Focus on the Holdrinet index: Toward blast quantification by flow cytometry

Blast quantification in the bone marrow (BM) is crucial for evaluating myeloid neoplasms, with cytomorphology being the only recognized analysis. The CD34 myeloid cell (CD34M) count by flow cytometry is promising but impaired by BM hemodilution. A modified version of the Holdrinet index (mHI) is routinely used to assess it, though not yet validated. By analyzing two differently hemodiluted BM samples from 51 patients with suspicion of myelodysplasia, this study confirms mHI accuracy in assessing BM white blood cell purity. mHI-adjusted count by flow cytometry of BM-exclusive cell subsets, such as CD34 myeloid cells, may offer a reliable and practical alternative to cytomorphology analysis, independently from hemodilution.