Interference in spectrophotometric analysis of cerebrospinal fluid by haemolysis induced by transport through a pneumatic tube system.

The hypothesis that sending blood-stained cerebrospinal fluid (CSF) through a pneumatic tube causes in vitro haemolysis has been tested. Spectrophotometric scanning of CSF supernatants demonstrated a significantly greater absorbance at 415 nm in those CSF samples that had been sent through the tube system compared to those that had not (P=0.0034). It is concluded that passage of blood-stained CSF down a pneumatic tube system causes in vitro haemolysis, accompanied by the release of oxyhaemoglobin from the lysed cells into the surrounding CSF. In view of this observation, it is recommended that CSF samples requiring spectrophotometric analysis, as part of the investigation of subarachnoid haemorrhage, should not be transported via a pneumatic tube system.