Version

This documentation pertains to Freeze 2023_May of the Roche Elecsys IVD - Madison dataset.

Origin

These cerebrospinal fluid assay results come from the laboratory of Sterling Johnson.


Analytes:

• Amyloid beta 42 [Gen1]
• Amyloid beta 42 [Gen2]
• Phosphorylated tau 181
• Total tau

Derived variables:

• ptau181/Ab42 [Crosswalked]
• Ab42 binary [Crosswalked]
• ptau181/Ab42 binary [Crosswalked]
• ptau181/Ab42 [Gen1]
• Ab42 binary [Gen1]
• ptau181/Ab42 binary [Gen1]
• ptau181 binary
  
  

Detection Limits:

• Ab42 [Gen1]: 200-1700 pg/mL
• Ab42 [Gen2]: 150-2500 pg/mL
• ptau181: 8-120 pg/mL
• ttau: LLOQ 80 pg/mL

Methods:

In mid 2022, a new version of the Ab42 assay was released that has superior detection limits. Our site began using this assay in September 2022. As part of the adoption of the new assay, we ran a small study on N=89 samples in Sarstedt tubes that had been previously analyzed with the Gen1 Ab42 assay (the crosswalk sample). These were selected to have good representation of both WRAP and ADRC cohorts, and a distribution of analyte values mapping well to the overall distribution in this tube type (including a sizeable number whose Ab42 exceeded the Gen1 ULOQ). The results of this small crosswalk study suggested good correspondence between Gen1 and Gen2, with an intraclass correlation of 0.89 for all samples, and 0.94 for those with Gen1 values that were not truncated at the ULOQ. Those with in-range Gen1 values were used to develop a linear equation imputing the Gen2 value for a sample on the basis of its Gen1 measurement alone. Then, this equation was applied to samples that were not part of the crosswalk sample, in order to be able to put old and new measurements on a common scale. The imputed values from those measured with only Gen1 are combined with measured Gen2 values in the columns ending in .xw.

Binary cutpoints for Gen2 Ab42 and ptau181/Ab42 were derived in a similar method to that used in the paper, "Pre-analytic factors affecting Elecsys cobas e 601 CSF biomarkers in Alzheimer’s disease" (Jonaitis et al., submitted). For the crosswalked and Gen2 binary columns, the Gen2 thresholds were applied to both raw and imputed values. For the Gen1 binary columns, the thresholds described in Jonaitis et al. were applied.

Data Sheets

1. Electrochemiluminescence immunoassay (ECLIA) for the in vitro quantitative determination of phosphorylated Tau in human Cerebrospinal fluid (CSF). Published online 2017. URL: https://diagnostics.roche.com/global/en/products/params/elecsys-ptau.html
   
   
2. Electrochemiluminescence immunoassay (ECLIA) for the in vitro quantitative determination of ß-Amyloid (1-42) in human Cerebrospinal fluid (CSF). Published online 2017. URL: https://diagnostics.roche.com/global/en/products/params/elecsys-abeta42.html
   
   
3. Electrochemiluminescence immunoassay (ECLIA) for the in vitro quantitative determination of total Tau in human Cerebrospinal fluid (CSF). Published online 2017. URL: https://diagnostics.roche.com/global/en/products/params/elecsys-ttau.html

Data Dictionary  

Funding / Acknowledgments

Papers including data obtained from these assays should acknowledge NIH R01 AG027161 (the Wisconsin Registry for Alzheimer's Prevention) and/or NIH P30 AG062715 (the Wisconsin Alzheimer's Disease Research Center).