Chromosome Analysis, Hematologic Disorders, Blood
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Chromosomal abnormalities play a central role in the pathogenesis, diagnosis, and monitoring of treatment of many hematologic disorders. Whenever possible, it is best to do chromosome studies for neoplastic hematologic disorders on bone marrow. Bone marrow studies are more sensitive and the chances of finding metaphases are about 95%, compared with only a 60% chance for blood studies. When it is not possible to collect bone marrow, chromosome studies on blood may be useful.
When blood cells are cultured in a medium without mitogens, the observation of any chromosomally abnormal clone may be consistent with a neoplastic process.
See An Expanded Algorithm for the Laboratory Evaluation of Suspected Multiple Myeloma in Special Instructions. Also see Diagnosis and Monitoring of Multiple Myeloma in Publications.
Assisting in the classification and follow-up of certain malignant hematological disorders when bone marrow is not available
The presence of an abnormal clone usually indicates a malignant neoplastic process.
The absence of an apparent abnormal clone in blood may result from a lack of circulating abnormal cells and not from an absence of disease.
On rare occasions, the presence of an abnormality may be associated with a congenital abnormality and, thus, not related to a malignant process. When this situation is suspected, follow-up with a medical genetics consultation is recommended.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
We recommend consultation with personnel from the Cytogenetics Laboratory when considering blood studies for hematologic disorders.
Bone marrow specimens are preferred over peripheral blood specimens for the diagnosis of neoplastic hematologic disorders. When peripheral blood must be used, FISH studies may detect some disorders better than conventional chromosome studies.
FISH studies will detect chromosome anomalies with prognostic significance much more often than conventional chromosome studies for:
-Chronic lymphocytic leukemia (CLL).
-Plasma cell proliferative disorders (PCPDs) such as multiple myeloma.
-FISH studies also may be superior for other hematological disorders when compared to conventional chromosome studies utilizing blood specimens.
This test is not useful for the following reasons/disorders: multiple miscarriages, infertility, pregnancy loss, multiple congenital anomalies, developmental delay, Down syndrome, Turner syndrome, premature ovarian failure, amenorrhea, ambiguous genitalia, and other congenital abnormalities. The appropriate test for these situations is CMS/8696 Chromosome Analysis, for Congenital Disorders, Blood.
-Cell lysis caused by forcing blood quickly through the needle at collection
-Use of an improper anticoagulant (sodium heparin is best) or improperly mixing the blood with the anticoagulant
-Excessive transport time
-Exposure of the specimen to temperature
-Abnormalities missed due to sampling error
-Subtle structural chromosome abnormalities may be missed occasionally
-Neoplastic cells not dividing or not circulating in the bloodstream
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
46,XX or 46,XY. No apparent chromosome abnormality.
An interpretative report will be provided.
Clinical References Provides recommendations for further in-depth reading of a clinical nature
Dewald GW, Ketterling RP, Wyatt WA, Stupca PJ: Cytogenetic studies in neoplastic hematologic disorders. In Clinical Laboratory Medicine, 2nd edition. Edited by KD McClatchey. Baltimore, Williams & Wilkens, 2002, pp 658-685