Trivariate generalized non linear mixed model with transformations for meta analysis of diagnostic accuracy

2018 ◽  
Vol 13 (1) ◽  
pp. 73-83
Author(s):  
Savita Jain ◽  
Kanchan Jain ◽  
Suresh K. Sharma
Keyword(s):  
Diagnostic Accuracy ◽  
Mixed Model ◽  
Linear Mixed Model ◽  
Meta Analysis ◽  
Non Linear

Bivariate Random-effects Meta-analysis of Sensitivity and Specificity with SAS PROC GLIMMIX

2010 ◽  
Vol 49 (01) ◽  
pp. 54-64 ◽  
Author(s):  
J. Menke
Keyword(s):  
Sensitivity And Specificity ◽  
Random Effects ◽  
Mixed Model ◽  
Linear Mixed Model ◽  
Meta Analysis ◽  
Empirical Evaluation ◽  
Test Accuracy ◽  
Random Effects Model ◽  
Operating Characteristics ◽  
Meta Analyses

Summary Objectives: Meta-analysis allows to summarize pooled sensitivities and specificities from several primary diagnostic test accuracy studies. Often these pooled estimates are indirectly obtained from a hierarchical summary receiver operating characteristics (HSROC) analysis. This article presents a generalized linear random-effects model with the new SAS PROC GLIMMIX that obtains the pooled estimates for sensitivity and specificity directly. Methods: Firstly, the formula of the bivariate random-effects model is presented in context with the literature. Then its implementation with the new SAS PROC GLIMMIX is empirically evaluated in comparison to the indirect HSROC approach, utilizing the published 2 x 2 count data of 50 meta-analyses. Results: According to the empirical evaluation the meta-analytic results from the bivariate GLIMMIX approach are nearly identical to the results from the indirect HSROC approach. Conclusions: A generalized linear mixed model with PROC GLIMMIX offers a straightforward method for bivariate random-effects meta-analysis of sensitivity and specificity.

scholarly journals PSVIII-10 Effects of enzyme supplementation in corn distiller’s dried grains with solubles (DDGS) diets on growth performance in broilers: a meta-analysis

2020 ◽  
Vol 98 (Supplement_3) ◽  
pp. 211-211
Author(s):  
Jae-Cheol Jang ◽  
Zhikai Zeng ◽  
Pedro E Urriola ◽  
Gerald C Shurson
Keyword(s):  
Growth Performance ◽  
Fixed Effects ◽  
Mixed Model ◽  
Linear Mixed Model ◽  
Meta Analysis ◽  
Growth Responses ◽  
Exogenous Enzymes ◽  
The Mean ◽  
Enzyme Supplementation ◽  
Mean Differences

Abstract The objective of this study was to conduct a meta-analysis to quantitatively summarize the growth responses of broilers fed cDDGS and the efficacy of various types of dietary enzyme supplementation. A total of 12 publications with 69 observations were included in the database. Individual observations were analyzed using a multivariable linear mixed model. The mean differences (MD) of BWG, FI, and gain efficiency (G/F) were calculated by subtracting either the enzyme response in corn-soybean meal (CSB) or CSB+cDDGS based diets to the control, and was expressed as a percentage (MD = (enzyme – control)/control ×100%). A type of exogenous enzymes (xylanase; protease; carbohydrases; cocktail = proteases + carbohydrases), and feeding phase (starter = d 0 to d 21; finisher = d 21 to d 42 or 49; overall = d 0 to d 42 or more) were included as fixed effects. Dietary enzyme inclusion showed significant improvement on BWG (3.19%, P < 0.01) and G/F (5.69%, P < 0.01) in broilers fed cDDGS diet. However, no significant enzyme responses were observed in broilers fed CSB diet on growth performance. Broilers fed cDDGS diet had increased (P < 0.01) BWG with the addition of protease (3.32 %) and cocktail (3.27 %), whereas addition of xylanased improved (P < 0.01) G/F by (3.56 %) and carbohydrases (1.90 %). Broilers fed cDDGS diet with enzyme supplementation showed greater improvement in BWG (3.71 %, P < 0.01) and G/F (3.78 %, P < 0.01) at finisher phase compared with starter phase. Likewise, Broilers fed CSB diet with enzyme supplementation increased BWG (9.40 %, P < 0.01) and G/F (3.11 %, P < 0.01) at finisher phase. In conclusion, supplementation of xylanase and carbohydrases in cDDGS diet improved G/F, and the enzyme response can be maximized when fed during the finisher phase diet compared with the starter phase diet.

