A4.

Rai stage system

Stage	Clinical manifestations	Risk stratification	Median survival time (month)
0	Lymphomcytosis, the number of peripheral blood lymphocyte >15×10 9/L, and lymphocyte ratio in bone marrow >40%	Low risk	>105
I	Stage 0 with lymph node enlargement	Intermediate risk	101
II	Stage 0−I with splenomegaly, hepatomegaly or both	Intermediate risk	71
III	Stage 0−II with hemoglobin <110 g/L or hematocrit <33%	High risk	19
IV	Stage 0−III with platelets <100×10 9/L	High risk	19