Flow Cytometry and MDS FISH Panel for Pancytopenia
Flow cytometry is recommended but not mandatory for pancytopenia workup, while cytogenetic analysis (including FISH if standard karyotyping fails) is absolutely mandatory for any suspected MDS diagnosis. 1
Mandatory Diagnostic Tests for Pancytopenia
When evaluating pancytopenia with suspected MDS, the following are required 1:
- Bone marrow aspiration and biopsy (mandatory) 1
- Conventional cytogenetics with at least 10-20 metaphases analyzed from two different cell cultures (24h and 48h) (mandatory) 1
- Complete blood count with differential and peripheral blood smear examination 1
- Bone marrow trephine biopsy for cellularity, fibrosis assessment, and additional morphologic information 1
Role of FISH Panel
FISH for MDS-specific abnormalities is strongly recommended when 1:
- Standard cytogenetics yields insufficient metaphases or normal karyotype 1
- Bone marrow is markedly hypocellular (cellularity <10%) where cytogenetic failures are common 1
- Probes should target: 5q31, cen7, 7q31, cen8, TP53, 20q, cenY 1
Cytogenetic abnormalities are present in >80% of MDS patients and have the highest prognostic value of all IPSS-R parameters 1. Chromosomes 5 and/or 7 abnormalities are particularly important as they indicate poor prognosis and may be detected by FISH even when standard karyotyping fails 1.
Role of Flow Cytometry
Flow cytometry is recommended but not mandatory for MDS diagnosis 1:
- Flow cytometry can support MDS diagnosis by detecting aberrant myeloid maturation patterns 1, 2
- It should only be performed by experts according to published guidelines 1
- Critical caveat: Flow cytometry blast percentage should never be used instead of morphologic blast counts for diagnosis or prognostic scoring 1
- Flow cytometry is particularly useful when dysplasia is subtle or equivocal 1, 2
Recent studies show flow cytometry has 87.3% sensitivity and 87.6% specificity using integrated scoring systems 3, but guidelines emphasize this remains an adjunctive tool 1.
Diagnostic Algorithm for Pancytopenia
Step 1: Exclude non-MDS causes 1:
- Vitamin B12, folate, copper deficiency
- Medications, alcohol, toxins
- Autoimmune disorders, infections
- Renal failure
- Paroxysmal nocturnal hemoglobinuria (PNH) screening with flow cytometry 1
Step 2: Obtain mandatory tests 1:
- Bone marrow aspirate with iron stain (Prussian blue)
- Bone marrow biopsy
- Conventional cytogenetics (minimum 20 metaphases) 1
Step 3: If cytogenetics fail or show normal karyotype with high clinical suspicion 1:
- Perform FISH panel for chromosomes 5q, 7,8, 20q, TP53, Y
- Consider peripheral blood FISH if bone marrow yields insufficient cells 1
Step 4: Consider flow cytometry 1, 2:
- Particularly valuable when morphologic dysplasia is subtle
- Useful for detecting aberrant CD34+ populations
- Can assess CD34+ CD7+ cells, granulocyte maturation patterns
Critical Pitfalls to Avoid
Hypocellular marrow (<10% cellularity) presents special challenges 1, 4:
- Standard cytogenetics frequently fail in markedly hypocellular specimens 1
- FISH becomes particularly valuable in this setting 1
- Hypocellular MDS can mimic aplastic anemia; monosomy 7 detected by FISH may reveal underlying MDS even when morphology is non-diagnostic 4
Flow cytometry limitations 1:
- Non-standardized methodology across laboratories 1
- Cannot replace morphologic blast assessment for IPSS scoring 1
- May show false positives in reactive conditions like aplastic anemia or PNH 3
Observation period: When dysplasia is equivocal and cytogenetics are normal, repeat bone marrow examination after 6 months is recommended before confirming MDS diagnosis 5.
Special Populations
Young patients or familial cytopenias 1: