Differential performance of cerebrospinal fluid biomarker ratios and formulas to discriminate dementia with Lewy bodies from Alzheimer’s dementia and cognitively healthy people reflects high level of amyloidosis across dementia syndromes

Abstract

AbstractBackgroundNeurodegeneration is a common hallmark of all dementia syndromes, whereas cerebrospinal fluid amyloid‐β may reflect amyloidosis both in Alzheimer’s dementia (AD) and in dementia with Lewy bodies (DLB). It is unknown if any biomarker profiles may help discriminate DLB from AD.MethodsConsecutive outpatients with probable DLB (fourth consensus report of the DLB Consortium) were paired with outpatients with late‐onset AD (National Institute on Aging – Alzheimer’s Association) by sex, Clinical Dementia Rating and Mini‐Mental State Examination scores, and with cognitively healthy controls by sex and age (±1 year). Genotyping of rs7412 & rs429358 (APOE) was undertaken with TaqMan® Real‐Time PCR technology. Cerebrospinal fluid concentrations of amyloid‐β (Aβ42, Aβ40, Aβ38), α‐synuclein, t‐tau and p‐tau Thr181, were assessed by enzyme‐linked immunosorbent assays. The following ratios and restructured traditional regression formulas were compared among participants: Aβ42/Aβ40, Aβ42/Aβ38, t‐tau/p‐tau, t‐tau/Aβ42, p‐tau/Aβ42, α‐synuclein/Aβ42, t‐tau/α‐synuclein, (240+1.18Xt‐tau)/Aβ42, (3.694+0.0105Xt‐tau)Xp‐tau/Aβ42, (373+0.82Xt‐tau)/Aβ42, (152+8.25Xp‐tau)/Aβ42. In addition, all formulas were considered to correspond to an AD profile if >1, while t‐tau/Aβ42>0.5 and p‐tau/Aβ42>0.08 were also measured, significance at p<0.05.ResultsOverall, 27 participants with DLB (78.48±9.0 years‐old, CDR sum‐of‐boxes 10.96±3.8, eleven APOE‐ε4 carriers) were paired with 27 participants with AD (81.00±5.8 years‐old, CDR sum‐of‐boxes 10.44±3.9, twelve APOE‐ε4 carriers) and 27 controls (78.48±8.7 years‐old, CDR sum‐of‐boxes 0.30±0.8, four APOE‐ε4 carriers); two thirds were women. Only for APOE‐ε4 carriers, t‐tau/Aβ42 (p = 0.065) and t‐tau/α‐synuclein (p = 0.073) were marginally significantly higher in AD. Only for APOE‐ε4 non‐carriers, Aβ42/Aβ38 was higher (p = 0.009) and α‐synuclein/Aβ42 was lower (p = 0.043) in DLB. The t‐tau/Aβ42>0.5 (p = 0.039) and p‐tau/Aβ42>0.08 (p = 0.042) ratios were able to discriminate patients with AD from controls, but not from patients with DLB, regardless of APOE‐ε4 carrier status. All formulas were able to discriminate patients with AD from controls (p<0.02), but only (152+8.25Xp‐tau)/Aβ42>1 was able to discriminate patients with AD from patients with DLB (p = 0.025), regardless of APOE‐ε4 carrier status.ConclusionsAmyloidosis and neurodegeneration are modulated by APOE‐ε4 carrier status and may differentially affect the discriminative power of cerebrospinal fluid biomarker ratios for diagnosis of dementia syndromes. The best formula to discriminate patients with AD from patients with DLB and controls was (152+8.25Xp‐tau)/Aβ42>1. (Supported by FAPESP grant #2015/10109‐5)