A traumatic puncture is distinguished by Gradual clearing of the CSF between the 1st and 4th tubes (confirmed by decreasing the red blood cell [RBC] count) Absence of xanthochromia (yellowish CSF due to lysed RBCs) in a centrifuged sample Fresh, uncrenated RBCs With intrinsic subarachnoid hemorrhage, the CSF remains uniformly bloody throughout collection; xanthochromia is often present if several hours have passed after ictus; and RBCs are usually older and crenated.