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Cytogenetic Studies: The Importance of Clinical Information

Accurate clinical information and differential diagnosis is critical for appropriate set up and interpretation of cytogenetic studies. Cell culture medium and choice of mitogenic stimulant is dependent on the diagnosis and type of cell to be analyzed. For constitutional abnormalities, phytohemagglutinin is used to stimulate growth of T lymphocytes. For neoplasms, different mitogens are used, such as pokeweed mitogen and lipopolysaccharide for neoplastic B lymphocytes in B-cell CLL/SLL and IL-4 for neoplastic plasma cells in plasma cell myeloma. The banding resolution and number of cells karyotyped are also based on clinical information. High-resolution banding is used for microdeletion syndromes and 50 cells are analyzed (instead of the usual 20) for suspected Turner syndrome. Fluorescence in-situ hybridization (FISH) probes are used when a specific chromosomal abnormality is suggested by the diagnosis. FISH is the test of choice for chimerism studies following hematopoietic stem cell transplantation when the donor is of the opposite sex. A panel of FISH probes is used in some neoplasms to provide prognostic information.

For constitutional chromosomal studies, essential clinical information includes:

  • Specimen source
  • Suspected clinical diagnosis or syndrome (if not known, specify dysmorphic features and other findings that suggest a constitutional abnormality)

For neoplastic studies, essential clinical information includes:

  1. Specimen source
  2. Suspected or known diagnosis (The most specific diagnosis should be provided, for example ‘mantle cell lymphoma’ instead of ‘non-Hodgkin lymphoma’, ‘suspected myelodysplasia’ instead of ‘anemia’)
  3. Suspected or known cytogenetic abnormality
  4. Disease status (active, remission, relapse)
  5. Hematopoietic stem cell transplantation status and donor sex

Admitting diagnoses and ICD-9 codes are almost never adequate for this purpose and, in fact, often provide misleading information. For example, a recent requisition form had the code 238.7, which includes myelodysplastic syndromes as well as several chronic myeloproliferative disorders, with different cytogenetic correlates. In another instance, a patient’s known history of Down syndrome was not provided. This resulted in the initial misinterpretation of bone marrow cytogenetic results as being consistent with a myeloid neoplasm, since trisomy 21 can be seen as an acquired abnormality in myeloid neoplasms.

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