Table 1

Common terms encountered in the literature

TermDefinition
Clonal haematopoiesis of indeterminate potentialEvidence of clonality, not meeting WHO criteria for a haematological neoplasm or another clonal disorder
Age-related clonal haematopoiesisClonality in haematopoietic cells identified in elderly individuals
Clonal cytopenia of undetermined significancePersistent unexplained cytopenia(s) with evidence of clonality, not meeting WHO criteria for a haematological neoplasm
Idiopathic cytopenia of undetermined significancePersistent unexplained cytopenia(s) without significant dysplasia or evidence of clonality
Idiopathic dysplasia of undetermined significancePresence of significant dysplasia, without cytopenias or evidence of clonality
  • In the most recent WHO classification1 for MDS, cytopenia is generally defined as haemoglobin <100 g/L, platelet count <100×109/L, or neutrophil count <1.8×109/L. However, milder cytopenias are considered acceptable for MDS and recent consensus guidelines by Valent et al 27 recommend that thresholds for CH should be defined in relation to institutional reference ranges. A persistent cytopenia must be at least 4 months in duration. Dysplasia is defined as at least 10% morphological dysplasia in the myeloid, erythroid, or megakaryocytic lineages. Evidence of clonality refers to the presence of genes mutations (>2% VAF) or cytogenetic abnormalities associated with haematopoietic neoplasms.

  • CH, clonal haematopoiesis; MDS, myelodysplastic syndrome; VAF, variant allele fraction.