Table 2.

Grading of CNS disease per the COG classification system

Grade of CNS disease at diagnosis	Definition
CNS-1	No blasts in the CSF (regardless of WBC or RBC count in CSF)
CNS-2
a	<5 WBC per μL + blasts + <10 RBC per μL∗
b	<5 WBC per μL + blasts + >10 RBC per μL
c	≥5 WBC per μL + blasts + ≥10 RBC per μL; CSF WBC <2 × peripheral blood WBC
CNS-3
a	≥5 WBC per μL + blasts + <10 RBC per μL
b	≥5 WBC per μL + blasts + ≥10 RBC per μL; CSF WBC >2 × peripheral blood WBC
c	Clinical evidence of CNS disease†

Table adapted from Winick et al.²¹

^∗Constitutes a traumatic LP.

^†Includes cranial nerve palsies or other overt neurologic deficits not attributable to other causes.