Algeciras‐Schimnich, Alicia

Abstract Background Interleukin 6 (IL-6) plays important roles in both innate and adaptive immunity, while dysregulated persistent production of IL-6 is involved in pathological development of various diseases associated with inflammation. Targeting the IL-6 pathway has led to many innovative treatment approaches. Siltuximab and Tocilizumab are monoclonal antibodies targeting IL-6 and IL-6 receptors respectively and have been FDA-approved for treatment of Castleman disease (Siltuximab), a rare lymphoproliferative disorder characterized by hyperproduction of IL-6 with an unknown prevalence, autoimmune diseases such as rheumatoid arthritis (Tocilizumab), and both shown potential as treatment for cytokine release syndrome in hospitalized COVID-19 patients. However, the presence of siltuximab can interfere with IL-6 assays, leading to the use of C-reactive protein (CRP) as a surrogate marker to monitor its efficacy. Aim To evaluate potential Siltuximab and Tocilizumab antibody interference on IL-6 measurements in three different IL-6 protein immunoassays. Method: Serum or EDTA plasma sample pools with different IL-6 concentrations ranging from low (2.3 – 11.1 pg/mL, around the reference interval cut-off for each assay) to high (18.5 – 1142 pg/mL), above reference interval cut-off for each assay) were utilized. Various concentrations of Siltuximab or Tocilizumab were spiked into the sample pools (at 10% of total volume) to achieve final concentrations up to 600 µg/mL and up to 300 µg/mL, respectively. Sample spiked with 10% saline were used as no-drug control. Three assays were used to measure IL-6 concentration: Beckman Access IL-6 assay on UniCel DxI 800 (Beckman Coulter), V-PLEX Plus human IL-6 assay on QuickPlex SQ120 (Meso Scale Diagnostics), and a Luminex cytokine panel assay developed in house (R&D systems) with upper reference interval limits of 6.4,1.8 and 5 pg/mL respectively. Results Siltuximab interfered with the measurement of IL-6 for all three assays. A significant interference (> 20% reduction) was observed at even a very low siltuximab concentrations in all three assays (0.05 µg/mL). In the presence of 5 µg/mL or greater Siltuximab, a maximum reduction of 93%, 83%, and 40% was observed for Beckman Access, R&D Luminex assay, and V-PLEX Plus Mesoscale assay, respectively. Tocilizumab did not interfere with the measurement of IL-6 in the three assays when serum was spiked with up to 300 µg/mL of the drug. Conclusion Siltuximab falsely reduce the measured IL-6 concentration on all three immunoassays tested in this study to differing degrees, whereas Tocilizumab does not. Consider the therapeutic range of Siltuximab (84 to 332 µg/mL) for treatment of Castleman disease, and a half-life of 20.6 days, measurement of IL-6 may not be useful in Siltuximab treated patients for an extended time-period.

Abstract INTRODUCTION The timing of plasma biomarker changes is not well understood. The goal of this study was to evaluate the temporal co‐evolution of plasma and positron emission tomography (PET) Alzheimer's disease (AD) biomarkers. METHODS We included 1408 Mayo Clinic Study of Aging and Alzheimer's Disease Research Center participants. An accelerated failure time (AFT) model was fit with amyloid beta (Aβ) PET, tau PET, plasma p‐tau217, p‐tau181, and glial fibrillary acidic protein (GFAP) as endpoints. RESULTS Individual timing of plasma p‐tau progression was strongly associated with Aβ PET and GFAP progression. In the population, GFAP became abnormal first, then Aβ PET, plasma p‐tau, and tau PET temporal meta‐regions of interest when applying cut points based on young, cognitively unimpaired participants. DISCUSSION Plasma p‐tau is a stronger indicator of a temporally linked response to elevated brain Aβ than of tau pathology. While Aβ deposition and a rise in GFAP are upstream events associated with tau phosphorylation, the temporal link between p‐tau and Aβ PET was the strongest. Highlights Plasma p‐tau progression was more strongly associated with Aβ than tau PET. Progression on plasma p‐tau was associated with Aβ PET and GFAP progression. P‐tau181 and p‐tau217 become abnormal after Aβ PET and before tau PET. GFAP became abnormal first, before plasma p‐tau and Aβ PET.

