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IMPORTANCE: Visual assessment of amyloid positron emission tomographic (PET) images has been approved by regulatory authorities for clinical use. Several immunoassays have been developed to measure β-amyloid (Aβ) 42 in cerebrospinal fluid (CSF). The agreement between CSF Aβ42 measures from different immunoassays and visual PET readings may influence the use of CSF biomarkers and/or amyloid PET assessment in clinical practice and trials. OBJECTIVE: To determine the concordance between CSF Aβ42 levels measured using 5 different immunoassays and visual amyloid PET analysis. DESIGN, SETTING, AND PARTICIPANTS: The study included 262 patients with mild cognitive impairment or subjective cognitive decline from the Swedish BioFINDER (Biomarkers for Identifying Neurodegenerative Disorders Early and Reliably) cohort (recruited from September 1, 2010, through December 31, 2014) who had undergone flutemetamol F 18 ([18F]flutemetamol)–labeled PET. Levels of CSF Aβ42 were analyzed using the classic INNOTEST and the newer modified INNOTEST, fully automated Lumipulse (FL), EUROIMMUN (EI), and Meso Scale Discovery (MSD) assays. Concentrations of CSF Aβ were assessed using an antibody-independent mass spectrometry–based reference measurement procedure. MAIN OUTCOMES AND MEASURES: The concordance of CSF Aβ42 levels and Aβ42:Aβ40 and Aβ42:tau ratios with visual [18F]flutemetamol PET status. RESULTS: Of 262 participants (mean [SD] age, 70.9 [5.5] years), 108 were women (41.2%) and 154 were men (58.8%). The mass spectrometry–derived Aβ42 values showed higher correlations with the modified Aβ42-INNOTEST (r = 0.97), Aβ42-FL (r = 0.93), Aβ42-EI (r = 0.93), and Aβ42-MSD (r = 0.95) assays compared with the classic Aβ42-INNOTEST assay (r = 0.88; P ≤ .01). The signal in the classic Aβ42-INNOTEST assay was partly quenched by recombinant Aβ1-40 peptide. However, the classic Aβ42-INNOTEST assay showed better concordance with visual [18F]flutemetamol PET status (area under the receiver operating characteristic curve [AUC], 0.92) compared with the newer assays (AUCs, 0.87-0.89; P ≤ .01). The accuracies of the newer assays improved significantly when Aβ42:Aβ40 (AUCs, 0.93-0.95; P ≤ .01), Aβ42 to total tau (T-tau) (AUCs, 0.94; P ≤ .05), or Aβ42 to phosphorylated tau (P-tau) (AUCs, 0.94-0.95; P ≤ .001) ratios were used. A combination of the Aβ42:Aβ40 ratio and T-tau or P-tau level did not improve the accuracy compared with the ratio alone. CONCLUSIONS AND RELEVANCE: Concentrations of CSF Aβ42 derived from the new immunoassays (modified INNOTEST, FL, EI, and MSD) may correlate better with the antibody-independent mass spectrometry–based reference measurement procedure and may show improved agreement with visual [18F]flutemetamol PET assessment when using the Aβ42:Aβ40 or Aβ42:tau ratios. These findings suggest the benefit of implementing the CSF Aβ42:Aβ40 or Aβ42:tau ratios as a biomarker of amyloid deposition in clinical practice and trials.

AbstractThe model organism zebrafish (Danio rerio) is extensively utilized in studies of developmental biology but is also being investigated in the context of a growing list of human age-related diseases. To facilitate such studies, we here present protein expression patterns of adult zebrafish organs, including blood, brain, fin, heart, intestine, liver, and skeletal muscle. Protein extracts were prepared from the different organs of two zebrafish and analyzed using liquid chromatography coupled to high-resolution tandem mass spectrometry. Zebrafish tissue was digested directly after minimal fractionation and cleaned up (the shotgun approach). Proteins were identified using Mascot software. In total, 1394 proteins were identified of which 644 were nonredundant. Of these, 373 demonstrated an organ-specific expression pattern and 57 had not been shown on protein level before. These data emphasize the need for increased research at the protein level to facilitate the selection of candidate proteins for targeted quantification and to refine systematic genetic network analysis in vertebrate development, biology, and disease.

In pre-clinical Alzheimer’s disease, cerebral amyloid-β (Aβ) deposition precedes symptoms; Aβ-targeted therapies may have maximum benefits at this stage. Existing Aβ status measurement techniques, including amyloid PET and CSF testing, are difficult to upscale. We therefore compared the concordance of three different blood-based techniques (liquid chromatography-mass spectrometry (LC¬-MS) measures of plasma Aβ, and single molecule array (Simoa) measures of plasma Aβ and phospho-tau181 (p-tau181)) with amyloid PET-positivity in dementia-free members of Insight 46, a sub-study of the British 1946 birth cohort.Of 441 dementia-free individuals with complete data, 82 (18.6%) were amyloid PET-positive. The area under the receiver operating characteristics curve for amyloid PET status using a base model comprising age, sex and APOE ε4 carrier status was 0.695 (95% confidence interval: 0.628–0.762). The best perform- ing Simoa biomarker was p-tau181 (0.707; 0.646–0.768). LC-MS Aβ1–42/1–40 performed significantly better (0.817; 0.770–0.864), with a Youden’s index cut-point of 0.095 detecting amyloid PET-positivity with 86.6% sensitivity and 71.9% specificity. Without screening, 543 individuals would need PET scans, to obtain 100 PET-positive individuals. Screening using the base model would require 940 individuals, with 266 proceeding to scan. Using LC-MS Aβ1–42/1–40 alone would reduce these numbers to 623 and 243 respectively. Across a theoretical range of amyloid PET-positivity prevalence of 10–50%, LC-MS Aβ1–42/1–40 would consistently reduce scan numbers, with greater cost savings at lower prevalence.ashvini.keshavan@nhs.net