Cerebrospinal Fluid Biomarker Analysis for Alzheimer's Diagnosis

The details of the CSF sample collection and analytic processing are described elsewhere⁴ (Shaw et al., 2009 (link)). For the AT (N) grouping of the ADNI cohort based on CSF values, we used the archived data set “UPENNBIOMK_MASTER.csv.” A cutoff value of 192 pg./ml was used to determine Aβ42 status in CSF, a cutoff value of 23 pg./ml was used for pTau181 status, and a cutoff value of 93 pg./ml was used for tTau status (Shaw et al., 2009 (link)). If multiple CSF values were reported at baseline, we used the median value of these results. The details of CSF sample collection, analytical processing, and cutoff values for the Erlangen cohort are described elsewhere (Oberstein et al., 2022 (link)). In short, the cut-offs were calculated by maximizing the respective Youden index of results of the different ELISAs for Aβ42, pTau, and tTau in CSF. A cut-off value of 0.05 was used for the determination of the status of the Aβ42/Aβ40 ratio, a cut-off value of 600 pg./ml (INNOTEST^®, Innogenetics) or 620 pg./ml (IBL) for Aβ42 status, a cut-off value of 60 pg./ml (INNOTEST^®, Innogenetics) and 50 pg./ml (INNOTEST^®, Fujirebio) for pTau181 status, and a cut-off value of 320 (INNOTEST^®, Fujirebio) or 300 pg./ml (INNOTEST^®, Innogenetics) for tTau status.