Abstract
The core cerebrospinal fluid (CSF) biomarkers Aβ42, total-tau and phospho-tau are promising as diagnostic markers and as markers of treatment effects, but inter-laboratory variation, especially for CSF Aβ42, lowers their usability. Here, we discuss the causes of these variations and present a global quality control (QC) program to overcome them. The program is run by the Clinical Neurochemistry Laboratory in Gothenburg, Sweden in conjunction with the Alzheimer's Association. Both research and clinical CSF laboratories, as well as pharmaceutical companies, are enrolled in the program. The program is open for generally (commercially) available assay formats, but not for in-house assays, and consists of two parts. The first part involves a standardized flow chart for lumbar puncture and CSF processing. The second part is an external quality control program, in which samples (aliquots of pooled CSF) are sent out three times per year to the participating laboratories for CSF biomarker analysis, after which biomarkers levels are entered into a report form and returned. At present, the program has over 40 participants from all over the world. The final report for each QC round includes information on the measured biomarker levels for the individual laboratory and, for comparison, the mean and variation in biomarker levels across all laboratories involved in the program. In addition, the longitudinal stability in CSF biomarker levels for the individual laboratory, expressed as percent deviation over time, will be reported. These reports serve as feedback for the participating laboratories, to identify whether the level of a biomarker is outside an acceptable range and to note sudden changes or longitudinal drifts in CSF biomarker levels. By July 2010 two QC rounds will have been completed. Data from these will be shown and discussed. Experience from routine clinical chemistry shows that the most effective way of identifying and overcoming inter-laboratory variation is to establish QC programs with large numbers of participants. Such a program is now at hand for biochemical AD biomarkers. The first QC rounds will identify problems. Following QC rounds will reveal whether we have managed to solve them or not.
Published Version
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