Bacterial contamination and the transport vial material affect cerebrospinal fluid concentrations of β-Amyloid and Tau protein as determined by enzyme immunoassay.

Background/aims: Determination of marker proteins of neuronal degeneration in cerebrospinal fluid (CSF) is of increasing importance. However, preanalytical problems may compromise the results.

Methods: We studied the influence of the transport tube material and shaking at room temperature on the CSF concentrations of β-amyloid and tau protein determined by enzyme immunoassays.

Results: The materials of the transport tube moderately influenced the CSF concentrations of β-amyloid and tau protein. Polyethylene and polypropylene tubes were well suited, but glass, polycarbonate and polystyrene tubes caused a decrease in the CSF β-amyloid and tau protein concentrations. The strongest impact, however, was caused by bacterial contamination of samples. Contamination with high concentrations of Pseudomonas aeruginosa and related species rendered β-amyloid undetectable and strongly diminished tau protein concentrations. The effects of several Gram-positive bacteria were less pronounced. Addition of 0.1% sodium azide prior to bacterial contamination increased the interval at which CSF could be kept at room temperature without a substantial reduction of the β-amyloid or tau protein concentration.

Conclusion: Polyethylene or polypropylene tubes are suitable transport vessels for CSF samples. Bacterial contamination during sampling and portioning must be avoided. Addition of sodium azide may be an option when transport of the sample is delayed.