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Test-retest Variability (test-retest + variability)

Distribution by Scientific Domains

Medical Sciences	100%

Selected Abstracts

18F-flutemetamol amyloid imaging in Alzheimer disease and mild cognitive impairment: A phase 2 trial

ANNALS OF NEUROLOGY, Issue 3 2010
Rik Vandenberghe MD
Objective The most widely studied positron emission tomography ligand for in vivo ,-amyloid imaging is 11C-Pittsburgh compound B (11C-PIB). Its availability, however, is limited by the need for an on-site cyclotron. Validation of the 18F-labeled PIB derivative 18F-flutemetamol could significantly enhance access to this novel technology. Methods Twenty-seven patients with early-stage clinically probable Alzheimer disease (AD), 20 with amnestic mild cognitive impairment (MCI), and 15 cognitively intact healthy volunteers (HVs) above and 10 HVs below 55 years of age participated. The primary endpoint was the efficacy of blinded visual assessments of 18F-flutemetamol scans in assigning subjects to a raised versus normal uptake category, with clinical diagnosis as the standard of truth (SOT). As secondary objectives, we determined the correlation between the regional standardized uptake value ratios (SUVRs) for 18F-flutemetamol and its parent molecule 11C-PIB in 20 of the AD subjects and 20 of the MCI patients. We also determined test-retest variability of 18F-flutemetamol SUVRs in 5 of the AD subjects. Results Blinded visual assessments of 18F-flutemetamol scans assigned 25 of 27 scans from AD subjects and 1 of 15 scans from the elderly HVs to the raised category, corresponding to a sensitivity of 93.1% and a specificity of 93.3% against the SOT. Correlation coefficients between cortical 18F-flutemetamol SUVRs and 11C-PIB SUVRs ranged from 0.89 to 0.92. Test-retest variabilities of regional SUVRs were 1 to 4%. Interpretation 18F-Flutemetamol performs similarly to the 11C-PIB parent molecule within the same subjects and provides high test-retest replicability and potentially much wider accessibility for clinical and research use. ANN NEUROL 2010 [source]

Longitudinal study of vision and retinal nerve fiber layer thickness in multiple sclerosis

ANNALS OF NEUROLOGY, Issue 6 2010
Lauren S. Talman BA
Objective Cross-sectional studies of optical coherence tomography (OCT) show that retinal nerve fiber layer (RNFL) thickness is reduced in multiple sclerosis (MS) and correlates with visual function. We determined how longitudinal changes in RNFL thickness relate to visual loss. We also examined patterns of RNFL thinning over time in MS eyes with and without a prior history of acute optic neuritis (ON). Methods Patients underwent OCT measurement of RNFL thickness at baseline and at 6-month intervals during a mean follow-up of 18 months at 3 centers. Low-contrast letter acuity (2.5%, 1.25% contrast) and visual acuity (VA) were assessed. Results Among 299 patients (593 eyes) with ,6 months follow-up, eyes with visual loss showed greater RNFL thinning compared to eyes with stable vision (low-contrast acuity, 2.5%: p < 0.001; VA: p = 0.005). RNFL thinning increased over time, with average losses of 2.9,m at 2 to 3 years and 6.1,m at 3 to 4.5 years (p < 0.001 vs 0.5,1-year follow-up interval). These patterns were observed for eyes with or without prior history of ON. Proportions of eyes with RNFL loss greater than test-retest variability (,6.6,m) increased from 11% at 0 to 1 year to 44% at 3 to 4.5 years (p < 0.001). Interpretation Progressive RNFL thinning occurs as a function of time in some patients with MS, even in the absence of ON, and is associated with clinically significant visual loss. These findings are consistent with subclinical axonal loss in the anterior visual pathway in MS, and support the use of OCT and low-contrast acuity as methods to evaluate the effectiveness of putative neuroprotection protocols. ANN NEUROL 2010;67:749,760 [source]

RTVue Fourier-domain OCT: reproducibility of RNFLT and macular thickness measurements

ACTA OPHTHALMOLOGICA, Issue 2009
A GARAS
Purpose To evaluate the reproducibility of peripapillary retinal nerve fiber layer thickness (RNFLT) and macular thickness (MT) measurements with the RTVue-100 Fourier-domain optical coherence tomography, and to determine the influence of pupil dilation, patients' experience in examinations and severity of glaucoma. Methods One eye of 14 normal subjects, 11 patients with moderate, 12 patients with severe glaucoma and 40 screening trial participants were imaged 5 times on the same day. For the hospital-based patients, the measurement series was repeated after pupil dilation and 3 months later. Results For the RNFLT and the MT parameters, intrasession intraclass correlation coefficient (ICC) varied between 93.9 and 99.0%, intrasession coefficient of variation (CV) between 1.95 and 5.69 %, and intratest variability between 3.11 and 9.13 µm. Most thickness values, all intrasession CV and intratest variability values and the signal strength index remained unchanged after pupil dilation. Most intrasession CV values increased significantly with increasing disease severity. Patients' experience in imaging examinations had no influence on intrasession CV. Intratest variability and intrasession CV represented 79.1 to 98.6 % and 77.1 to 95.0 % of test-retest variability and intervisit CV, respectively. Conclusion Reproducibility of RNFLT and MT measurement with the RTVue-100 OCT are satisfactory for clinical purposes both in normals and glaucoma patients. Pupil dilation and patients' experience in imaging examinations do not influence the reproducibility of the measurements clinically significantly. Commercial interest [source]