Prenatal Aneuploidy Detection, FISH
Method Description Describes how the test is performed and provides a method-specific reference
The FISH test is based on commercially available, directly-labeled, multicolored fluorescent DNA probes that are centromere-specific for chromosome 18, X, and Y, and locus-specific for 13q14 and 21q22.13-q22.2. These 5 probes are used for detection of aneuploidy for 13, 18, 21, X, or Y from 2.0 mL to 4.0 mL of uncultured amniotic fluid cells or from 1.0 mg to 3.0 mg of chorionic villi. A total of 200 cells are analyzed by 2 technologists for each probe. This FISH test can be performed on any tissue, but uncultured amniotic fluid cells or chorionic villi are preferred. Specimens with 2 signals for probes on chromosomes 13, 18, and 21, and either 1 X and 1 Y signal (male) or 2 X signals (female) are considered normal. Specimens with signal patterns other than 2 signals for 13, 18, and 21, and XX or XY are consistent with loss or gain of the locus in question. (Jalal SM, Law ME, Carlson RO, et al: Prenatal detection of aneuploidy by direct labeled multicolored probes and interphase fluorescence in situ hybridization. Mayo Clin Proc 1998;73:132-137)
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.
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location The location of the laboratory that performs the test