Setting up regional diagnostic reference levels for pediatric computed tomography in Latin America: preliminary results, challenges and the work ahead.

We established a framework for collecting radiation doses for head, chest and abdomen-pelvis computed tomography (CT) in children scanned at multiple imaging sites across Latin America with an aim towards establishing diagnostic reference levels (DRLs) and achievable doses (ADs) in pediatric CT in Latin America. Our study included 12 Latin American sites (in Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, Honduras and Panama) contributing data on the four most common pediatric CT examinations (non-contrast head, non-contrast chest, post-contrast chest and post-contrast abdomen-pelvis). Sites contributed data on patients' age, sex and weight, scan factors (tube current and potential), volume CT dose index (CTDIvol) and dose length product (DLP). Data were verified, leading to the exclusion of two sites with missing or incorrect data entries. We estimated overall and site-specific 50th (AD) and 75th (diagnostic reference level [DRL]) percentile CTDIvol and DLP for each CT protocol. Non-normal data were compared using the Kruskal-Wallis test. Sites contributed data from 3,934 children (1,834 females) for different CT exams (head CT 1,568/3,934, 40%; non-contrast chest CT 945/3,934, 24%; post-contrast chest CT 581/3,934, 15%; abdomen-pelvis CT 840/3,934, 21%). There were significant statistical differences in 50th and 75th percentile CTDIvol and DLP values across the participating sites (P<0.001). The 50th and 75th percentile doses for most CT protocols were substantially higher than the corresponding doses reported from the United States of America. Our study demonstrates substantial disparities and variations in pediatric CT examinations performed in multiple sites in Latin America. We will use the collected data to improve scan protocols and perform a follow-up CT study to establish DRLs and ADs based on clinical indications.

Vascular biomarkers and ApoE4 expression in mild cognitive impairment and Alzheimer's disease.

Vascular pathology and genetic markers such as apolipoprotein E allele ε4 (ApoE ε4) are risk factors for the progression from mild cognitive impairment (MCI) to Alzheimer's disease (AD). In Panama, a high prevalence of vascular risk factors and an increase in the aging population, generate the need to investigate biomarkers using specific, sensitive, non-invasive and cost-efficient methods that could be used in primary care. The main objective of this study was to explore the association between vascular biomarkers such as intima-media thickness (IMT) and stenosis, ApoΕ Îµ4 and cognitive function in a sample of older adults, including healthy controls (n = 41), MCI (n = 33), and AD (n = 12). A descriptive and cross-sectional study was conducted. Participants were part of the Panama Aging Research Initiative (PARI), the first prospective study in aging in Panama. Assessments included a neuropsychological battery, ApoΕ Îµ4 genotyping and a Doppler ultrasound of the left carotid artery to examine the presence of vascular risk factors. Neuropsychological tests were combined to form six cognitive domains: Global cognition, language, visuospatial abilities, learning and memory, attention and executive functions. Multivariable analyses (using age, education, and ApoE ε4 expression as covariates) were conducted. Participants with increased IMT showed poorer performance in memory and those with carotid stenosis showed poorer performance in language, visuospatial abilities and attention, independent of age, education or ApoΕ Îµ4 expression. The results support the use of vascular markers in cognitive assessments of aged individuals.