AbstractINTRODUCTIONCost‐effective screening tools for vascular contributions to cognitive impairment and dementia (VCID) has significant implications. We evaluated non‐imaging indicators of VCID using magnetic resonance imaging (MRI)‐measured white matter (WM) damage and hypothesized that these indicators differ based on age.METHODSIn 745 participants from the Mayo Clinic Study of Aging (≥50 years of age) with serial WM assessments from diffusion MRI and fluid‐attenuated inversion recovery (FLAIR)‐MRI, we examined associations between baseline non‐imaging indicators (demographics, vascular risk factors [VRFs], gait, behavioral, plasma glial fibrillary acidic protein [GFAP], and plasma neurofilament light chain [NfL]) and WM damage across three age tertiles.RESULTSVRFs and gait were associated with diffusion changes even in low age strata. All measures (VRFs, gait, behavioral, plasma GFAP, plasma NfL) were associated with white matter hyperintensities (WMHs) but mainly in intermediate and high age strata.DISCUSSIONNon‐imaging indicators of VCID were related to WM damage and may aid in screening participants and assessing outcomes for VCID.Highlights Non‐imaging indicators of VCID can aid in prediction of MRI‐measured WM damage but their importance differed by age. Vascular risk and gait measures were associated with early VCID changes measured using diffusion MRI. Plasma markers explained variability in WMH across age strata. Most non‐imaging measures explained variability in WMH and vascular WM scores in intermediate and older age groups. The framework developed here can be used to evaluate new non‐imaging VCID indicators proposed in the future.

Abstract Background Blood-based biomarkers (BBBs) are a growing area of study for improving Alzheimer’s disease (AD) clinical evaluation. BBBs have been demonstrated to correlate with AD CSF biomarkers as well as neuroimaging results for assessment of amyloid pathology. Currently BBBs may be used as a screening tool for patient selection in clinical trials, and alongside more well characterized biomarkers like amyloid-PET and CSF markers for evaluation of individuals presenting with cognitive impairment. A comparative study of several AD BBBs assays was performed to assess bias between two platforms, as well as correlation to markers of amyloid pathology. Methods The study included 146 plasma samples from 112 cognitively normal (CN), and 34 mild cognitive impairment (MCI) or AD dementia individuals. Plasma Aβ42, Aβ40, and pTau181 concentrations were obtained using the Fujirebio Lumipulse and Quanterix Simoa immunoassays. Assay comparison between Fujirebio and Quanterix were performed for Aβ42, Aβ40, Aβ42/Aβ40 ratio, pTau181, and pTau181/Aβ42 ratio using Passing-Bablok regression and regression slopes were obtained. Amyloid-PET was performed using Pittsburg Compound B, and a standard uptake value ratio (SUVR) of 1.48 was used to classify amyloid status. In the CN group, 69 were amyloid negative, and 43 were amyloid positive. In the MCI/AD dementia group, 8 were amyloid negative and 26 were amyloid positive. Spearman’s rank correlation coefficient (rho) was used to determine correlation between assays and correlation of each with Amyloid-PET SUVRs. Results Between Fujirebio (y) and Quanterix (x) assays, measured Aβ42 and Aβ40 concentrations showed a large bias with y = 5.23x − 14.25, and y = 4.42x − 264.87, respectively. A moderate to strong correlation was observed between assays for Aβ42 and Aβ40 with rho values of 0.641 (P < 0.0001), and 0.498 (P < 0.0001), respectively. The ratio of Aβ42/Aβ40 corrected this bias with y = 0.96x + 0.03 and rho = 0.509 (P < 0.0001). pTau181 showed little bias between methods with y = 0.92x + 0.48, and a rho = 0.592 (P < 0.0001). However, the pTau181/Aβ42 ratio showed a large bias driven mostly by differences in the Aβ42 concentrations with y = 0.27x + 0.04 and rho = 0.574 (P < 0.0001). Quanterix assay results correlated with amyloid-PET SUVR yielded rho coefficients of AB42/40 ratio = −0.219 (P = 0.079), pTau181 = 0.380 (P < 0.0001), and pTau181/Aβ42 ratio = 0.466 (P < 0.0001). Fujirebio assay results correlated with amyloid-PET SUVR showed AB42/40 ratio rho = −0.551 (P < 0.0001), pTau181 rho = 0.370 (P < 0.0001), and pTau181/Aβ42 ratio rho = 0.391 (P < 0.0001). Conclusion This study demonstrates that some BBBs methods differ significantly between manufacturers. Little bias was observed between the Aβ42/Aβ40 and pTau181 determinations for the evaluated platforms; however, significant bias was observed in Aβ42, Aβ40, and the pTau181/Aβ42 ratio. The Fujirebio platform demonstrated stronger correlation of the Aβ42/Aβ40 ratio with amyloid-PET SUVR, while Quanterix showed better correlation of the pTau181/Aβ42 ratio. The pTau181 assays showed similar correlation to amyloid-PET SUVR. Bias between assays as well as clinical correlation differences may preclude the generalization of clinical performance of AD BBBs assays between platforms.

