CLL immunophenotype scoring system

CLL immunophenotype scoring system

The immunophenotype of typical B cell CLL includes the coexpression of weak monotypic surface immunoglobulin, CD5, CD19, CD23 and weak or absent CD79B, CD22 and FMC7 (1,2).

The expression of these surface markers may vary. Hence an immunophenotypic scoring system is used for the diagnosis of CLL and to differentiate CLL from other B cell malignancies (3). Scores in CLL are usually >3, in other B-cell malignancies the scores are usually <3 (1).

With the use of this scoring system (3):

• 92% of CLL cases scored 4 or 5, 6% scored 3, 2% scored 1 or 2
• other chronic B-cell lymphomas and leukaemias scored 1 or 2, but a minority scored 3.

CD200, a glycoprotein on the surface membrane of normal B-cells, B-cell precursors, some T-cells, dendritic cells, and neurons, was first described in 2009 for being uniformly expressed in CLL, but absent in mantle cell lymphoma (MCL) (4)

A study by Jahal has assessed the value of CD200 in the differential diagnosis of different B-chronic lymphoproliferative disorders and whether it adds a discriminative potential to Matutes Score.

The modified Matutes score was calculated as described earlier (3), and positivity was established as >=30% positive cells population

• CD5 and CD23 were counted score 1 when the positive cells population was >= 30%,
• FMC7 and CD79b were considered score 1 when the positive cells population was <30%
• sIgM was considered score 1 when the expression was weak
• typical CLL cases were defined by a score >= 4 and atypical cases were identified by a score < 4
• CD200 was designated score 1 when the positive cells population was >= 30%

Sensitivity, specificity, and accuracy of Matutes scoring systems CLL versus Non-CLL differential diagnosis (4)

Jahal concluded (4):

• CD200 enhanced the diagnostic accuracy of Matutes score to 100%, and when included in a simplified 4-markers score, showed an accuracy of 99.8% compared to 99.4% of Matutes score. In conclusion, CD200 is an accurate diagnostic marker for chronic lymphocytic leukemia, and can refine the modified Matutes score accuracy when added with other markers.

Reference:

1. Oscier D et al. Guidelines on the diagnosis and management of chronic lymphocytic leukaemia. Br J Haematol. 2004;125(3):294-317
2. Moreau EJ, Matutes E, A’Hern RP, Morilla AM, Morilla RM, Owusu-Ankomah KA, et al. Improvement of the chronic lymphocytic leukemia scoring system with the monoclonal antibody SN8 (CD79b). Am J Clin Pathol. 1997; 108(4):378-82
3. Yee KW, O'Brien SM. Chronic lymphocytic leukemia: diagnosis and treatment. Mayo Clin Proc. 2006;81(8):1105-29.
4. Jalal SD. The contribution of CD200 to the diagnostic accuracy of Matutes score in the diagnosis of chronic lymphocytic leukemia in limited resources laboratories. PLoS ONE 2021 16(2): e0247491. https://doi.org/10.1371/journal. pone.0247491