Three 24-Hour Recalls in Comparison with One Improve the Estimates of Energy and Nutrient Intakes in an Urban Mexican Population.

BACKGROUND: Population surveys often collect dietary intake data by using one or two 24-h recalls (24HR), mainly to minimize cost and respondent burden. However, in order to increase accuracy in estimating usual intake distributions, a larger number of 24HRs may be advisable. OBJECTIVE: The purpose of this study was to identify whether estimates of the intake and prevalence of nutrient inadequacy based on 3 d are better than those that are based on 1 d of information. METHODS: We conducted a national survey in 31 cities in Mexico using a sample that included 1073 individuals of both sexes, from birth through 79 y of age. Dietary information was collected by using 3 multiple-pass 24HRs (on nonconsecutive days). We estimated intake, adequacy, and prevalence of energy and nutrient inadequacy using information from 1 d and also from 3 d, adjusted for day-to-day variability, using PC-SIDE software. The prevalence of inadequacy was estimated by using the reference values proposed by the US Institute of Medicine. RESULTS: We found high prevalences of inadequacy for fiber (73-99%), iron (31-94%), calcium (2-85%), vitamin A (0.1-61%), and folates (2-80%) among various age and sex groups. Energy intake results showed that the variance in the estimated usual 3-d intake distribution was smaller than the variance of distribution estimated from a single daily intake. We observed bigger differences in prevalence of inadequacy between 1 and 3 d for several nutrients. For example, in preschool children, the prevalence of inadequacy of folate and calcium was 30% and 43%, respectively, with 1-d recalls and 3.7% and 4.6%, respectively, with 3-d recalls. CONCLUSIONS: We conclude that the adjusting-by-variance method using 3 d of 24HR allows for a more accurate estimation of usual intake, dietary adequacy, and prevalence of inadequacy, thereby reducing the measurement error that could compromise the results and conclusions of surveys.

Patient-specific detection of perfusion abnormalities combining within-subject and between-subject variances in Arterial Spin Labeling.

In this paper, patient-specific perfusion abnormalities in Arterial Spin Labeling (ASL) were identified by comparing a single patient to a group of healthy controls using a mixed-effect hierarchical General Linear Model (GLM). Two approaches are currently in use to solve hierarchical GLMs: (1) the homoscedastic approach assumes homogeneous variances across subjects and (2) the heteroscedastic approach is theoretically more efficient in the presence of heterogeneous variances but algorithmically more demanding. In practice, in functional magnetic resonance imaging studies, the superiority of the heteroscedastic approach is still under debate. Due to the low signal-to-noise ratio of ASL sequences, within-subject variances have a significant impact on the estimated perfusion maps and the heteroscedastic model might be better suited in this context. In this paper we studied how the homoscedastic and heteroscedastic approaches behave in terms of specificity and sensitivity in the detection of patient-specific ASL perfusion abnormalities. Validation was undertaken on a dataset of 25 patients diagnosed with brain tumors and 36 healthy volunteers. We showed evidence of heterogeneous within-subject variances in ASL and pointed out an increased false positive rate of the homoscedastic model. In the detection of patient-specific brain perfusion abnormalities with ASL, modeling heterogeneous variances increases the sensitivity at the same specificity level.

Repeatability of radiotherapy dose-painting prescriptions derived from a multiparametric magnetic resonance imaging model of glioblastoma infiltration.

Background and purpose: Glioblastoma (GBM) patients have a dismal prognosis. Tumours typically recur within months of surgical resection and post-operative chemoradiation. Multiparametric magnetic resonance imaging (mpMRI) biomarkers promise to improve GBM outcomes by identifying likely regions of infiltrative tumour in tumour probability (TP) maps. These regions could be treated with escalated dose via dose-painting radiotherapy to achieve higher rates of tumour control. Crucial to the technical validation of dose-painting using imaging biomarkers is the repeatability of the derived dose prescriptions. Here, we quantify repeatability of dose-painting prescriptions derived from mpMRI. Materials and methods: TP maps were calculated with a clinically validated model that linearly combined apparent diffusion coefficient (ADC) and relative cerebral blood volume (rBV) or ADC and relative cerebral blood flow (rBF) data. Maps were developed for 11 GBM patients who received two mpMRI scans separated by a short interval prior to chemoradiation treatment. A linear dose mapping function was applied to obtain dose-painting prescription (DP) maps for each session. Voxel-wise and group-wise repeatability metrics were calculated for parametric, TP and DP maps within radiotherapy margins. Results: DP maps derived from mpMRI were repeatable between imaging sessions (ICC > 0.85). ADC maps showed higher repeatability than rBV and rBF maps (Wilcoxon test, p = 0.001). TP maps obtained from the combination of ADC and rBF were the most stable (median ICC: 0.89). Conclusions: Dose-painting prescriptions derived from a mpMRI model of tumour infiltration have a good level of repeatability and can be used to generate reliable dose-painting plans for GBM patients.

Within-subject haemoglobin variation in elite athletes: a longitudinal investigation of 13 887 haemoglobin concentration readings.

The Athlete Biological Passport (ABP) estimates individualized reference ranges for key blood markers, such as haemoglobin concentration ([Hb]), using predetermined population mean, between- and within-subject variances. Here, we aim to reassess previously published estimates for within-subject [Hb] variance and determine whether sex-, analyzer-, sport-, or season-specific values are required. Our reference population contains 7723 male (mean ± SD, 22.3 ± 4.6 years of age) and 6164 female (21.6 ± 4.3) athlete observations from 49 sports. [Hb] was calculated using one of three cytometers; Bayer-H3 (1997-1999, n = 4554), ADVIA-120 (1999-2010, n = 8636) and Sysmex XT-2000i (2010-2012, n = 697). The final model was a linear mixed model for [Hb] with analyzer (H3, ADVIA, Sysmex), sex (male, female), sport (power-endurance, endurance, skill, team, disabled and non-athletes), season (summer, winter), and the interaction between sex and sport as fixed effects and athlete as a random effect. The model included an exponential correlation structure to allow for within-subject autocorrelation, and allowed different within-subject variances for each sport. Within-subject [Hb] variance (g(2) /L(2) ) was significantly less for power endurance (35.09, 95% CI 33.50 to 36.76), disabled (25.82, 95% CI 21.71 to 35.28) and non-athletes (34.30, 95% CI 28.53 to 35.87) than for endurance (40.35, 95% CI 39.62 to 47.22) and team sports (38.70, 95% CI 37.68 to 39.76) athletes. No new evidence was found to justify adjusting the current within-subject [Hb] variance estimate.