Event History Analysis in Longitudinal Cohort Studies with Intermittent Inspection Times

Event history studies based on disease clinic data often face several complications. Specifically, patients visit the clinic irregularly, and the intermittent inspection times depend on the history of disease-related variables; this can cause event or failure times to be dependently interval-censored. Furthermore, failure times could be truncated, treatment assignment is non-randomized and can be confounded, and there are competing risks of the failure time outcomes under study. I propose a class of inverse probability weights applied to estimating functions so that the informative inspection scheme and confounded treatment are appropriately dealt with. As a result, the distribution of failure time outcomes can be consistently estimated. I consider parametric, non- and semi-parametric estimation. Monotone smoothing techniques are employed in a two-stage estimation procedure for the non- or semi-parametric estimation. Simulations for a variety of failure time models are conducted for examining the finite sample performances of proposed estimators. This research is initially motivated by the Psoriatic Arthritis (PsA) Toronto Cohort Study at the Toronto Western Hospital and the proposed methodologies are applied to this cohort study as an illustration

Minimum hellinger distance estimation for a two-sample semiparametric cure rate model with censored survival data

Bibliography: p. 74-77

High Density Culture Process and Growth Kinetics of Flavor Yeast A10-2

In order to realize the high-density culture and establish the predictive growth kinetics model of a self-isolated flavor yeast, the high-density culture process was studied of 4-ethyl-2-methoxyphenol producing yeast A10-2, which screened from soy sauce fermentation mash. The type of culture medium (nitrogen and carbon source) and concentration were studied and optimized. The growth kinetics and the substrate (total sugar) consumption models were established and verified. The results showed that (NH4) H2PO4 fed to make the concentration of culture medium 0.2 g/100 mL was the best inorganic source of nitrogen. To obtain the best cell growth rate, molasses as the only source of carbon, should be fed which controlled the concentration of total sugar in the culture medium to 0.4~0.6 g/100 mL. The growth of A10-2 yeast followed the S-shaped curve of a Logistic model, and the substrate (total sugar) consumption followed the Leudeking-Priet equation. The maximum obtained biomass specific growth rate μm was 0.4764 h−1, while the maximum biomass growth yield coefficient YG was 0.5879 g/g. The maintenance coefficient was 0.0127 g·L−1·h−1. The established models could better describe the growth and sugar consumption of yeast in the process of high-density culture, and have predictive significance

Microporous Mesoporous Mat.

A simple route has been developed to synthesize mesoporous CuO-CeO2 mixed oxides. X-ray diffraction, N-2 adsorption and desorption isotherms, and high-resolution transmission electron microscopy have been used to characterize the obtained mesoporous CuOCeO2 mixed oxides. The results revealed that the as-prepared CuO-CeO2 mixed oxides possessed a high BET surface area and pores in the range of 1-10 nm after calcination at 600 degrees C for 4 h. In order to understand the formation mechanism of the mesoporous structure, the precursor before calcination was characterized by FTIR and TG-DSC. The results showed that the formation of the mesoporous structure with the high BET surface area was ascribed to the decomposition of ammonia nitrate. Further experimental investigations revealed that the amount of ammonia nitrate in the precursor greatly influenced the BET surface area and the pore size of the final product. Furthermore, the method could be extended to the synthesis of other mixed oxides with the mesoporous structures, such as ZrO2CeO2 and ZrO2-Y2O3. The as-prepared mesoporous CuO-CeO2 sample with the high surface area exhibited highly reducible features as compared to the sample with a low surface area. The mesoporous CuO-CeO2 powder showed excellent catalytic activity for the complete oxidation of benzene. (C) 2007 Elsevier Inc. All rights reserved.A simple route has been developed to synthesize mesoporous CuO-CeO2 mixed oxides. X-ray diffraction, N-2 adsorption and desorption isotherms, and high-resolution transmission electron microscopy have been used to characterize the obtained mesoporous CuOCeO2 mixed oxides. The results revealed that the as-prepared CuO-CeO2 mixed oxides possessed a high BET surface area and pores in the range of 1-10 nm after calcination at 600 degrees C for 4 h. In order to understand the formation mechanism of the mesoporous structure, the precursor before calcination was characterized by FTIR and TG-DSC. The results showed that the formation of the mesoporous structure with the high BET surface area was ascribed to the decomposition of ammonia nitrate. Further experimental investigations revealed that the amount of ammonia nitrate in the precursor greatly influenced the BET surface area and the pore size of the final product. Furthermore, the method could be extended to the synthesis of other mixed oxides with the mesoporous structures, such as ZrO2CeO2 and ZrO2-Y2O3. The as-prepared mesoporous CuO-CeO2 sample with the high surface area exhibited highly reducible features as compared to the sample with a low surface area. The mesoporous CuO-CeO2 powder showed excellent catalytic activity for the complete oxidation of benzene. (C) 2007 Elsevier Inc. All rights reserved

