Table 2 Reporting IGHV gene somatic hypermutation status in CLL

From: Immunoglobulin gene sequence analysis in chronic lymphocytic leukemia: updated ERIC recommendations

Item

Recommendations

Standard cases

 Methodology

Report type of: primers,a PCR product analysis, sequencing method, bioinformatics tools

 Gene identification

IGHV, IGHD, IGHJ genes and alleles; IGHD may be difficult to precisely identify (due to deletions and/or SHM)

 Productive rearrangement

Mutational status determined only for productive rearrangements; if unproductive, mention reasons (out-of-frame junction, stop codon)

 IGHV gene: % of nucleotide identity to germ line

Classification: U-CLL ⩾98%; M-CLL <98%; borderline CLL when 97–97.9%

 Subset identification

For subsets with well-established prognostic value (subsets #1, #2, #4 and #8)

Difficult cases (frequencyb)

 Double rearrangements (10.5%)

 

Productive+non-productive concordant status (7.8%)

Same as standard cases (mutational status defined by the productive rearrangement)

Productive+non-productive discordant status

 

 Productive U+non-productive M (0.4%)

Mutational status not determined

 Productive M+non-productive U (0.2%)

Consider as M-CLL

Double productive

 

 Concordant status (1.3%)

Same as standard cases

 Discordant status (0.7%)

Mutational status not determined

 Multiple (more than two) productive rearrangementsc

Mutational status not determined (unless it can be performed on sorted B-cell clones and predominant clones are easily identified)

 Single unproductive rearrangement (0.6%)

Mutational status not determined (after failure of alternative PCR attempts)

 Missing anchors (C104/W118) (0.4%)

Mutational status possible if evidence for IG expression on leukemic cells and/or preserved G-X-G motif in VH FR4

  1. Abbreviations: CLL, chronic lymphocytic leukemia; IG, immunoglobulin; M-CLL, mutated CLL; U-CLL, unmutated CLL.
  2. aLeader primers are the only recommended option. That said, in rare cases when leader primers are unsuccessful at providing a product that can be sequenced and VH FR1 primers are used (discouraged for the determination of SHM status), the report should indicate that the use of VH FR1 primers might underestimate the total number of IGHV somatic hypermutations as a part of the VH domain is missing.
  3. bAll frequencies according to Langerak et al.28
  4. cCases with two or more B-cell clones.32
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