I have stated quite a few times that a bone marrow biopsy does not determine adequate platelet production, regardless of what we are hearing from our doctors. I have not been able to find any publications that state this. I asked the PDSA if they knew who could answer the question, and it was passed on to 4 of the PDSA medical advisors. This is the answer that one of them gave, the other three fully agreed with the answer:
"I dont understand why anyone would use a bone marrow test to determine whether a patient is a candidate for Nplate or Promacta. My guess is that the doctor making this statement believes that if the bone marrow is normal (normal number of megakaryocytes) or is consistent with ITP (normal or increased number of megakaryocytes) that this shows that the bone marrow is making an adequate number of platelets and that production is therefore "normal" and that the patient is therefore not a candidate for a class of drugs that increase platelet production.
Nothing could be further from the truth. A bone marrow is a static sample and does not tell the doctor whether the normal or increased number of megakaryocytes is actually producing platelets. A large number of studies over the past 90 years have suggested that the normal or increased number of bone marrow megakaryocytes in the ITP patient bone marrow is not producing platelets adequately. Rather these megakaryocytes are probably being attacked by the immune system and undergoing programmed cell death (apoptosis) and die before they have a chance to make platelets.
The bone marrow test cannot be used to determine whether Nplate or Promacta will be effective.
With regard to when to do a bone marrow biopsy, the new (and the old) guidelines suggest that in adults it is rarely recommended except in those who have not responded to initial therapies, those over 60 (to exclude myelodysplastic syndromes) or those contemplating splenectomy. I rarely see a need to do a bone marrow biopsy in most of my patients except for those who fail to respond to initial therapy and those older patients who might have MDS (again reserving it mostly for those who do not have a robust response to initial therapy or those who might have other cytopenias). In a patient who has responded well to initial therapy and will then go on to splenectomy, I dont usually see a need for a bone marrow."
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