Study Assesses Differences Between WHO, ICC Criteria on MDS

A new study suggests there are “few but important differences” between the International Consensus Classification (ICC) and updated World Health Organization (WHO) diagnostic criteria for myelodysplastic syndromes (MDS).

Frido K. Bruehl, MD, of the Mayo Clinic, and colleagues conducted the research and published their findings in the Journal of Hematopathology.

It was important to perform the research because the ICC and WHO both “proposed significant changes” to the diagnostic criteria for MDS in 2022, but the “impact of these criteria on hematopathology practice is uncertain,” the study’s authors wrote. Due to this, they evaluated the impact of the new classifications on the diagnosis of cytopenias and MDS.

Dr. Bruehl and colleagues reviewed and classified primary diagnoses of cytopenia(s)/MDS and clinical, laboratory, and pathology findings based on the ICC for Myeloid Neoplasms and Acute Leukemias and the fifth edition of the WHO Classification of Haematolymphoid Tumours: Myeloid and Histiocytic/Dendritic Neoplasms.

“The rate of major changes to the diagnosis was determined and potential pitfalls in the diagnostic approach, laboratory workflow, and clinical communication challenges were investigated,” the researchers wrote.

Dr. Bruehl and colleagues found “major changes to the diagnostic entities” occurred in 37% of cases classified per the fifth edition of the WHO classification, and in 47% of cases classified per the ICC. The differences came from five cases of MDS that were originally classified as MDS with excess blasts two (MDS-EB2) by the revised WHO fourth edition. Those five cases of MDS-EB2 were reclassified as MDS/acute myeloid leukemia in the ICC system, while they were classified as MDS with increased blasts two in the WHO fifth edition, which was not a “significant change” in classification, according to the study’s authors.

Cases of MDS with single lineage dysplasia were “not subject to major reclassification according to either system,” Dr. Bruehl and colleagues wrote. Both classifications reclassified a case of MDS with multilineage dysplasia as chronic myelomonocytic leukemia.

The new molecularly defined categories of clonal hematopoiesis with indeterminate potential or clonal hematopoiesis of uncertain potential, MDS-SF3B1, and MDS with biallelic TP53 mutations “were almost identically represented in both systems in our cohort,” the study’s authors wrote.

Overall, there “are few but important differences between the new MDS classification systems” and a “preimplementation assessment is helpful to identify diagnostic and potential clinical impacts” of the new classification systems, Dr. Bruehl and colleagues concluded.

Reference

Bruehl FK, Osman MM, Chen D, Dalland JC. The new WHO and ICC classification systems for myelodysplastic syndromes and their impact on the clinical laboratory. J Hematop. 2023. doi:10.1007/s12308-023-00538-7