The analysis of nonstandard fluids, such as CSF, involves several critical issues to be resolved, including variability, instability, standardization of analytical and preanalytical procedures, and harmonization of normality values. Several studies have shown that the concentration of biomarkers has highly variable results, especially for Aβ, even using the same ELISA, leading to high variability even in cutoff values and complicating the interpretation of results among centers.

Several international initiatives aim to develop reference methods and procedures for analyzing CSF markers to achieve analytical uniformity and reproducibility among different laboratories.

The Alzheimer’s Biomarkers Standardization Initiative (ABSI) has drawn up standard operating procedures (SOP) covering all preanalytical aspects and regulating the correct processing of the sample from collection to analysis. The standards to be adopted provide for collecting CSF in sterile tubes of polypropylene, material necessary to reduce the interaction between peptides and tube, without additives. Since the material of the tubes can alter the measurement of biomarkers, it is essential to standardize the assays, adopting a common type of tubes (brand, size, etc.) to avoid differences in results; the same attention should be paid to both the tubes used for collection and those for storage. In the case of traumatic sampling, since erythrocytes may interfere with the assay, it is necessary to discard the first 1–2 mL of CSF and proceed with a new tube.

Tubes should be transported on ice and centrifuged at 2000 rpm for 10 min at 4 °C within 2 h; the supernatant should be transferred to new polypropylene tubes and stored at −20 °C, if it will be used within 2 months or at −80 °C to preserve it for more extended periods. To avoid alteration of the marker con tent, it is important to avoid several freeze/thaw cycles that may interfere with the accuracy of the assay (Fig. 1).

Fig1. Standard procedures for collecting cerebrospinal fluid for the analysis of AD biomarkers. (Copyright EDISES 2021. Reproduced with permission)

The performance of CSF examination of biomarkers often takes place in centralized laboratories, with samples collected from different hospitals in neighboring areas being shipped. This requires careful observation of preanalytical procedures to avoid affecting the validity of the test. For this reason, it is necessary to use test tubes compatible with those used in the laboratory where the analysis is carried out. If it is impossible to transport the sample immediately after col lection, the CSF can be centrifuged and frozen by dividing it into aliquots and transporting it on dry ice.

Observation of these rules prevents errors due to mishandling of samples, resulting in unreliable results, and promotes standardization among laboratories to obtain comparable biomarker results.

The final goal to be achieved is the standardization and harmonization in clinical laboratories not only of the operating procedures adopted but also of the units of measurement used, reference ranges, and decision criteria to reduce the differences among laboratories, which limit and compromise the value of guidelines, interpretation of results, and large- scale dissemination of CSF diagnostics in the field of neuro degenerative dementias.

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مرحلة ما قبل الأعراض.. دواء جديد يستهدف "شرارة" الزهايمر

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المزيد

مواضيع ذات صلة

Lab Diagnosis of Yellow fever

hexosaminidase (Hexosaminidase A, Hex A, Total hexosaminidase, Hexosaminidase A and B)

hemoglobin electrophoresis (Hgb electrophoresis)

growth hormone stimulation test (GH provocation test, Insulin tolerance test [ITT], Arginine test, Glucagon Stimulation test)

Markers of Bone Resorption: Amino and Carboxy-Terminal Telopeptides of Collagen Type I

Markers of Bone Resorption: Collagen Cross-Links

Bone Formation Markers : Osteocalcin

Diagnosis of Prion Disease

gallium scan

gallbladder nuclear scanning (Hepatobiliary scintigraphy, Cholescintigraphy, DISIDA scanning, HIDA scanning)

fluorescein angiography (FA, Ocular photography)

Bone Alkaline Phosphatase