A transition copula model for analyzing multivariate longitudinal data with missing responses.

In multivariate longitudinal studies, several outcomes are repeatedly measured for each subject over time. The data structure of these studies creates two types of associations which should take into account by the model: association of outcomes at a given time point and association among repeated measurements over time for a specific outcome. In our approach, because of some advantageous arisen from features like flexibility of marginal distributions, a copula-based approach is used for joint modeling of multivariate outcomes at each time points, also a transition model is used for considering the association of longitudinal measurements over time. For the problem of incomplete data, missingness mechanism is assumed to be ignorable. Some simulation results are reported in different scenarios using the Gaussian, t and several commonly used copulas of the family of Archimedean copulas. Akaike information criterion (AIC) is used to select the best copula function. The proposed approach is also used for analyzing a real obesity data set.

A Bayesian shared parameter model for joint modeling of longitudinal continuous and binary outcomes.

Joint modeling of associated mixed biomarkers in longitudinal studies leads to a better clinical decision by improving the efficiency of parameter estimates. In many clinical studies, the observed time for two biomarkers may not be equivalent and one of the longitudinal responses may have recorded in a longer time than the other one. In addition, the response variables may have different missing patterns. In this paper, we propose a new joint model of associated continuous and binary responses by accounting different missing patterns for two longitudinal outcomes. A conditional model for joint modeling of the two responses is used and two shared random effects models are considered for intermittent missingness of two responses. A Bayesian approach using Markov Chain Monte Carlo (MCMC) is adopted for parameter estimation and model implementation. The validation and performance of the proposed model are investigated using some simulation studies. The proposed model is also applied for analyzing a real data set of bariatric surgery.

Gastric remnant perforation due to trocar site herniation after laparoscopic Roux-en-Y gastric bypass.

A 39-year-old woman was admitted with colicky left upper-quadrant pain, dyspnoea, low-grade fever, tachycardia and a subtle left upper-quadrant tenderness without leucocytosis. Computed tomography revealed a distended gastric remnant due to small-bowel loop herniation at the trocar site. The patient underwent a diagnostic laparoscopy as her general condition worsened. Perforation across the staple line was seen and repaired. The postoperative period was uneventful. As a rare complication of laparoscopic Roux-en-Y gastric bypass, small-bowel obstruction is of great importance because it can lead to gastric remnant perforation if not managed correctly. There have been rare reports of trocar site herniation as a cause of small-bowel obstruction following laparoscopic Roux-en-Y gastric bypass. Prompt diagnostic laparoscopy should be considered. This is the first case reported in which the excluded stomach was perforated due to trocar site herniation of the small-bowel loop. It should be noted that the tissue around the perforation is fragile and proper tension should be employed when it is repaired. Generally, an omental patch is not encouraged.

Accelerated wound healing in a diabetic rat model using decellularized dermal matrix and human umbilical cord perivascular cells.

There is an unmet clinical need for novel wound healing strategies to treat full thickness skin defects, especially in diabetic patients. We hypothesized that a scaffold could perform dual roles of a biomechanical support and a favorable biochemical environment for stem cells. Human umbilical cord perivascular cells (HUCPVCs) have been recently reported as a type of mesenchymal stem cell that can accelerate early wound healing in skin defects. However, there are only a limited number of studies that have incorporated these cells into natural scaffolds for dermal tissue engineering. The aim of the present study was to promote angiogenesis and accelerate wound healing by using HUCPVCs and decellularized dermal matrix (DDM) in a rat model of diabetic wounds. The DDM scaffolds were prepared from harvested human skin samples and histological, ultrastructural, molecular and mechanical assessments were carried out. In comparison with the control (without any treatment) and DDM alone group, full thickness excisional wounds treated with HUCPVCs-loaded DDM scaffolds demonstrated an accelerated wound closure rate, faster re-epithelization, more granulation tissue formation and decreased collagen deposition. Furthermore, immunofluorescence analysis showed that the VEGFR-2 expression and vascular density in the HUCPVCs-loaded DDM scaffold treated group were also significantly higher than the other groups at 7days post implantation. Since the rates of angiogenesis, re-epithelization and formation of granulation tissue are directly correlated with full thickness wound healing in patients, the proposed HUCPVCs-loaded DDM scaffolds may fulfil a role neglected by current treatment strategies. This pre-clinical proof-of-concept study warrants further clinical evaluation. STATEMENT OF SIGNIFICANCE: The aim of the present study was to design a novel tissue-engineered system to promote angiogenesis, re-epithelization and granulation of skin tissue using human umbilical cord perivascular stem cells and decellularized dermal matrix natural scaffolds in rat diabetic wound models. The authors of this research article have been working on stem cells and tissue engineering scaffolds for years. According to our knowledge, there is a lack of an efficient system for the treatment of skin defects using tissue engineering strategy. Since the rates of angiogenesis, re-epithelization and granulation tissue are directly correlated with full thickness wound healing, the proposed HUCPVCs-loaded DDM scaffolds perfectly fills the niche neglected by current treatment strategies. This pre-clinical study demonstrates the proof-of-concept that necessitates clinical evaluations.

Anemia Outcome After Laparascopic Mini Bypass : Analysis of 107 Consecutive Patients.

BACKGROUND: The prevalence of obesity has dramatically increased globally. Weight loss procedures are known to be an effective and reliable method with relatively low complication rate and satisfactory results. Laparoscopic mini-gastric bypass (LMGB) is known as a modified Mason loop procedure with compatible results to laparoscopic Roux-en-Y gastric bypass (LRYGB), and is believed to have even less complication rate. Despite adequate and meticulous supplement therapy, anemia is one of the challenges in patients undergoing LMGB. Thus, we aimed to review the prevalence and severity of anemia in patients undergoing LMGB. METHOD: A prospectively-maintained database of patients referring to Hazrat Rasoul Akram hospital who underwent LMGB from December 2013 to October 2014 was reviewed retrospectively. RESULTS: A total of 113 consecutive patients were included in the study. The mean age was 38.7 ±â€ˆ9.8 years. Mean Body mass index (BMI) was 45.5 ±â€ˆ6.1 kg/m2 preoperatively and 36.7 ±â€ˆ5.5 kg/m2 and 33.0 ±â€ˆ5.3 kg/m2 three and six months after the procedure, respectively. (P = 0.001) Mean excess body weight loss after the procedure was 20% and 53% at three and six months post operatively. Serum hemoglobin (Hb) level decreased significantly in three months (P = 0.036) and remained unchanged in six months compared to 3-month (P = 0.385). Vitamin B12 level increased significantly in three months (P = 0.010) and then decrease in six months to the preoperative level (P = 0.889). CONCLUSION: LMGB is a safe, feasible and an effective alternative weight loss procedure. Simply, anemia can be prevented by utilizing therapeutic dose of multivitamin in patients who underwent this procedure.