missing Roche Elecsys CSF measurements between data releases

[Angela Tam]

Hi,

I'm working with the Roche Elecsys CSF data and found some discrepancies in versions that I downloaded in March 2023 (`UPENNBIOMK_MASTER_FINAL.csv`) vs April 2024 (`UPENNBIOMK_ROCHE_ELECSYS_{date}.csv`).

In the March 2023 version, we could find measurements for samples that had been processed in multiple batches (e.g. there could two measurements for ABETA42 for the same sample if it had been processed in Batch 9 and Batch12 for example). Now in the April 2024 version, we seem to find only one measurement per sample, so we can no longer see if a sample had been processed in multiple batches. In the April 2024 version, I noticed that if a sample had been processed with multiple batches (as seen in the March 2023 version), that usually the measurement acquired by the most recent batch was kept, perhaps due to ABETA40 being measured in batches after Batch 9.

I was just wondering if there's any documentation to describe the removal of measurements by multiple batches to keep only one measurement per sample in the latest release compared to previous releases? I didn't see an explanation in the Methods pdf (https://ida.loni.usc.edu/download/files/study/12d31fee-18af-4173-b72c-04aad169671a/file/adni/UPENNBIOMK_ROCHE_ELECSYS_METHODS_20231109.pdf), although there is a section that describes processing some samples with multiple batches.

Thank you for your time and help!

Angela Tam

[Danielle J Harvey]

Hi Angela,

 

Yes, it looks like there has been some selection done in the latest dataset so that there is only one value per participant per visit. I’m not entirely sure what the algorithm was – I originally thought it would use all values within the same “batch” (the batch with the most longitudinal data for a given person) – it looks like sometimes that is the case, but other times, values are selected across batches. I am hoping the Biomarker Core will provide more details soon.

 

Danielle

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