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Test Catalog

Test ID: FXIST    
X-Inactivation (XIST), Xq13.2 Deletion, FISH

Method Description Describes how the test is performed and provides a method-specific reference

The identification of XIST deletions is based on FISH analysis of critical region loci (XIST) on the long arm of the X chromosome (Xq13.2). Metaphase cells are examined for the presence of the critical region loci at Xq13.2 (orange signal) and the control probe at the X centromere (green signal). Metaphase cells with normal X chromosomes will exhibit signals for both the critical region and control probe. Abnormal cells, those with an X-derived marker chromosome that is missing XIST, will exhibit only a control probe signal on the marker chromosome.(Crifasi PA, Michels VV, Driscoll DJ, et al: DNA fluorescent probes for diagnosis of velocardiofacial and related syndromes. Mayo Clin Proc 1995;195[70]:1148-1153)

PDF Report Indicates whether the report includes an additional document with charts, images or other enriched information


Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.

Samples processed Monday through Sunday. Results reported Monday through Friday, 8 a.m.-5 p.m. CST.

Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.

7 days

Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result

10 days

Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

Amniotic Fluid: Any remaining supernatant or whole fluid aliquots are discarded 14 days after results are reported.; Chorionic Villi: Discarded at the time results are reported.; Blood: 3 weeks; Skin Biopsy: Discarded at time results are reported

Performing Laboratory Location The location of the laboratory that performs the test