The challenging task of enumerating blasts in the bone marrow.

Area of Science:

• Hematology
• Oncology
• Diagnostic Pathology

Background:

• Accurate enumeration of bone marrow blasts is crucial for diagnosing and monitoring myelodysplastic syndromes, myeloproliferative neoplasms, and acute leukemias.
• Current standard microscopic counting methods lack sufficient examination regarding their accuracy and precision.

Purpose of the Study:

• To evaluate the accuracy and reproducibility of bone marrow blast counting using conventional microscopic techniques (aspirate smears and CD34-stained trephine biopsies).
• To compare these methods against a digital reference standard and flow cytometry.

Main Methods:

• Four experienced hematopathologists performed blast counts on aspirate smears and CD34-stained trephine biopsies.
• A "Digital Reference" was established using manual counts of individual cells on high-resolution digital images of CD34-stained biopsies.
• Flow cytometry was also used for blast enumeration.

Main Results:

• Hematopathologists' counts showed excellent interobserver reproducibility but poor correlation between smear and biopsy methods.
• Both smear and biopsy evaluations exhibited positive bias and high variability compared to the Digital Reference.
• Trephine biopsy counts had less variability but higher positive bias than smear counts, indicating overestimation.
• Flow cytometry counts correlated well with the Digital Reference.

Conclusions:

• Standard microscopic methods for bone marrow blast enumeration are prone to significant bias and variability.
• Improved counting methodologies, potentially involving digital imaging or alternative quantification strategies (e.g., per marrow area), are needed for critical clinical decisions.
• Further research into better blast cell markers and automated enumeration technologies is warranted.