Relationship of cerebrospinal fluid biomarkers with in vivo [11C]PIB and [18F]FDDNP binding

Objectives The purpose of this study was to investigate the relationship between cerebrospinal fluid (CSF) measurements of beta-amyloid1–42 (Aß42) and tau with both [¹¹C]PIB and [¹⁸F]FDDNP binding in patients with Alzheimer’s disease (AD), mild cognitive impairment (MCI) and healthy controls.

Methods [¹¹C]PIB and [¹⁸F]FDDNP scans, together with a lumbar puncture, were obtained in 38 subjects (15 AD, 13 MCI, 10 controls). Pearson’s correlations coefficients and linear regression analyses were used to evaluate potential associations between both CSF measures and global binding of both [¹¹C]PIB and [¹⁸F]FDDNP.

Results For both [¹¹C]PIB and [¹⁸F]FDDNP, correlations with CSF levels of Aβ42 (r=-0.71 and r=-0.37, respectively) and tau (r=0.58 and r=0.55, respectively; all p<0.001) were found across groups. Linear regression analyses showed that, adjusted for age, sex and diagnosis, global [¹¹C]PIB uptake had an inverse association with Aβ42 CSF levels (b=-0.50, p<0.001), whilst there was a positive association (b=0.60, p<0.05) between global [¹⁸F]FDDNP binding and tau CSF levels.

Conclusions The inverse association between [¹¹C]PIB and CSF Aβ42 confirms the notion that [¹¹C]PIB measures amyloid load in the brain. The positive association between [¹⁸F]FDDNP and CSF tau suggests that at least part of the specific signal of [¹⁸F]FDDNP in AD patients is due to tangles.