Abstract Background Vasoactive intestinal peptide (VIP), a potent vasodilator, is produced by neuronal cells located in the central nervous system, the digestive, respiratory, and urogenital tracts, and the exocrine, thyroid, and adrenal glands. Increased circulating VIP is clinically useful to detect VIP-producing tumors in patients with chronic diarrheal diseases. Objective Develop a sensitive replacement radioimmunoassay (RIA) for VIP quantitation in human plasma due to the diminished supply of the antibody used in the previous in-house method. Method Patient VIP in EDTA plasma competes with labeled (125I) VIP for a limited number of primary rabbit polyclonal antibody (BMA Biomedicals, Augst, Switzerland) binding sites. Antibody-bound VIP is then complexed with a goat anti-rabbit secondary antibody and precipitated out of the solution with the use of polyethylene glycol and centrifugation. After the supernatant is discarded, the 125I signal from the pellet is counted on the Wizard2 gamma counter (Perkin Elmer, Waltham, MA). The measured signal is inversely proportional to the amount of VIP present in the patient’s sample. Method validation of the new assay included determination of imprecision (pooled human EDTA plasma), limits of detection and quantification, analytical measurement range (AMR), accuracy by spike recovery, interferences, cross-reactivity, stability, reference interval determination, and agreement with the current Mayo laboratory-developed assay. Results Stability studies on freshly collected EDTA plasma showed VIP is stable for 3 days ambient, 7 days refrigerated, and 14 days frozen. Intra-assay imprecision studies showed 8.3, 2.3, and 1.3%CV for mean VIP concentrations of 41, 144, and 304 pg/mL. Inter-assay imprecision was 12.9, 7.6, 5.2, and 7.5%CV for mean VIP concentrations of 30, 81, 180, and 308 pg/mL. The assay limit of detection was 29 pg/mL. The limit of quantitation was 30 pg/mL (%CV = 13%) and was established via precision profile. The AMR was 30–500 pg/mL (slope of 0.98, intercept of 3.0 pg/mL, and R2 of 0.97). The mean % spike recovery using a different preparation lot of calibrator material was 89% (range 83%–93%). The assay was not affected by up to 1000 mg/dL hemoglobin, 1000 mg/dL triglycerides, or 10 mg/dL bilirubin. Peptide histidine methionine 27, neurotensin, gastric inhibitory peptide, motilin, secretin, and glucagon do not cross-react in the assay. The 97.5th reference limit was <86 pg/mL (95% CI 81–90, n = 127). Positive percent agreement (PPA), negative percent agreement (NPA), and overall percent agreement (OPA) with the current Mayo VIP assay were 97, 82, and 90% respectively. Conclusion We have developed a replacement VIP RIA. This assay has a lower limit of quantitation and a broader AMR than the current assay. Concordance with the current assay was acceptable.