scholarly journals Head-to-head comparison of multiple cardiovascular magnetic resonance techniques for the detection and quantification of intramyocardial haemorrhage in patients with ST-elevation myocardial infarction

2020 ◽  
Author(s):  
Anna Giulia Pavon ◽  
Georgios Georgiopoulos ◽  
Gabriella Vincenti ◽  
Olivier Muller ◽  
Pierre Monney ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Diagnostic Accuracy ◽  
Mixed Model ◽  
Linear Mixed Model ◽  
Black Blood ◽  
Diagnostic Confidence ◽  
Poor Grade ◽  
T2 Map ◽  
T1 Map ◽  
Mapping Techniques

Abstract Objectives T2*-weighted (T2*w) is deemed as a reference standard for post-infarction intramyocardial haemorrhage (IMH). However, high proportion of T2* images is affected by off-resonance artefacts hampering image interpretation. Diagnostic accuracy and precision of alternative techniques for IMH diagnosis and quantification have been seldomly investigated. Methods and results Between April 2016 and May 2017, 50 ST-segment elevation myocardial infarction patients (66% male, 57 ± 17 years) and 15 healthy controls (60% male, 58 ± 13) were consecutively enrolled. Subjects underwent head-to-head comparison of single mid-infarct slice acquired on black-blood T2-weighted short-TI-inversion recovery (T2w-STIR), bright-blood T2prep-steady-state-free precession (T2prep-SSFP), and T2/T1 maps for IMH diagnosis and quantification against T2*w. All images were graded for quality (grade 1: very poor; grade 4: excellent) and diagnostic confidence (Likert scale, 1: very unsure and 5: highly confident). Reduced relaxation time/hypointense region (hypocore) embedded in infarct-related oedema on T2 map, T1 map, and T2w-STIR had the best overall diagnostic accuracy (per-subject: 91%, 86%, and 86%, respectively; per segment: 95%, 93%, and 93%, respectively). By mixed-effects analysis, image quality, and diagnostic confidence were higher for T2 map and T1 maps than T2*w (p < 0.05 for both scores). For IMH quantification, hypocore on T2 map and T1 map strongly correlated (Spearman’s r > 0.7, p < 0.001 for both) with IMH extent on T2*w and presented an overall excellent agreement on Bland-Altman analysis. By linear mixed model analysis, absolute hypocore size did not differ among T1-, T2 map, and T2*w. T2/T1 maps had the best intra- and inter-observer reproducibility among CMR techniques. Conclusion Hypocore on T2/T1 map is the best alternative technique to T2*w for diagnosing and quantifying IMH in post-STEMI patients. Key Point • Mapping techniques are the best alternatives for diagnosing post-infarction intramyocardial haemorrhage. • Mapping techniques are valuable tools for imaging intramyocardial haemorrhage.

scholarly journals Investigating the appropriate mode of expressing lysine requirement of fish through non-linear mixed model analysis and multilevel analysis

2012 ◽  
Vol 109 (6) ◽  
pp. 1013-1021 ◽  
Author(s):  
Katheline Hua
Keyword(s):  
Multilevel Analysis ◽  
Dietary Protein ◽  
Mixed Model ◽  
Linear Mixed Model ◽  
Model Analysis ◽  
Dietary Factors ◽  
Fish Nutrition ◽  
Mixed Model Analysis ◽  
Linear Mixed Model Analysis ◽  
Non Linear

