CD200 and Richter syndrome: In cases with CD200 MFI < 198.5, 7/152 (4.6%) patients transformed to Richter syndrome (RS), while 2/155 (1.3%) patients transformed to RS in cases with CD200 MFI ≥ 198.5 (odds ratio: 3.70, 95% CI: 0.85–18.08, p = 0.1015).