Diagnosis of CLL revisited: increased specificity by a modified five‐marker scoring system including CD200

Summary The modified Matutes score has been the basis for the diagnosis of chronic lymphocytic leukaemia ( CLL ) by flow cytometry for the past 15 years. To increase the specificity of the current score we systematically evaluated the diagnostic value of established as well as novel markers, such as CD 200, in a large cohort of patients with untreated B‐cell malignancies ( n = 370). Double positivity for CD 5 and CD 23 was of very high value to differentiate between CLL and non‐ CLL cases. In addition, lack of FMC 7 expression as well as CD 79b expression intensity showed high sensitivity (90·4% and 92·3%) with acceptable specificity (74·4% and 76·9%). For surface IgM, low or absent expression displayed poor specificity in distinguishing CLL from non‐ CLL cases (51,3%; sensitivity 83,7%). Finally, CD 200 positivity showed high sensitivity and specificity. Therefore, CD 5/ CD 23, FMC 7, CD 79b and CD 200 were included in our new CLL flow score, which retained high sensitivity (97·1% vs. 98·6% for the Matutes score, P = 0·38), but showed markedly increased specificity (87·2% vs. 53·8%, P < 0·001). These results were confirmed in our validation cohort (sensitivity 97·0% vs. 100%, P = not applicable; specificity 86·4% vs. 59·1%, P = 0·03). Our data support the use of our new CLL flow score for the diagnosis of CLL with significantly higher specificity.