Collection of CSF:
(1) The fluid is collected sequentially in 4 separate sterile tubes.
(2) If the specimen is not clear, then it is immediately centrifuged and the supernatant examined.
Features of traumatic specimen collection ("tap"):
(1) The amount of blood decreases progressively in the sequential tubes after the first tube is collected, with the fourth tube ideally free of blood.
(2) The supernatant is clear after centrifugation.
Features of recent hemorrhage (< 6 hours of collection):
(1) The amount of blood in subsequent tubes is comparable to that seen in the first tube.
(2) The supernatant is clear after centrifugation. If there has been hemolysis, then supernatant may be pink. (Centrifugation immediately after collection minimizes in vitro hemolysis from interfering with the interpretation).
Features of hemorrhage >= 6 hours of collection:
(1) The color of the four collection tubes are comparable to each other.
(2) The supernatant of the centrifuged specimens is xanthochromic (yellowish).
Differential diagnosis of xanthochromic (yellowish) supernatant:
(1) hemorrhage >= 6 hours prior to collection.
(2) bilirubinemia
(3) very high CSF protein
(4) carotenemia
