# Contribution of XN‐10 Sysmex Parameters in the Cytological Monitoring of Acute Promyelocytic Leukemia

## TL;DR

This study explores how Sysmex haematology data can help monitor acute promyelocytic leukemia by improving cell count consistency and detection of blast cells.

## Contribution

A novel algorithm using Sysmex parameters is proposed to harmonize cytological monitoring of APL patients.

## Key findings

- An algorithm based on seven leukocyte subpopulation parameters predicted blast cell presence with 84.6% sensitivity and 86.7% specificity.
- The algorithm was validated on a separate cohort, showing potential for harmonizing cytological practices across different sites.

## Abstract

The all‐trans‐retinoic acid (ATRA) treatment used in acute promyelocytic leukemia (APL) has the particularity of inducing differentiation of the leukemia cells. As a result, within the same smear, several stages of cellular differentiation of the granular lineage are present, which can make it difficult to distinguish elements when counting cells.

The aim of this study is to use the technical data from Sysmex haematology equipment in patients with APL to improve their cytological monitoring and harmonize blood count results from one operator to another. We collected 132 samples from patients with APL over a period of 45 days from the day of diagnosis and divided them into two groups: presence or absence of blast cells on the blood smear.

Seven parameters of leukocyte subpopulations were selected for cytological monitoring. We developed a decision algorithm based on these, including decision thresholds for predicting the presence or absence of blasts. These data were verified on a validation cohort of 110 samples with APL, set up at a different site from the training cohort. The algorithm predicted the presence of blast cells in these samples with a sensitivity of 84.6% and a specificity of 86.7%.

In the context of cytological monitoring of patients with APL, the study of technical data has not been developed yet, despite the fact that this is a difficult and sometimes nonhomogeneous task from one operator to another. The proposed algorithm could be a facilitating tool in cytology to harmonize practices both within and between sites.