John A. Widness, MD
Peer Review Status: Internally Peer Reviewed

Chromosome Analysis

To obviate the need for doing an unnecessary bone marrow analysis, it is essential to check that a prenatal chromosome analysis via CVS, amniocentesis, or cordocentesis has not previously been done. Infants with multiple anomalies may have been previously evaluated by Ob-Gyn and thus tested.

Situations in which procedure may be considered:

Although a diagnosis can be made in a relatively short time (6-30 hours vs. 48-96 hours for peripheral blood samples), the use of bone marrow aspirations should be reserved for the diagnosis of conditions which are considered to be incompatible with life such as Trisomy 13, 18, or Triploidy (rarely). Accordingly, a patient with probable Down Syndrome would normally not be a candidate. In considering bone marrow aspiration, the technical of doing so must be considered. These include:

  1. The failure rate for chromosome results for bone marrow sample is high (8-10%) relative to that of peripheral blood (<1%)
  2. Chromosome morphology is generally poor, not allowing for identification of small, chromosomal rearrangements
  3. Even in successful cases, the yield of analyzable cells is small increasing the risk of missing mosaicism.

While the results are pending, most situations are ones in which non-surgical life support therapies should be offered after discussion with the medical staff and the family.

Who to contact:

Weekdays before 3 pm: Prior to bone marrow aspiration, contact the Cytogenetics Laboratory staff must be called (6-3877) so that the necessary preparation for processing a specimen can be made. If possible, schedule the aspiration prior to 3 pm on weekdays since specimen processing takes approximately 2 hours.

To obtain a bone marrow specimen, the pediatric hematologist may be consulted (beeper 339-9023) and the Bone Marrow Laboratory notified (6-2543) if a smear of the marrow is desired. Since it is the nursery's responsibility to provide the necessary equipment, Central Sterilizing Service must be contacted to provide a "bone marrow aspirate set-up tray". Delivery takes appropriately one half hour.

Evenings or weekends: Prior to bone marrow aspiration contact the staff geneticist on call (131-1681), and the cytogenetics lab person on call (call the Cytogenetics Lab at 6-3877 for the recorded message of the current beeper number, or call the long-distance beeper: 1-800-202-8098). Do not perform the bone marrow aspiration until someone from the Cytogenetics Laboratory has been contacted since results cannot be obtained from the specimen if the sample is not processed within 1-2 hours.

Procedure:

Obtain 1-3 cc of bone marrow sample in a green-top heparinized tube. Also obtain a blood sample (2-3 cc) in a green-top tube for a chromosome analysis in case the marrow specimen fails to yield adequate results. If there is enough volume from a marrow sample, the specimen can be set up for both 2 and 24 hour processing. In small aspirate samples, only the 24 hour culture will be set up. Preliminary results from banded chromosomes will be available within six to thirty hours. The final report will be provided in 5-10 days.

Thrombocytopenia

Bone marrow aspiration for neonatal thrombocytopenia (platelet count < 50,000/mm3) is usually not necessary. However, in difficult or persistent cases, it may be helpful to discuss the evaluation and treatment of this condition with a member of the pediatric hematology division.

References

  1. Christensen R D, Rothstein G, Anstall H B, Bybee B Granulocyte transfusions in neonates with bacterial infection, neutropenia, and depletion of mature marrow neutrophils. Pediatrics, 1982;70:1-6.
  2. Cordle D G, Strauss R G (1993). Guidelines for Neonatal Transfusion Therapy - 1993. Iowa City:UIHC Elmer L. DeGowin Memorial Blood Center, University of Iowa Hospitals and Clinics, 1993. (reprinted in this book, pp. __ - ___).
  3. Strauss R G. Current status of granulocyte transfusions to treat neonatal sepsis. J Clin Apheresis 1989;5:25-29.