AbstractObjectiveThyroglobulin measurement is the cornerstone of modern management of differentiated thyroid cancer, with clinical decisions on treatment and follow-up based on the results of such measurements. However, numerous factors need to be considered regarding measurement with and interpretation of thyroglobulin assay results.DesignThe present document provides an integrated update to the 2013 and 2014 separate clinical position papers of our group on these issues.MethodsIssues concerning analytical and clinical aspects of highly-sensitive thyroglobulin measurement will be reviewed and discussed based on an extensive analysis of the available literature.ResultsThyroglobulin measurement remains a highly complex process with many pitfalls and major sources of interference, especially anti-thyroglobulin antibodies, need to be assessed, considered and, when necessary, dealt with appropriately.ConclusionsOur expert consensus group formulated 53 practical, graded recommendations for guidance on highly-sensitive thyroglobulin and TgAb in laboratory and clinical practice, especially valuable where current guidelines do not offer sufficient guidance.

AbstractINTRODUCTIONWe examined associations between plasma‐derived biomarkers of Alzheimer's disease (AD) and neuropsychiatric symptoms (NPS) in community‐dwelling older adults.METHODSCross‐sectional study involving 1005 persons ≥50 years of age (mean 74 years, 564 male, 118 cognitively impaired), who completed plasma‐derived biomarker (amyloid beta 42 [Aβ42]/Aβ40, phosphorylated tau 181 [p‐tau181], p‐tau217, total tau [t‐tau], neurofilament light [NfL]), and NPS assessment.RESULTSP‐tau181 (odds ratio [OR] 2.06, 95% confidence interval [CI] 1.41–3.00, p < 0.001), p‐tau217 (OR 1.70, 95% CI 1.10–2.61, p = 0.016), and t‐tau (OR 1.44, 95% CI 1.08–1.92, p = 0.012) were associated with appetite change. We also found that p‐tau181 and p‐tau217 were associated with increased symptoms of agitation (OR 1.93, 95% CI 1.20–3.11, p = 0.007 and OR 2.04, 95% CI 1.21–3.42, p = 0.007, respectively), and disinhibition (OR 2.39, 95% CI 1.45–3.93, p = 0.001 and OR 2.30, 95% CI 1.33–3.98, p = 0.003, respectively). Aβ42/Aβ40 and NfL were not associated with NPS.CONCLUSIONHigher plasma‐derived p‐tau181 and p‐tau217 levels are associated with increased symptoms of appetite change, agitation, and disinhibition. These findings may support the validity of plasma tau biomarkers for predicting behavioral symptoms that often accompany cognitive impairment.HIGHLIGHTS We studied 1005 community‐dwelling persons aged ≥ 50 years Higher plasma tau levels are associated with increased neuropsychiatric symptoms Aβ42/Aβ40 and NfL are not associated with neuropsychiatric symptoms Clinicians should treat neuropsychiatric symptoms in persons with high plasma‐derived tau

Abstract Blood-based biomarkers offer strong potential to revolutionize diagnosis, trial enrolment and treatment monitoring in Alzheimer’s disease (AD). However, further advances are needed before these biomarkers can achieve wider deployment beyond selective research studies and specialty memory clinics, including the development of frameworks for optimal interpretation of biomarker profiles. We hypothesized that integrating Alzheimer’s disease genetic risk score (AD-GRS) data would enhance the diagnostic value of plasma AD biomarkers by better capturing extant disease heterogeneity. Analysing 962 individuals from a population-based sample, we observed that an AD-GRS was independently associated with amyloid PET levels (an early marker of AD pathophysiology) over and above APOE ε4 or plasma p-tau181, amyloid-β42/40, glial fibrillary acidic protein or neurofilament light chain. Among individuals with a high or moderately high plasma p-tau181, integrating AD-GRS data significantly improved classification accuracy of amyloid PET positivity, including the finding that the combination of a high AD-GRS and high plasma p-tau181 outperformed p-tau181 alone in classifying amyloid PET positivity (88% versus 68%; P = 0.001). A machine learning approach incorporating plasma biomarkers, demographics and the AD-GRS was highly accurate in predicting amyloid PET levels (90% training set; 89% test set) and Shapley value analyses (an explainer method based in cooperative game theory) indicated that the AD-GRS and plasma biomarkers had differential importance in explaining amyloid deposition across individuals. Polygenic risk for AD dementia appears to account for a unique portion of disease heterogeneity, which could non-invasively enhance the interpretation of blood-based AD biomarker profiles in the population.