Optimized Standard Operating Procedures for the Analysis of Cerebrospinal Fluid Aβ42 and the Ratios of Aβ Isoforms Using Low Protein Binding Tubes.
Reduced cerebrospinal fluid (CSF) concentration of amyloid-β1-42 (Aβ1-42) reflects the presence of amyloidopathy in brains of subjects with Alzheimer's disease (AD).



To qualify the use of Aβ1-42/Aβ1-40 for improvement of standard operating procedures (SOP) for measurement of CSF Aβ with a focus on CSF collection, storage, and analysis.



Euroimmun ELISAs for CSF Aβ isoforms were used to set up a SOP with respect to recipient properties (low binding, polypropylene), volume of tubes, freeze/thaw cycles, addition of detergents (Triton X-100, Tween-20) in collection or storage tubes or during CSF analysis. Data were analyzed with linear repeated measures and mixed effects models.



Optimization of CSF analysis included a pre-wash of recipients (e.g., tubes, 96-well plates) before sample analysis. Using the Aβ1-42/Aβ1-40 ratio, in contrast to Aβ1-42, eliminated effects of tube type, additional freeze/thaw cycles, or effect of CSF volumes for polypropylene storage tubes. 'Low binding' tubes reduced the loss of Aβ when aliquoting CSF or in function of additional freeze/thaw cycles. Addition of detergent in CSF collection tubes resulted in an almost complete absence of variation in function of collection procedures, but affected the concentration of Aβ isoforms in the immunoassay.



The ratio of Aβ1-42/Aβ1-40 is a more robust biomarker than Aβ1-42 toward (pre-) analytical interfering factors. Further, 'low binding' recipients and addition of detergent in collection tubes are able to remove effects of SOP-related confounding factors. Integration of the Aβ1-42/Aβ1-40 ratio and 'low-binding tubes' into guidance criteria may speed up worldwide standardization of CSF biomarker analysis.
ADx NeuroSciences, Gent, Belgium.
Hugo Marcel Johan
HM
Vanderstichele
Clinical Memory Research Unit, Department of Clinical Sciences, Malmö, Lund University, Sweden.
Shorena
S
Janelidze
ADx NeuroSciences, Gent, Belgium.
Leentje
L
Demeyer
IDDI, Louvain-la-Neuve, Belgium.
Els
E
Coart
ADx NeuroSciences, Gent, Belgium.
Erik
E
Stoops
Euroimmun Medizinische Labordiagnostika, Lübeck, Germany.
Victor
V
Herbst
ADx NeuroSciences, Gent, Belgium.
Kimberley
K
Mauroo
Euroimmun Medizinische Labordiagnostika, Lübeck, Germany.
Britta
B
Brix
Clinical Memory Research Unit, Department of Clinical Sciences, Malmö, Lund University, Sweden.|Memory Clinic, Skåne University Hospital, Sweden.
Oskar
O
Hansson
D000544:Alzheimer Disease / Q000134:cerebrospinal fluid* / Q000473:pathology*; D016229:Amyloid beta-Peptides / Q000134:cerebrospinal fluid*; D001921:Brain / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D008297:Male; D015233:Models, Statistical; D010446:Peptide Fragments / Q000134:cerebrospinal fluid*; D020033:Protein Isoforms / Q000134:cerebrospinal fluid*
D016229:Amyloid beta-Peptides; D010446:Peptide Fragments; D020033:Protein Isoforms; C078592:amyloid beta-protein (1-40); C075222:amyloid beta-protein (1-42)
Amyloid; ELISA; cerebrospinal fluid; improvement; standard operating procedure