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:
Traumatic tap:
- 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.
As mentioned earlier in the course, distinguishing between a traumatic tap and a subarachnoid hemorrhage (SAH) may be complicated if a traumatic tap is overlying an SAH. The presence of blood in the last tube could be due to an SAH, even though the blood may be visibly less than what is observed in the first tube.
