Table 1 Recommended tests for diagnostic workup of CML patients.

From: European LeukemiaNet laboratory recommendations for the diagnosis and management of chronic myeloid leukemia

 

ROUTINE DIAGNOSTIC WORKUP

EXPERIMENTAL/CLINICAL TRIALSc

Interphase FISH

• Recommended for initial screeninga

Pros: Picks up all BCR::ABL1 rearrangements irrespective of breakpoint. Usually performed on PB. May be used as primary screen for BCR::ABL1 or to investigate cases that show discrepant results between cytogenetics and RT-PCR.

Cons: does not detect ACAs or identify transcript type therefore positive cases need to be followed up by both cytogenetics and RT-PCR.

• Acceptable for initial screening

Qualitative RT-PCR

• Recommended for initial screeninga

• Strongly recommended for determining BCR::ABL1 transcript type in all confirmed CML patients

• Mandatory to detect atypical BCR::ABL1 variantsb

Pros: Only routine technique to determine exact BCR::ABL1 transcript typeb. Usually performed on PB.

Cons:. No commercial test available to detect most atypical BCR::ABL1 variants, but essential to cover atypical variants if used as a primary screen. Sequence confirmation may be required. Cannot identify ACAs therefore positive cases need to be followed up by cytogenetics. Nested RT-PCR should not generally be used due to the risk of artefacts and contamination.

• Mandatory

Cytogenetics

• Mandatory for all CML cases

Pros: Only routine technique that can detect prognostically significant ACAs. Can usually be performed on PB but may require BM. May be performed after initial screening by FISH or RT-PCR. Metaphase FISH may be useful to investigate variant translocations.

Cons: Up to 5% of CML patients have a normal karyotype therefore not recommended in isolation as an initial screening tool. Positive cases need to be followed up by RT-PCR to determine BCR::ABL1 transcript type.

• Mandatory

Quantitative RT-qPCR

• Not generally recommended

Pros: may provide additional prognostic information by providing baseline to determine early response kinetics. May be used as an initial screen for CML cases identified by FISH or cytogenetics to identify (by exclusion) those who need investigation for atypical BCR::ABL1 variants.

Cons: approach to determine early response kinetics not standardized.

• Strongly recommended

GUSB or BCR recommended as reference genes in preference to ABL1 to determine early response kinetics within the first 1-3 months

NGS panel for myeloid and lymphoid genes

• Not recommended for CP

• Suggested for de novo BP

Pros: May provide additional prognostic information and identify targets for therapy

Cons: Very limited clinical actionability, even in BC

• Strongly recommended for CP and de novo BP

ASXL1 mutations associated with adverse prognosis in some contexts but further studies required to define actionability

BCR::ABL1 TKD mutations

• Not recommended for either CP or de novo BP

Mutations very unlikely to be detected prior to TKI therapy

• Not generally recommended (but should be considered)

  1. aFISH and qualitative RT-PCR may be considered as alternative approaches for initial screening, i.e. initial identification of CML patients.
  2. bRNAseq may be a better alternative to qualitative RT-PCR but is not widely available.
  3. cDepending on trial design and objectives.
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