Suspected blasts on peripheral blood smear
Author:
Mikael Häggström [note 1]
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When a tech or equivalent lets you know that there are suspected blasts on a peripheral blood smear, the following needs to be determined:
- If it is a new finding or a known condition in the patient, generally by a medical records lookup.
- Whether the cells are definite blast cells, suspected blast cells, or another cell type.
- The percentage of blasts compared to all white blood cells.
New finding of blast cells
If it is a new finding (not already being part of a known diagnosis), generally proceed as follows:
- During regular work hours, confirm that the person who reports on peripheral blood smears is notified about the case, so that the case is prioritized. Generally, the procedure is to make a complete peripheral blood smear report, in addition to calling the clinician about the presence of blasts. Further information: Peripheral blood smear
- During on call hours, ask the technician to perform a manual count if not already done.
- If you are close to the lab, generally look at the slide yourself as well to estimate the blast percentage.
- If you are far from the lab, ask a technician if images can be sent to you by micrography and telepathology.
Suspect or exclude acute promyelocytic leukemia (APL)
APL typically shows blast cells (high nuclear/cytoplasmic ratio, finely dispersed chromatin and prominent nucleoli) and Auer rods (as seen in top image). However, it may also have a hypogranular variant with very scant Auer rods.
Even a suspicion of APL on microscopy should be reported relatively quickly to the ordering clinician, without waiting for additional workup or for the regular work hours of people with more expertise.[note 2] Also report any suspicion of APL to the oncologist/hematologist on call if applicable.
Non-APL
Consult with a senior or hematopathologist as needed, before conveying a preliminary report to the lab technician and/or clinician. At least during on call hours, it is not necessary to speculate about further sub-classification of blast cells.
Notes
- ↑ For a full list of contributors, see article history. Creators of images are attributed at the image description pages, seen by clicking on the images. See Patholines:Authorship for details.
- ↑ The reason for the quick reporting of suspected APL is that even a suspected APL mandates immediate initiation of ATRA treatment before confirming or disproving the diagnosis by further workup, so initially, it is much better to report that you suspect it even if further workup will disprove that diagnosis, rather than delaying reporting and thereby the initiation of treatment for a patient that actually has APL. After all, the initial treatment only costs about $40 as a first dose.
- Indication for treatment: Sanz MA, Fenaux P, Tallman MS, Estey EH, Löwenberg B, Naoe T (2019). "Management of acute promyelocytic leukemia: updated recommendations from an expert panel of the European LeukemiaNet. ". Blood 133 (15): 1630-1643. doi:. PMID 30803991. PMC: 6509567. Archived from the original. .
- Cost of treatment: Dosage of ATRA in APL is 45 mg/m2/day administered as two evenly divided doses, which for a typical adult is about 40 mg as a first dose. The cost per 10mg capsule is about $10.
- Dosage reference: Osman AEG, Anderson J, Churpek JE, Christ TN, Curran E, Godley LA (2018). "Treatment of Acute Promyelocytic Leukemia in Adults. ". J Oncol Pract 14 (11): 649-657. doi:. PMID 30423270. Archived from the original. .
- Cost per 10mg capsule: . Vesanoid Prices. pharmacychecker.com. Retrieved on 2022-11-09.
The treatment must be started immediately to counteract severe coagulopathy of untreated APL.
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