What investigations are required to diagnose Myelodysplastic (MDS) syndrome?

Diagnostic Investigations for Myelodysplastic Syndrome

The diagnosis of MDS requires four mandatory investigations: peripheral blood smear with blast enumeration, bone marrow aspirate with dysplasia assessment and blast/ring sideroblast counting, bone marrow biopsy for cellularity and fibrosis evaluation, and cytogenetic analysis for chromosomal abnormalities. 1

Mandatory Core Investigations

Peripheral Blood Evaluation

• Peripheral blood smear examination is mandatory for evaluating dysplasia across all cell lines and enumerating circulating blasts 1, 2
• Count at least 200 cells on the peripheral blood smear using May-Grünwald-Giemsa staining 1, 2
• Iron staining should also be performed on blood smears 1, 2
• Look for specific dysplastic features:
  • Erythroid line: anisocytosis, poikilocytosis, basophilic stippling 1, 2
  • Myeloid line: pseudo-Pelger-Huët anomaly (nuclear hypolobation), cytoplasmic hypogranulation/degranulation, circulating blasts 1, 2
  • Megakaryocytic line: platelet anisocytosis, giant platelets 1, 2

Bone Marrow Aspirate

• Bone marrow aspirate is mandatory for comprehensive dysplasia evaluation 1
• Count at least 500 cells in bone marrow smears, including at least 100 erythroblasts and 30 megakaryocytes 1
• Use May-Grünwald-Giemsa and iron staining for morphologic assessment 1
• Enumerate blasts with critical precision (high nuclear/cytoplasmic ratio, visible nucleoli, fine nuclear chromatin) 1
• Count ring sideroblasts (≥15% is significant for classification) 1
• Assess CD34+ cells and overall cellularity 1
• Dysplasia must affect >10% of nucleated cells in the affected lineage to qualify as significant 1, 2

Bone Marrow Biopsy

• Bone marrow biopsy is mandatory for assessing marrow cellularity, fibrosis, topography, and megakaryocytic dysplasia 1
• Biopsy provides superior evaluation of megakaryocytic dysplasia compared to smears alone 1
• Essential for identifying hypocellular or fibrotic MDS variants that may be missed on aspirate 1

Cytogenetic Analysis

• Cytogenetic analysis is mandatory for detecting acquired clonal chromosomal abnormalities that allow conclusive diagnosis and prognostic assessment 1
• Recurrent abnormalities that provide presumptive evidence of MDS include: del(5q) (10-15%), monosomy 7 or del(7q) (10%), i(17q), del(12p), del(11q), del(13q), and others 1
• Approximately 50% of primary MDS patients have detectable chromosomal abnormalities 1

Recommended Additional Investigations

Flow Cytometry Immunophenotyping

• Flow cytometry is recommended for detecting abnormalities in erythroid, immature myeloid, maturing granulocytes, monocytes, and lymphoid compartments 1, 2
• Use standard methods from the International Flow Cytometry Working Group of the European LeukemiaNet 1

FISH Analysis

• FISH is recommended when standard G-banding cytogenetics repeatedly fails to yield results 1, 2
• Allows detection of targeted chromosomal abnormalities in interphase nuclei 1

Supplementary Laboratory Tests

• Complete blood count with differential, RBC indices, and reticulocyte count 1, 3
• Exclude secondary causes: RBC-folate/serum folic acid, cobalamin (B12), iron studies (iron, TIBC, ferritin) 1, 3
• Lactate dehydrogenase, bilirubin, haptoglobin to assess hemolysis 1, 3
• Viral studies: anti-HIV, anti-parvovirus B19 (especially in hypoplastic MDS), cytomegalovirus, hepatitis B antigen and anti-hepatitis C (particularly in transfusion-dependent patients) 1, 3
• Paroxysmal nocturnal hemoglobinuria clone testing 1, 3

Suggested Advanced Investigations

Molecular Genetic Testing

• Mutation analysis of candidate genes is suggested for detecting somatic mutations that allow conclusive diagnosis and reliable prognostic evaluation 1, 2
• Particularly useful when morphologic dysplasia is minimal, blast percentage is not increased, and karyotype is normal 4, 5
• Important caveat: Many older healthy individuals harbor somatic mutations in DNMT3A, TET2, and ASXL1 (clonal hematopoiesis of indeterminate potential), which can cause diagnostic uncertainty 4
• Certain mutation patterns in cytopenic patients confer high likelihood of disease progression and may allow provisional MDS diagnosis even without morphologic dysplasia 4
• Mutations also influence risk stratification and treatment selection in established MDS 4

SNP Array

• SNP array is suggested for detecting chromosomal defects at high resolution in combination with metaphase cytogenetics 1

Critical Diagnostic Pitfalls and Caveats

When Diagnosis is Uncertain

• If only unilineage dysplasia is present with normal karyotype, no blast increase, and <15% ring sideroblasts, observe for 6 months with repeat bone marrow investigation before confirming MDS diagnosis 1, 2, 3
• These patients typically present with mild cytopenia only, and rapid disease progression is unlikely 1, 3
• Repeated bone marrow examinations weeks, months, or even years apart are sometimes required to establish diagnosis 1, 3

Essential Exclusions

• The peripheral smear and bone marrow findings alone are insufficient—you must exclude other causes of cytopenia and dysplasia 2
• Rule out: aplastic anemia, hemolytic anemia, secondary anemia, idiopathic thrombocytopenic purpura, chronic neutropenia, collagen diseases, portal hypertension, disseminated intravascular coagulation 3, 6
• Exclude nutritional deficiencies (B12, folate) that can mimic dysplasia 1, 3
• Distinguish primary MDS from therapy-related MDS (prior chemotherapy, radiation, radioimmunotherapy) 3, 6

Morphologic Assessment Requirements

• All newly diagnosed patients should be evaluated at a center with specific hematologic competence to ensure comprehensive diagnostic approach 1, 3
• Morphologic dysplasia is not specific to MDS—similar features occur in pernicious anemia, acute myeloid leukemia, and other conditions 6
• Atypical MDS variants exist (hypoplastic marrow MDS, MDS with minimal dysplasia, amegakaryocytic MDS) requiring meticulous microscopic examination and careful clinical observation 6