On Total Least Squares Estimation for Longitudinal Errors-in-Variables Models

2021 ◽  
pp. 359-380
Author(s):  
Rauf Ahmad ◽  
Silvelyn Zwanzig
Keyword(s):  
Least Squares ◽  
Repeated Measures ◽  
Measurement Errors ◽  
Mixed Model ◽  
Linear Mixed Model ◽  
Total Least Squares ◽  
Special Focus ◽  
Design Matrix ◽  
Fixed Part ◽  
Set Up

The objective of this study is to evaluate the total least squares (TLS) estimator for the linear mixed model when the design matrix is subject to measurement errors, with special focus on models for longitudinal or repeated-measures data. We consider measurement errors only in the design matrix concerning the fixed part of the model and estimate its corresponding parameter vector under the TLS set up. After treating two variants of the general case, the random coefficient model is discussed as a special case. We evaluate conditions, on the design matrices as well as on variance component parameters, under which a reasonable TLS estimator can be expected in such models. Analysis of a real data example is also provided.

Long-term seizure outcomes after pediatric temporal lobectomy: does brain MRI lesion matter?

2019 ◽  
Vol 24 (2) ◽  
pp. 200-208
Author(s):  
Ravindra Arya ◽  
Francesco T. Mangano ◽  
Paul S. Horn ◽  
Sabrina K. Kaul ◽  
Serena K. Kaul ◽  
...  
Keyword(s):  
Repeated Measures ◽  
Mixed Model ◽  
Linear Mixed Model ◽  
Hippocampal Sclerosis ◽  
Brain Mri ◽  
Temporal Lobectomy ◽  
Seizure Freedom ◽  
Seizure Onset

OBJECTIVEThere is emerging data that adults with temporal lobe epilepsy (TLE) without a discrete lesion on brain MRI have surgical outcomes comparable to those with hippocampal sclerosis (HS). However, pediatric TLE is different from its adult counterpart. In this study, the authors investigated if the presence of a potentially epileptogenic lesion on presurgical brain MRI influences the long-term seizure outcomes after pediatric temporal lobectomy.METHODSChildren who underwent temporal lobectomy between 2007 and 2015 and had at least 1 year of seizure outcomes data were identified. These were classified into lesional and MRI-negative groups based on whether an epilepsy-protocol brain MRI showed a lesion sufficiently specific to guide surgical decisions. These patients were also categorized into pure TLE and temporal plus epilepsies based on the neurophysiological localization of the seizure-onset zone. Seizure outcomes at each follow-up visit were incorporated into a repeated-measures generalized linear mixed model (GLMM) with MRI status as a grouping variable. Clinical variables were incorporated into GLMM as covariates.RESULTSOne hundred nine patients (44 females) were included, aged 5 to 21 years, and were classified as lesional (73%), MRI negative (27%), pure TLE (56%), and temporal plus (44%). After a mean follow-up of 3.2 years (range 1.2–8.8 years), 66% of the patients were seizure free for ≥ 1 year at last follow-up. GLMM analysis revealed that lesional patients were more likely to be seizure free over the long term compared to MRI-negative patients for the overall cohort (OR 2.58, p < 0.0001) and for temporal plus epilepsies (OR 1.85, p = 0.0052). The effect of MRI lesion was not significant for pure TLE (OR 2.64, p = 0.0635). Concordance of ictal electroencephalography (OR 3.46, p < 0.0001), magnetoencephalography (OR 4.26, p < 0.0001), and later age of seizure onset (OR 1.05, p = 0.0091) were associated with a higher likelihood of seizure freedom. The most common histological findings included cortical dysplasia types 1B and 2A, HS (40% with dual pathology), and tuberous sclerosis.CONCLUSIONSA lesion on presurgical brain MRI is an important determinant of long-term seizure freedom after pediatric temporal lobectomy. Pediatric TLE is heterogeneous regarding etiologies and organization of seizure-onset zones with many patients qualifying for temporal plus nosology. The presence of an MRI lesion determined seizure outcomes in patients with temporal plus epilepsies. However, pure TLE had comparable surgical seizure outcomes for lesional and MRI-negative groups.

scholarly journals Joint modeling of multiple repeated measures and survival data using multidimensional latent trait linear mixed model

2018 ◽  
Vol 28 (10-11) ◽  
pp. 3392-3403 ◽  
Author(s):  
Jue Wang ◽  
Sheng Luo
Keyword(s):  
Survival Data ◽  
Repeated Measures ◽  
Mixed Model ◽  
Linear Mixed Model ◽  
Proportional Hazards Model ◽  
Latent Trait ◽  
Joint Modeling ◽  
Fine Motor ◽  
Terminal Event ◽  
Longitudinal Outcomes

