Estimating the optimal cutoff for the IGT-AD Distress subscale adapted for amyloid PET results disclosure.

Introduction: Research on diagnostic and biomarker disclosure has significantly increased, particularly in the field of Alzheimer's disease (AD). The psychological impact of learning amyloid positron emission tomography (PET) results has been frequently assessed using the Impact of Genetic Testing for Alzheimer's Disease (IGT-AD) instrument. Establishing an optimal cutoff score for this screening tool is essential for efficiently identifying individuals who may require psychological support after amyloid PET disclosure. In this study, we aimed to determine the optimal distress cutoff for the adapted IGT-AD instrument after amyloid PET result disclosure in cognitively symptomatic older adults.

Methods: We adapted the IGT-AD instrument by replacing reference to genetic testing with reference to amyloid PET testing. A total of 98 participants with either mild cognitive impairment (MCI) or dementia were assessed for psychological impact using this adapted instrument and the Impact of Event Scale (IES; cutoff = 26) as a gold standard. Receiver operating characteristic analysis determined the optimal distress cutoff, with the Youden index maximizing sensitivity and specificity. The area under the curve (AUC) was calculated to evaluate the predictive accuracy of the IGT-AD.

Results: The mean age of participants was 72.6 years, 41.8% were male, 77.6% were White, 16.3% were Black, and 15.3% were of Hispanic ethnicity. Most (57.2%) held bachelor or post-bachelor degrees, and 73.5% were married or cohabiting. The optimal cutoff point for the modified IGT-AD Distress subscale was determined to be 15, with a sensitivity of 100% and specificity of 70.1%. The AUC for distress was 0.89 (95% confidence interval: 0.82-0.95), indicating good predictive power.

Discussion: A distress score ≥ 15 on the adapted IGT-AD appears to be a suitable cutoff for detecting significant psychological distress in cognitively symptomatic individuals learning their amyloid PET result. This cutoff has potential clinical and research applications for screening and early intervention.

Highlights: The Impact of Genetic Testing for Alzheimer's Disease (IGT-AD) instrument is widely used to assess the psychological impact of Alzheimer's disease biomarker disclosure.Establishing a cutoff score is essential for identifying individuals needing psychological support.Receiver operating characteristic analysis determined the optimal IGT-AD distress cutoff, using Impact of Event Scale (cutoff = 26) as the gold standard.The optimal cutoff for moderate to severe distress on the adapted IGT-AD is 15.Larger studies are needed to validate this cutoff.