Peripheral Blood Analysis-Special Technique High Resolution Banding

BACKGROUND:

HIGH RESOLUTION BANDING
High resolution banding has the advantage of  obtaining elongated chromosomes, so that finer details and a larger number of bands can be visualized.

INDICATIONS FOR TESTING:

HIGH RESOLUTION BANDING                                                                                                             High resolution banding studies are performed on patients suspected of having a nonspecific chromosome abnormality. Initial routine karyotype should be normal, and FISH studies for specific microdeletion syndromes negative.

SAMPLE REQUIREMENTS:

Five milliliters of whole blood collected by venipuncture into a green top sodium heparin tube.

SPECIMEN HANDLING:

Blood may be stored at room temperature overnight, refrigerated up to three days, but never frozen. Blood may also be mailed by overnight courier at ambient temperature. Blood drawn more that five days prior to receipt, or in the wrong tube (such as lithium heparin), is unacceptable.

PROCEDURE:

HIGH RESOLUTION BANDING
Cells cultured under the same conditions as routine bloods are synchronized at the pre-mitosis (S/G1) interphase by using methotrexate, and released from their block by adding a pulse of thymidine. Cells are cultured total of 96 (instead of 72) hours.

INTERPRETATION:

HIGH RESOLUTION BANDING
High resolution banding studies detect the same abnormalities as regular banding studies. However, additional subtle abnormalities such as small duplications, deletions, insertions and inversions of the chromosomes may be resolved at this level.

RESULTS:

Results are presented according to the international standards for chromosomal nomenclature (ISCN 2005), and a full explanation of the karyotype and clinical implications is provided. Any abnormal or variant results are followed by genetic counseling.

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