Stability of bilirubin and oxyhaemoglobin in cerebrospinal fluid.

Cerebrospinal fluid (CSF) is routinely investigated to diagnose subarachnoid haemorrhage (SAH) in cases with unclear neuroimaging findings. Using spectrophotometry, the levels of bilirubin and oxyhaemoglobin are analysed. This study investigates the stability for bilirubin and oxyhaemoglobin in CSF samples for up to 3 weeks measured with a spectrophotometer. The absorbances corresponding to bilirubin (455 nm) and oxyhaemoglobin (415 nm) remained fairly stable for up to 3 weeks when samples were stored at +4 °C with light protection. There was a statistically significant trend of decreased absorbance for both oxyhaemoglobin and bilirubin already after exposure to light within 120 min from sampling. It is therefore advisable to protect CSF from light until spectrophotometric analysis.