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

Area of Science:

• Hematology
• Flow Cytometry
• Neoplastic Hematology

Background:

• Accurate blast quantification in bone marrow (BM) is essential for diagnosing myeloid neoplasms.
• Current cytomorphology analysis is the gold standard but can be labor-intensive.
• Flow cytometry offers a promising alternative for enumerating specific cell populations like CD34 myeloid cells (CD34M), but is affected by BM hemodilution.

Purpose of the Study:

• To validate the accuracy of a modified Holdrinet index (mHI) in correcting for BM hemodilution.
• To assess the reliability of mHI-adjusted flow cytometry for quantifying BM-exclusive cell subsets, such as CD34M.
• To determine if mHI-adjusted flow cytometry can serve as a practical alternative to traditional cytomorphology.

Main Methods:

• Analysis of two differently hemodiluted BM samples from 51 patients with suspected myelodysplasia.
• Application of the modified Holdrinet index (mHI) to assess BM white blood cell purity.
• Flow cytometry was used to enumerate CD34 myeloid cells (CD34M) and other BM-exclusive subsets.

Main Results:

• The study confirmed the accuracy of the modified Holdrinet index (mHI) in assessing BM white blood cell purity across varying hemodilution levels.
• mHI-adjusted flow cytometry counts for CD34 myeloid cells (CD34M) demonstrated reliability.
• The findings suggest that mHI-adjusted flow cytometry is independent of hemodilution effects.

Conclusions:

• The modified Holdrinet index (mHI) is an accurate tool for correcting bone marrow hemodilution in flow cytometry.
• mHI-adjusted flow cytometry provides a reliable and practical alternative to cytomorphology for blast quantification.
• This method offers a valuable approach for evaluating myeloid neoplasms, particularly CD34 myeloid cells, irrespective of sample hemodilution.