Impairment caused by Amyotrophic lateral sclerosis (ALS) is multidimensional (e.g. bulbar, fine motor, gross motor) and progressive. Its multidimensional nature precludes a single outcome to measure disease progression. Clinical trials of ALS use multiple longitudinal outcomes to assess the treatment effects on overall improvement. A terminal event such as death or dropout can stop the follow-up process. Moreover, the time to the terminal event may be dependent on the multivariate longitudinal measurements. In this article, we develop a joint model consisting of a multidimensional latent trait linear mixed model (MLTLMM) for the multiple longitudinal outcomes, and a proportional hazards model with piecewise constant baseline hazard for the event time data. Shared random effects are used to link together two models. The model inference is conducted using a Bayesian framework via Markov chain Monte Carlo simulation implemented in Stan language. Our proposed model is evaluated by simulation studies and is applied to the Ceftriaxone study, a motivating clinical trial assessing the effect of ceftriaxone on ALS patients.

P0786CLINICAL SIGNIFICANCE AND RELATED FACTORS OF GFR SLOPE IN A LARGE MULTICENTER OBSERVATIONAL STUDY IN JAPAN

2020 ◽  
Vol 35 (Supplement_3) ◽  
Author(s):  
Yuji Kamijo ◽  
Koji Hashimoto ◽  
Yosuke Yamada ◽  
Makoto Harada ◽  
Masatsugu Aida ◽  
...  
Keyword(s):  
Linear Regression ◽  
Least Squares ◽  
Clinical Significance ◽  
Mixed Model ◽  
Linear Mixed Model ◽  
Surrogate Marker ◽  
Hazard Ratio ◽  
Related Factors ◽  
Ckd Stage ◽  
Egfr Decline

Abstract Background and Aims Recently, glomerular filtration rate (GFR) slope has attracted attention as an important surrogate marker for the prognosis of chronic kidney disease (CKD), with a reduction in slope of eGFR decline by 0.75 mL/min/1.73 m2 per year reportedly having clinical significance. As few large clinical studies on Japanese CKD patients exist, this investigation addresses the clinical significance of GFR slope and its related factors. Method To evaluate the clinical impact of GFR slope, we conducted a prognostic investigation of CKD patients in Japan by means of a large, multicenter, retrospective, observational study. Patients with CKD who were seen at among 15 general hospitals between January and March 2014 were surveyed using medical records. The selection criteria were age ≥20 years, estimated GFR (eGFR) &lt;60 mL/min/1.73 m2, and receiving medical treatment for CKD. Baseline patient characteristics, eGFR changes, and hard endpoints (death or end-stage kidney disease requiring renal replacement therapy) during observation were analysed. We calculated GFR slope using GFR data of 2 years following the observation start point by 2 calculation methods, the linear mixed model and least squares linear regression, and examined the relationship of GFR slope with the hazard ratio of the composite hard endpoints. The factors related to GFR slope were also assessed by multiple regression analysis. Results Among a total of 11233 collected patients, we analyzed the data of 7490 CKD G3 and G4 patients whose GFR data during 2 years could be obtained (60% male, mean age: 71 years, CKD G3a: 55%, G3b: 30%, G4: 15%, mean eGFR: 44.1 mL/min/1.73 m2, urine protein positive: 51%, diabetes mellitus: 49%, use of RAS inhibitors: 57%). The mean observation period was 1040 days. Hard endpoints after the GFR slope measurement period occurred in 301 subjects. The GFR slope of the cohort was -0.948 mL/min/1.73 m2 per year (95% confidence interval [CI] -1.016, -0.880) in the linear mixed model and -0.982 mL/min/1.73 m2 per year (95% CI -1.075, -0.889) according to least squares linear regression. Both calculated GFR slopes were significantly related to the hazard ratio of the composite hard endpoints. Hazard ratio decreased by 0.85 (linear mixed model) and 0.9 (least squares linear regression) times in case of a reduction in slope of eGFR decline by 0.75 mL/min/1.73 m2 per year. Multiple regression analysis revealed strongly significant associations for GFR slope with urine protein and CKD stage and undetectable relationships for GFR slope with diabetes and age. Conclusion This study demonstrated the clinical significance of GFR slope as a surrogate marker for renal prognosis in Japanese CKD patients. In order to reduce slope of eGFR decline, active intervention for proteinuria before the progression to an advanced CKD stage appears to be effective.

