Melissa H. Cessna, MD
Ann Taylor, MD
Ancillary testing (PDF, 3.3 MB) plays an important role in bone marrow evaluation. However, it is often difficult to predict which testing will be indicated at the time of the bone marrow biopsy procedure. Our custom bone marrow requisition form (PDF, 3.3 MB) was developed to promote cost-effective use of ancillary testing—that is, testing other than microscopic evaluation of morphology. Previously, our clinicians compensated for the uncertainty by ordering every test that might be indicated based on their clinical differential diagnosis. While sometimes the testing did end up being relevant, we recognized, upon review of the morphology, that many of the tests did not end up being indicated or relevant to the diagnosis. We then opened a dialogue with our reference laboratory to explore other ways to order these tests such that they would not compromise the viability of the sample but would allow us to triage testing based on the morphology. We now offer triage of flow cytometry, chromosome analysis, FISH, and molecular studies. These options have been tailored to our clinical practice and may not be appropriate for every practice.
Flow cytometry. We offer the clinicians the options of ordering flow cytometry upfront or as “hold flow cytometry,” which allows the pathologist to triage the flow cytometry study based on morphology of the aspirate smears and touch imprints. We perform our own flow cytometry testing and can easily triage this testing because we review all of the bone marrows in our system.
Cytogenetic studies. With the help of our main reference laboratory, we are able to send samples for cytogenetics “process and hold.” The cytogenetics laboratory will process the sample and grow the cultures. If we do not add on chromosome analysis or FISH studies, the cytogenetics lab will pellet the culture and store it for 90 days. This gives us plenty of time to review the morphology and add on the testing if it appears indicated based on morphology. Additionally, if we decide not to add on these studies based on the morphology or because it is not clear that additional studies would alter clinical management, the clinician is given the option to request the testing up to 90 days later (after full review of the clinical case or discussion with the patient or both). Our understanding is that our reference laboratory is able to bill for this using existing CPT codes for cell culture. The cost for this processing is much less than that of full chromosome analysis. This test option is currently offered on our requisition form as “pathologist discretion” under chromosome analysis. We also work with a second reference laboratory for some of our work, and it, too, has agreed to offer this ordering option for us. It is willing to hold the cytogenetic sample for two weeks.
We offer several options for FISH studies, including “pathologist discretion,” routine (upfront), and reflex FISH. FISH studies can typically be added on (assuming sufficient sample) to an evaluation as long as a sample was sent to cytogenetics, either for chromosome analysis or process and hold. For reflex FISH, FISH is added on only if chromosome analysis is normal. The pathologist discretion option is helpful in limiting unnecessary testing if ordered for prognostic purposes for a suspected but not documented diagnosis (for example, multiple myeloma, CLL). Previously, our clinicians would order multiple myeloma FISH studies for every MGUS (monoclonal gammopathy of unknown significance) evaluation, the vast majority of which do not end up being multiple myeloma. We do recognize there is an advantage to having the plasma cells sorted prior to FISH for plasma cell myeloma, typically within the first 48 hours of collection. However, there are currently no CPT codes that cover the CD138 cell sort. Therefore, we work with our laboratory on a case-by-case basis to determine which cases should be sorted as part of the process and hold. The ability to triage FISH testing also allows us to add on indicated testing based on the morphologic diagnosis, which may not always be expected at the time of the bone marrow procedure.
Molecular studies. We offer DNA extraction and RNA extraction as a triage option for possible molecular studies. Molecular markers are playing an increasingly important role in diagnosis of hematologic disorders and management of acute leukemias. These markers define prognostic categories in acute leukemias, which can determine treatment course (e.g. consolidation versus bone marrow transplantation in first remission), and can also be used for minimal residual disease monitoring. However, the menu of recognized markers is ever increasing and it is not always clear which markers will be relevant for a particular leukemic case until the cytogenetic results are known. Our approach in general has been to wait for results of chromosome analysis and any relevant FISH studies before proceeding with molecular testing. That way, we have a better idea which molecular tests will be necessary for clinical management based on algorithms established in our institution. For example, if chromosome analysis of a new acute myeloid leukemia shows an inversion 16, than we can go back to the extracted DNA held in reserve and test for KIT for prognosis and to the RNA to test for the fusion transcript CBFB-MYH11 to verify amplifiability for monitoring. But if chromosome analysis shows a complicated karyotype that stratifies the patient as high risk, molecular testing would not alter prognosis.
Our main reference laboratory has agreed to store the extracted DNA and RNA indefinitely (at least for now, this may change with storage requirements). Our other reference laboratory will store these samples for three weeks, which is typically sufficient time to determine which molecular studies are indicated. An advantage to the long-term storage provided by our main reference laboratory is that the diagnostic sample is always available to confirm the validity of a test for monitoring, particularly as new tests become available.
We began offering these triage options about two years ago. Since implementing these options, we have seen a significant shift in ordering patterns. The standard order set previously included flow cytometry and cytogenetic studies with or without FISH. Most bone marrow evaluations for primary diagnosis now come with pathologist-discretion orders for cytogenetic studies, and hold flow is ordered more frequently than before. Other pathologists in our system have started to offer these triage options and they, too, are starting to see this trend. Using this framework and with input from our oncologists and reference laboratory, we have also been able to develop a cost-effective algorithmic approach to acute leukemia diagnosis and followup. This has been successful because of our close working relationship with our reference laboratories and because we maintain open communication with our clinicians about these cases. The clinicians see the value in our triaging these cases and trust that we will order the appropriate testing and/or give them the option to order additional tests that may be needed for their evaluation.
Drs. Cessna and Taylor are co-directors of hematopathology for the Urban Central Region of Intermountain Healthcare, Salt Lake City. Their approach to triage of ancillary testing in bone marrow evaluation was profiled as part of the CAP’s transformation plenary at the CAP ’10 annual meeting. Their article here is their response to questions raised after the presentation.