¹²³I-FP-CIT striatal binding ratios do not decrease significantly with age in older adults.

Area of Science:

• Neurology
• Radiology
• Gerontology

Background:

• I-123-2β-Carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl)nortropane (FP-CIT) imaging is crucial for diagnosing Lewy body disease.
• Striatal binding ratios (SBRs) and Z scores are used to interpret FP-CIT scans, comparing patient uptake to normative databases.
• Age-dependency of SBRs is known, but studies often lack focus on older adults (over 60 years), who constitute the majority of patients.

Purpose of the Study:

• To investigate the relationship between SBR and age specifically in adults over 60 years.
• To evaluate the impact of age correction algorithms in commercial software on SBR Z scores in older adults.

Main Methods:

• Analyzed FP-CIT scans from 123 adults aged 60 and above, including healthy controls and those with mild cognitive impairment (MCI) or Alzheimer's disease.
• Calculated SBRs and Z scores using BRASS and DaTQUANT software.
• Applied linear mixed-effects models to assess the correlation between SBR and age, and tested the effect of disabling age correction in BRASS.

Main Results:

• No statistically significant linear relationship was found between SBR and age in adults over 60 years (slopes: -0.007 for BRASS, -0.004 for DaTQUANT).
• The observed age-related decline in SBR was less pronounced and not statistically significant compared to previous literature.
• Disabling age correction in BRASS resulted in a decrease of approximately one standard deviation in Z scores for 80-year-old individuals.

Conclusions:

• There is no significant age-related decline in SBR in individuals over 60 years without Lewy body disease.
• Standard age correction methods in commercial FP-CIT analysis software may overcorrect for age in older populations.
• Overcorrection could potentially lead to misdiagnosis in elderly patients undergoing FP-CIT imaging.