Accurate estimates of lysine requirement are essential to fish feed formulation. However, controversy exists regarding the most appropriate mode to express lysine requirement. In the fish nutrition literature, essential amino acid (AA) requirement has been expressed as a percentage of diet, a percentage of dietary crude protein or a ratio to dietary digestible energy (DE). The controversy lies in the different assumptions regarding the effects of dietary protein and DE on lysine requirement. Non-linear mixed model analysis and multilevel analysis were carried out to investigate whether dietary protein or DE affected lysine requirement of fish. The non-linear mixed model analysis suggests that expressing lysine requirement as a percentage of dietary protein provides a better goodness of fit to the modelling dataset than expressing requirement as a fixed concentration of diet, which in turn is generally better than expressing requirement as a ratio to DE. Results from the multilevel analysis confirm that dietary protein content has a significant effect on lysine requirement, while DE does not. The findings of the present study could contribute to a better understanding of the underlying dietary factors that affect AA requirements of fish. The results of the present study could also be useful for developing nutritional guidelines and feed formulations for fish.

scholarly journals Injuries in Elite Men’s Rugby Union: An Updated (2012–2020) Meta-Analysis of 11,620 Match and Training Injuries

2021 ◽  
Author(s):  
Sean Williams ◽  
Charli Robertson ◽  
Lindsay Starling ◽  
Carly McKay ◽  
Stephen West ◽  
...  
Keyword(s):  
Incidence Rate ◽  
Mixed Model ◽  
Linear Mixed Model ◽  
Meta Analysis ◽  
Team Sports ◽  
Rugby Union ◽  
Injury Incidence ◽  
Injury Data ◽  
Analytic Review ◽  
Elite Level

Abstract Background The most recent meta-analytic review of injuries in elite senior men’s Rugby Union was published in 2013. The demands of the game at the elite level are continually changing alongside law amendments and developments in player preparation. As such, an updated meta-analysis of injury data in this setting is necessary. Objective To meta-analyse time-loss injury data in elite senior men’s Rugby Union between 2012 and 2020. Methods Electronic databases were searched using the keywords ‘rugby’ and ‘inj*’. Nineteen studies met the inclusion criteria. Injury incidence rate data were modelled using a mixed-effects Poisson regression model. Days missed data were modelled using a general linear mixed model. Results The included data encompassed a total of 8819 match injuries and 2801 training injuries. The overall incidence rate of injuries in matches was 91 per 1000 h (95% confidence interval (CI) 77–106). The estimated mean days missed per match injury was 27 days (95% CI 23–32). The overall incidence rate of match concussions was 12 per 1000 h (95% CI 9–15). The overall incidence rate of training injuries was 2.8 per 1000 h (95% CI 1.9–4.0). Playing level was not a significant effect modifier for any outcome. Conclusions The injury incidence rate and mean days missed per injury in the present meta-analysis were higher, but statistically equivalent to, the 2013 meta-analysis (81 per 1000 h and 20 days, respectively). The injury incidence rate for match injuries in elite senior men’s Rugby Union is high in comparison to most team sports, though the training injury incidence rate compares favourably. The tackle event and concussion injuries should continue to be the focus of future preventative efforts.

scholarly journals Efficacy of Acupuncture in Subpopulations with Constipation: A protocol for a Systematic Review and Individual Patient data Meta-analysis

2020 ◽  
Author(s):  
Chao Chen ◽  
Baoyan Liu ◽  
Liyun He ◽  
Xiaoying Lv ◽  
Shengnan Guo ◽  
...  
Keyword(s):  
Systematic Review ◽  
Systematic Reviews ◽  
Mixed Model ◽  
Linear Mixed Model ◽  
Individual Patient Data ◽  
Meta Analysis ◽  
Patient Data ◽  
Data Management System ◽  
Primary Analysis ◽  
Clinical Trial Registries

