Table 2. Common diagnostic and... | American Society of Hematology

Table 2.

Common diagnostic and interpretative challenges with NGS-based MRD for IG/TR

Challenge	Possible solution(s)
No diagnostic sample is available	Alternative methods of MRD assessment that do not require a diagnostic sample should be used (eg, MFC for Ph-negative ALL or RT-PCR for BCR::ABL1)
The patient has no BM involvement (ie, extramedullary-only disease)	Baseline clonotyping can be performed on FFPE slides from the tumor and subsequent MRD testing may be performed in the PB
A suitable sequence for MRD tracking could not be identified	Ensure that a sample representative of the disease process (eg, active morphological disease) was sent for baseline clonotyping Consider sending a second, high quality sample for repeat baseline assessment For patients with B-cell ALL without a dominant sequence, sequencing of TR gene rearrangements should be requested, as this may identify a trackable sequence in some patients In some cases (eg, ETP ALL), a trackable clonotype is not present in the leukemic clone and alternative MRD methodologies should be used.
MRD-negative report in a sample with poor DNA/cellular input	Consider repeating MRD testing after a short interval to obtain a high-quality remission sample, particularly in patients with high risk of relapse
MRD detected below the LOD	When multiple trackable sequences are available, the MRD assessment for each sequence should be evaluated in the context of their individual LOD and uniqueness IGH sequences generally are more unique and thus carry more prognostic significance than IGK/IGL sequences (although in some cases IGK/IGL sequences may be more unique, as represented by a lower LOD) For samples with MRD below the LOD for which only relatively nonunique sequences are trackable, the dynamics of these MRD values (rather than the value from an individual report) may be helpful in distinguishing true MRD from background.
Detection of a “new dominant sequence”	When not present in the original diagnostic sample, the sequences often represent expanding sequences not associated with the original malignancy and usually should not affect prognostication or therapeutic decisions.
Interpretive issues related to the MRD report that are not adequately answered above	Consult an expert and/or the diagnostic laboratory (eg, Adaptive Biotechnologies for the clonoSEQ assay) for assistance.

Challenge	Possible solution(s)
No diagnostic sample is available	Alternative methods of MRD assessment that do not require a diagnostic sample should be used (eg, MFC for Ph-negative ALL or RT-PCR for BCR::ABL1)
The patient has no BM involvement (ie, extramedullary-only disease)	Baseline clonotyping can be performed on FFPE slides from the tumor and subsequent MRD testing may be performed in the PB
A suitable sequence for MRD tracking could not be identified	Ensure that a sample representative of the disease process (eg, active morphological disease) was sent for baseline clonotyping Consider sending a second, high quality sample for repeat baseline assessment For patients with B-cell ALL without a dominant sequence, sequencing of TR gene rearrangements should be requested, as this may identify a trackable sequence in some patients In some cases (eg, ETP ALL), a trackable clonotype is not present in the leukemic clone and alternative MRD methodologies should be used.
MRD-negative report in a sample with poor DNA/cellular input	Consider repeating MRD testing after a short interval to obtain a high-quality remission sample, particularly in patients with high risk of relapse
MRD detected below the LOD	When multiple trackable sequences are available, the MRD assessment for each sequence should be evaluated in the context of their individual LOD and uniqueness IGH sequences generally are more unique and thus carry more prognostic significance than IGK/IGL sequences (although in some cases IGK/IGL sequences may be more unique, as represented by a lower LOD) For samples with MRD below the LOD for which only relatively nonunique sequences are trackable, the dynamics of these MRD values (rather than the value from an individual report) may be helpful in distinguishing true MRD from background.
Detection of a “new dominant sequence”	When not present in the original diagnostic sample, the sequences often represent expanding sequences not associated with the original malignancy and usually should not affect prognostication or therapeutic decisions.
Interpretive issues related to the MRD report that are not adequately answered above	Consult an expert and/or the diagnostic laboratory (eg, Adaptive Biotechnologies for the clonoSEQ assay) for assistance.

ETP, early T-cell precursor; FFPE, formalin-fixed paraffin-embedded; IGH, immunoglobulin heavy-chain.