Cholinesterase inhibitor use does not significantly influence the ability of 123I-FP-CIT imaging to distinguish Alzheimer's disease from dementia with Lewy bodies

Background: I-123- labelled 2 beta- carbomethoxy- 3 beta-( 4- iodophenyl)- N-( 3- fluoropropyl) nortropane ( I-123- FP- CIT) imaging is a diagnostic tool to help differentiate dementia with Lewy bodies ( DLB) from Alzheimer's disease ( AD). However, in animals, cholinesterase inhibitors ( ChEi) have been reported to reduce radioligand binding to the striatal dopamine transporter. As ChEi are frequently used in people with dementia, it is important to determine whether their use affects I-123- FP- CIT uptake in the striatum. Objective: To clarify whether chronic ChEi therapy modulates striatal dopamine transporter binding measured by I-123- FP- CIT in patients with AD, DLB and Parkinson's disease with dementia ( PDD). Design: Cross sectional study in 99 patients with AD ( nine on ChEi, 25 not on ChEi), DLB ( nine on ChEi, 19 not on ChEi) and PDD ( six on ChEi, 31 not on ChEi) comparing I-123- FP- CIT striatal binding ( caudate, anterior and posterior putamen) in patients receiving compared with those not receiving ChEi, correcting for key clinical variables including diagnosis, age, sex, Mini- Mental State Examination score, severity of parkinsonism and concurrent antidepressant use. Results: As previously described, I-123- FP- CIT striatal uptake was lower in DLB and PDD subjects compared with those with AD. Median duration of ChEi use was 180 days. I-123- FP- CIT uptake was not significantly reduced in subjects receiving ChEi compared those not receiving ChEi ( mean percentage reduction: AD 4.3%; DLB 0.7%; PDD 6.1%; p = 0.40). ChEi use did not differentially affect striatal (FP)-F-123- CIT uptake between patient groups ( p = 0.83). Conclusions: Use of ChEi does not significantly influence the ability of 123I- FP- CIT imaging to distinguish AD from DLB.