Abstract Background: Several systematic reviews have suggested that acupuncture is effective against constipation, but the factors predicting the effect of acupuncture in subpopulations with constipation are still unknown.Methods: We will search six major English and Chinese electronic databases and two clinical trial registries from inception for randomized controlled trials that evaluate acupuncture for constipation. Two authors will independently identify the relevant studies, extract the information from the papers, and assess the risk of bias using the Cochrane RoB 2 tool. We will contact the primary researchers of the eligible trials for individual patient data (IPD). IPD from four trials are available from the China Academy of Chinese Medical Sciences CliniRsearch Data Management System. The primary outcomes are the change in weekly complete spontaneous bowel movements. IPD from the researchers will be standardized and harmonized. A one-stage approach will be used to synthesize the IPD. Our primary analysis will examine the efficacy of acupuncture in subpopulations with constipation using a general linear mixed model.Discussion: This review will provide an IPD meta-analysis of acupuncture in constipation and demonstrate how the benefits of acupuncture may vary among subgroups of patients with constipation.Systematic review registration: International Prospective Register of Systematic Reviews (Number: CRD42020188366)

scholarly journals Laboratory Effects of COVID-19 Infection in Pregnant Women and Their Newborns: A Systematic Review and Meta-Analysis

2021 ◽  
Vol 2 ◽  
Author(s):  
Clark Zhang ◽  
Haitao Chu ◽  
Y. Veronica Pei ◽  
Jason Zhang
Keyword(s):  
Preterm Birth ◽  
Pregnant Women ◽  
Vertical Transmission ◽  
Mixed Model ◽  
Linear Mixed Model ◽  
Meta Analysis ◽  
Digital Object Identifier ◽  
Respiratory Pathogens ◽  
Neonatal Complications ◽  
Pregnant Mothers

Amidst the COVID-19 pandemic, there is a need for further research on its manifestation in pregnant women, since they are particularly prone to respiratory pathogens, like severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), due to physiological changes during pregnancy. Its effects on infants born to mothers with COVID-19 are also not well-studied, and more evidence is needed on vertical transmission of the disease from mother to infant and on the transmission of IgG/IgM antibodies between mother and infant. We aim to systematically review and evaluate the effects of COVID-19 among SARS-CoV-2-positive pregnant women in late pregnancy and neonates with SARS-CoV-2-positive pregnant mothers using blood assays to find indicators of maternal and neonatal complications. We searched for original published articles in Google Scholar, Medline (PubMed), and Embase databases to identify articles in the English language from December 2019 to July 20, 2020. Duplicate entries were searched by their titles, authors, date of publication, and Digital Object Identifier. The selected studies were included based on patient pregnancy on admission, pregnant mothers with laboratory-confirmed COVID-19 virus, maternal/neonatal complications, and blood test results. We excluded duplicate studies, articles where full text was not available, other languages than English, opinions, and perspectives. The meta-analysis using the Generalized Linear Mixed model was conducted using the “meta” and “metaprop” packages in R code. Of the 1,642 studies assessed for eligibility, 29 studies (375 mothers and neonates) were included. Preterm birth rate was 34.2%, and cesarean section rate was 82.7%. Maternal laboratory findings found elevated neutrophils (71.4%; 95% CI: 38.5–90.9), elevated CRP (67.7%; 95%: 50.6–81.1), and low hemoglobin (57.3%; 95% CI: 26.0–87.8). We found platelet count, lactate dehydrogenase, and procalcitonin to be less strongly correlated with preterm birth than between high neutrophil counts (P = 0.0007), low hemoglobin (P = 0.0188), and risk of preterm birth. There is little evidence for vertical transmission. Elevated procalcitonin levels (23.2%; 95% CI: 8.4–49.8) are observed in infants born to mothers with COVID-19, which could indicate risk for neonatal sepsis. These infants may gain passive immunity to COVID-19 through antibody transfer via placenta. These results can guide current obstetrical care during the current SARS-CoV-2 pandemic.

scholarly journals Non-linear Mixed Models in a Dose Response Modelling

2019 ◽  
Vol 1 (1) ◽  
Author(s):  
Madona Yunita Wijaya
Keyword(s):  
Linear Model ◽  
Dose Response ◽  
Mixed Model ◽  
Linear Mixed Model ◽  
Linear Models ◽  
Growth Curves ◽  
Limiting Factor ◽  
Dose Time ◽  
Non Linear ◽  
Diffusion Function