Position Estimation of Single Camera Visual System Based on Total Least Squares Algorithm

2012 ◽  
Vol 239-240 ◽  
pp. 1352-1355
Author(s):  
Jing Zhou ◽  
Yin Han Gao ◽  
Chang Yin Liu ◽  
Ji Zhi Li
Keyword(s):  
Visual System ◽  
Least Squares ◽  
Total Least Squares ◽  
Position Estimation ◽  
Feature Points ◽  
Perspective Theory ◽  
Optical Feature ◽  
The Matrix ◽  
Least Squares Algorithm ◽  
Set Up

The position estimation of optical feature points of visual system is the focus factor of the precision of system. For this problem , to present the Total Least Squares Algorithm . Firstly , set up the measurement coordinate system and 3D model between optical feature points, image points and the position of camera according to the position relation ; Second , build the matrix equations between optical feature points and image points ; Then apply in the total least squares to have an optimization calculation ; Finally apply in the coordinate measuring machining to have a simulation comparison experiment , the results indicate that the standard tolerance of attitude coordinate calculated by total least squares is 0.043mm, it validates the effectiveness; Compare with the traditional method based on three points perspective theory, measure the standard gauge of 500mm; the standard tolerance of traditional measurement system is 0.0641mm, the standard tolerance of Total Least Squares Algorithm is 0.0593mm; The experiment proves the Total Least Squares Algorithm is effective and has high precision.

scholarly journals Changes in Income after an Industrial Accident According to Industry and Return-to-Work Status

2019 ◽  
Vol 16 (14) ◽  
pp. 2603 ◽  
Author(s):  
Suk Won Bae ◽  
Sarah Soyeon Oh ◽  
Wha Me Park ◽  
Jaehoon Roh ◽  
Jong-Uk Won
Keyword(s):  
Return To Work ◽  
Repeated Measures ◽  
Original Work ◽  
Mixed Model ◽  
Linear Mixed Model ◽  
Service Industry ◽  
Panel Study ◽  
Work Status ◽  
Industrial Accident ◽  
Industrial Accidents

Objective: To investigate changes in the incomes of workers, particularly those in the construction sector, who experienced industrial accidents according to their status of return to work. Methods: We used data from the fifth Panel Study of Workers’ Compensation Insurance. A repeated measures ANOVA was used to compare annual differential incomes before and after the industrial accident, and a linear mixed model was used to investigate the changes in income from before to after the industrial accident according to the industry and return-to-work status. Results: A comparison of the industrial categories revealed that construction industry workers exhibited the greatest incomes before the accident and the greatest decrease in income after the industrial accident. Regression analysis for assessing changes in income after the industrial accident showed that a comparison by industry revealed a significantly greater reduction in income in the construction than service industry. A comparison by work status revealed significantly greater decreases in income in the reemployment and non-return to work groups than among those who returned to their original work. Conclusions: The economic statuses of the victims of industrial accidents decreased relative to the pre-accident statuses in all industries. The ability to return to original work is important for preserving the accident victim’s economic status.

scholarly journals Endoscopic sleeve gastroplasty, laparoscopic sleeve gastrectomy, and laparoscopic greater curve plication: do they differ at 2 years?

Endoscopy ◽  
2020 ◽  
Author(s):  
Gontrand Lopez-Nava ◽  
Ravishankar Asokkumar ◽  
Inmaculada Bautista-Castaño ◽  
Janese Laster ◽  
Anuradha Negi ◽  
...  
Keyword(s):  
Weight Loss ◽  
Sleeve Gastrectomy ◽  
Laparoscopic Sleeve Gastrectomy ◽  
Repeated Measures ◽  
Mixed Model ◽  
Linear Mixed Model ◽  
Effective Treatment Option ◽  
Endoscopic Sleeve Gastroplasty ◽  
Sleeve Gastroplasty ◽  
Laparoscopic Greater Curve Plication

Abstract Background Endoscopic sleeve gastroplasty (ESG) is an effective treatment option for obesity. However, data comparing its efficacy to bariatric surgery are scarce. We aimed to compare the effectiveness and safety of ESG with laparoscopic sleeve gastrectomy (LSG) and laparoscopic greater curve plication (LGCP) at 2 years. Methods We reviewed 353 patient records and identified 296 patients who underwent ESG (n = 199), LSG (n = 61), and LGCP (n = 36) at four centers in Spain between 2014 and 2016. We compared their total body weight loss (%TBWL) and safety over 2 years. A linear mixed model (LMM) was used to analyze repeated measures of weight loss outcomes at 6, 12, 18, and 24 months to compare the three procedures. Results Among the 296 patients, 210 (ESG 135, LSG 43, LGCP 32) completed 1 year of follow-up and 102 (ESG 46, LSG 34, LGCP 22) reached 2 years. Their mean (standard deviation [SD]) body mass index (BMI) was 39.6 (4.8) kg/m2. There were no differences in age, sex, or BMI between the groups. In LMM analysis, adjusting for age, sex, and initial BMI, we found ESG had a significantly lower TBWL, %TBWL, and BMI decline compared with LSG and LGCP at all time points (P = 0.001). The adjusted mean %TBWL at 2 years for ESG, LSG, and LGCP were 18.5 %, 28.3 %, and 26.9 %, respectively. However, ESG, when compared with LSG and LGCP, had a shorter inpatient stay (1 vs. 3 vs. 3 days; P < 0.001) and lower complication rate (0.5 % vs. 4.9 % vs. 8.3 %; P = 0.006). Conclusion All three procedures induced significant weight loss in obese patients. Although the weight loss was lower with ESG compared with other techniques, it displayed a better safety profile and shorter hospital stay.

