oC||Avoid freezing or heating over 35oC|
Peripheral Blood: Final report in 5 days for 90% of cases
Amniotic Fluid: Final report in 7-10 days for 90% of cases
Fluorescence in situ hybridization (FISH) is a sensitive method to detect smaller genomic changes associated with various micordeletion syndromes. There are several advantages with FISH technology over routine chromosome analysis and such advantages include the ability of FISH technology to detect genomic abnormalities in non-viable and non-dividing tissues, rapid turnaround time, and increased resolution. However, FISH technology is complementary to routine chromosome analysis and cannot substitute routine chromosome analysis and FISH diagnostic testing is not recommended as an isolated test without chromosome analysis for the diagnosis of these microdeletion syndromes.
Prader-Willi syndrome, caused by microdeletions/loss of paternally derived gene expression, is a panethnic developmental disorder affecting approximately 1 in 10,000 to 1 in 15,000 live births. Patients with this syndrome show characteristic features including unusual facial appearance, short stature, severe mental retardation, spasticity and seizures. Chromosome deletion 15q11q13 during male meiosis results in Prader-Willi syndrome and such deletions account for a large number of patients while a small number of patients have mutations within this gene that cannot be detected by either routine chromosome analysis or FISH. Since the most common deletion encompasses ~3 Mb, often these deletions are not detected on routine chromosome analysis. FISH is the ideal choice for detection of this deletion due to its increased sensitivity.
The sample is usually cultured until sufficient number of mitotic cells is observed (48-72 hours for peripheral blood and 7-10 days for amniotic fluid) and after harvesting the cells are hybridized with the probes. After hybridization and post-hybridization washes, the slides are analyzed under a fluorescence microscope equipped with epifluorescence and appropriate filter sets. Analysis and scoring is carried out by two certified technologists in a blinded fashion with each scoring a minimum of 5 metaphases and 50 interphase nuclei. Results are reviewed by both the laboratory manager and the director.
15q11 deletion (Prader-Willi syndrome) SNRPN / 154P1 Cytocell (cat # LPU005)
Interpretation of Results
The morphologic interpretation and correlation of results on all cases is performed by a board-certified doctoral level scientist (laboratory director). The final report has a narrative description of results. If abnormalities are present, they are explained in a paragraph which helps to clarify and correlate chromosomal findings with phenotype. References are included in the report to help the referring physician with interpretation, which include books or journals that contain appropriate information. Recommendations are made as to any additional testing, if necessary.