AbstractStudy designs in which an outcome is measured more than once from time to time result in longitudinal data. Most of the methodological works have been done in the setting of linear and generalized linear models, where some amount of linearity is retained. However, this still be considered a limiting factor and non-linear models is another option offering its flexibility. Non-linear model involves complexity of non-linear dependence on parameters than that in the generalized linear class. It has been utilized in many situations such as modeling of growth curves and dose-response modeling. The latter modeling will be the main interest in this study to construct a dose-response relationship, as a function of time to IBD (inflammatory bowel disease) dataset. The dataset comes from a clinical trial with 291 subjects measured during a 7 week period. Both linear and non-linear models are considered. A dose time response model with generalized diffusion function is utilized for the non-linear models. The fit of non-linear models are found to be more flexible than linear models hence able to capture more variability present in the data.Keywords: IBD; longitudinal; linear mixed model; non-linear mixed model. AbstrakDesain studi dimana hasil diukur berulang kali dari waktu ke waktu menghasilkan data longitudinal. Sebagian besar metodologi yang digunakan untuk menganalisis data longitudinal adalah model linear dan model linear umum (generalized linear model) dimana sejumlah linearitas tertentu dipertahankan. Asumsi linearitas ini masih dipandang memiliki keterbatasan dan model non-linear adalah pilihan metode lainnya yang menawarkan fleksibilitas. Model non-linear telah digunakan di berbagai macam situasi seperti model kurva pertumbuhan , model farmakokinetika, dan farmakodinamika, dan model respon-dosis. Model respon-dosis akan menjadi fokus dalam penelitian ini untuk membangun hubungan dosis-respon sebagai fungsi waktu dari data IBD dengan menggunakan model linear dan non-linear. Hasil penelitian menunjukan bahwa model non-linear lebih fleksibel daripada model linear sehingga mampu menangkap lebih banyak variabilitas yang ada di dalam data.Keywords: IBD; longitudinal; model linear; model non-linear.

scholarly journals The impact of studies with no events in both arms on meta-analysis of rare events: a simulation study using generalized linear mixed model

2021 ◽  
Author(s):  
Chang Xu ◽  
Lifeng Lin
Keyword(s):  
Effect Size ◽  
Mixed Model ◽  
Linear Mixed Model ◽  
Mean Squared Error ◽  
Meta Analysis ◽  
Unbiased Estimation ◽  
Double Zero ◽  
Squared Error ◽  
Meta Analyses ◽  
The Impact

AbstractObjectiveThe common approach to meta-analysis with double-zero studies is to remove such studies. Our previous work has confirmed that exclusion of these studies may impact the results. In this study, we undertook extensive simulations to investigate how the results of meta-analyses would be impacted in relation to the proportion of such studies.MethodsTwo standard generalized linear mixed models (GLMMs) were employed for the meta-analysis. The statistical properties of the two GLMMs were first examined in terms of percentage bias, mean squared error, and coverage. We then repeated all the meta-analyses after excluding double-zero studies. Direction of estimated effects and p-values for including against excluding double-zero studies were compared in nine ascending groups classified by the proportion of double-zero studies within a meta-analysis.ResultsBased on 50,000 simulated meta-analyses, the two GLMMs almost achieved unbiased estimation and reasonable coverage in most of the situations. When excluding double-zero studies, 0.00% to 4.47% of the meta-analyses changed the direction of effect size, and 0.61% to 8.78% changed direction of the significance of p-value. When the proportion of double-zero studies increased in a meta-analysis, the probability of the effect size changed the direction increased; when the proportion was about 40% to 60%, it has the largest impact on the change of p-values.ConclusionDouble-zero studies can impact the results of meta-analysis and excluding them may be problematic. The impact of such studies on meta-analysis varies by the proportion of such studies within a meta-analysis.

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