Linear mixed model better than repeated measures analysis

2019 ◽  
Vol 30 (6) ◽  
pp. NP1-NP2 ◽  
Author(s):  
Işıl Kutluturk Karagoz ◽  
Berhan Keskin ◽  
Flora Özkalaycı ◽  
Ali Karagöz
Keyword(s):  
Mixed Models ◽  
Repeated Measures ◽  
Mixed Model ◽  
Linear Mixed Model ◽  
Linear Time ◽  
Case Series ◽  
Model Fit ◽  
Repeated Measures Analysis ◽  
Technical Issues ◽  
Better Than

We have some criticism regarding some technical issues. Mixed models have begun to play a pivotal role in statistical analyses and offer many advantages over more conventional analyses regarding repeated variance analyses. First, they allow to avoid conducting multiple t-tests; second, they can accommodate for within-patient correlation; third, they allow to incorporate not only a random coefficient, but also a random slope, typically ‘linear’ time in longitudinal case series when there are enough data and patients’ trajectories vary a lot and improving model fit.

Tone, Rhythm, and Timbre Perception in School-Age Children Using Cochlear Implants and Hearing Aids

2013 ◽  
Vol 24 (09) ◽  
pp. 789-806 ◽  
Author(s):  
Hamish Innes-Brown ◽  
Jeremy P. Marozeau ◽  
Christine M. Storey ◽  
Peter J. Blamey
Keyword(s):  
Hearing Loss ◽  
Hearing Aids ◽  
Repeated Measures ◽  
Mixed Model ◽  
Linear Mixed Model ◽  
School Age Children ◽  
Impaired Hearing ◽  
School Year ◽  
Temporal Cues ◽  
Wide Range

Background: Children with hearing impairments, especially those using hearing devices such as the cochlear implant (CI) or hearing aid (HA), are sometimes not encouraged to attend music classes, as they or their parents and teachers may be unsure whether the child can perform basic musical tasks. Purpose: The objective of the current study was to provide a baseline for the performance of children using CIs and HAs on standardized tests of rhythm and pitch perception as well as an instrument timbre identification task. An additional aim was to determine the effect of structured music training on these measures during the course of a school year. Research Design: The Intermediate Measures of Music Audiation (IMMA) Tonal and Rhythmic subtests were administered four times, with 6 wk between tests. All children in the study were also enrolled in “Music Club” teaching sessions. Measures were compared between groups and across the four testing sessions. Study Sample: Twenty children from a single school in Melbourne, Australia, were recruited. Eleven (four girls) had impaired hearing, including six with a unilateral CI or CI and HA together (two girls) and five with bilateral HAs (two girls). Nine were normally hearing, selected to match the age and gender of the hearing-impaired children. Ages ranged from 9–13 yr. Intervention: All children participated in a weekly Music Club – a 45 min session of musical activities based around vocal play and the integration of aural, visual, and kinesthetic modes of learning. Data Collection and Analysis: Audiological data were collected from clinical files. IMMA scores were converted to percentile ranks using published norms. Between-group differences were tested using repeated-measures analysis of variance, and between-session differences were tested using a linear mixed model. Linear regression was used to model the effect of hearing loss on the test scores. Results: In the first session, normally hearing children had a mean percentile rank of ˜50 in both the Tonal and Rhythmic subtests of the IMMA. Children using CIs showed trends toward lower scores in the Tonal, but not the Rhythmic, subtests. No significant improvements were found between sessions. In the timbre test, children generally made fewer errors within the set of percussive compared to nonpercussive instruments. The hearing loss level partially predicted performance in the Tonal, but not the Rhythmic, task, and predictions were more significant for nonpercussive compared to percussive instruments. Conclusions: The findings highlight the importance of temporal cues in the perception of music, and indicate that temporal cues may be used by children with CIs and HAs in the perception of not only rhythm, but also of some aspects of timbre. We were not able to link participation in the Music Club with increased scores on the Tonal, Rhythmic, and Timbre tests. However, anecdotal evidence from the children and their teachers suggested a wide range of benefits from participation in the Music Club that extended from increased engagement and interest in music classes into the children's social situations.

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