When blood is present in a CSF specimen, it is necessary to determine whether the blood is due to a traumatic puncture or to a pathologic condition. There are several clues to help make this distinction:
- More blood is present in tube 1 than in tubes 2, 3, or 4.
- When sample is centrifuged within one hour, supernatant is clear.
- Blood clots on standing.
Subarachnoid or cerebral hemorrhage:
- Blood is evenly distributed in all tubes.
- When sample is centrifuged within one hour, supernatant is pink or yellow.
- Blood does not clot on standing.