Dataset for: Estimation of parametric failure time distributions based on interval-censored data with irregular dependent follow-up

Event history studies based on disease clinic data often face several complications. Specifically, patients may visit the clinic irregularly, and the intermittent observation times could depend on disease-related variables; this can cause a failure time outcome to be dependently interval-censored. We propose a weighted estimating function approach so that dependently interval-censored failure times can be analysed consistently. A so-called inverse-intensity-of-visit (IIV) weight is employed to adjust for the informative inspection times. Left truncation of failure times can also be easily handled. Additionally, in observational studies, treatment assignments are typically non-randomized, and may depend on disease-related variables. An inverse-probability-of-treatment (IPT) weight is applied to estimating functions to further adjust for measured confounders. Simulation studies are conducted to examine the finite sample performances of the proposed estimators. Finally, the Toronto Psoriatic Arthritis (PsA) Cohort Study is used for illustration

Meta-Analysis of Long-Term Vitamin D Supplementation on Overall Mortality

<div><p>Introduction</p><p>It has been suggested that vitamin D is effective to prevent mortality. However, there is no consistent conclusion that the effects of vitamin D supplementation on all-cause mortality are associated with duration of treatment. We conducted a meta-analysis regarding this issue in an effort to provide a more robust answer.</p> <p>Methods</p><p>A comprehensive search in a number of databases, including MEDLINE, Embase and The Cochrane Central Register of Controlled Trials, was conducted for collecting randomized controlled trials (RCTs) on vitamin D supplementation preventing mortality. Two investigators independently screened the literature according to the inclusive and exclusive criteria and the relative data were extracted. Data analysis was performed by using Review Manager 5.0 software.</p> <p>Results</p><p>Data from forty-two RCT s were included. Vitamin D therapy significantly decreased all-cause mortality with a duration of follow-up longer than 3 years with a RR (95% CI) of 0.94 (0.90–0.98). No benefit was seen in a shorter follow-up periods with a RR (95% CI) of 1.04 (0.97–1.12). Results remain robust after sensitivity analysis. The following subgroups of long-term follow-up had significantly fewer deaths: female only, participants with a mean age younger than 80, daily dose of 800 IU or less, participants with vitamin D insufficiency (baseline 25-hydroxyvitamin D level less than 50 nmol/L) and cholecalciferol therapy. In addition, the combination of vitamin D and calcium significantly reduced mortality and vitamin D alone also had a trend to decrease mortality in a longer time follow up.</p> <p>Conclusions</p><p>The data suggest that supplementation of vitamin D is effective in preventing overall mortality in a long-term treatment, whereas it is not significantly effective in a treatment duration shorter than 3 years. Future studies are needed to identify the efficacy of vitamin D on specific mortality, such as cancer and cardiovascular disease mortality in a long-term treatment duration.</p> </div

An Updated Meta-Analysis of Fatal Adverse Events Caused by Bevacizumab Therapy in Cancer Patients

<div><p>Background</p><p>The risk of fatal adverse events (FAEs) due to bevacizumab-based chemotherapy has not been well described; we carried out an updated meta-analysis regarding this issue.</p><p>Methods</p><p>An electronic search of Medline, Embase and The Cochrane Central Register of Controlled Trials was conducted to investigate the effects of randomized controlled trials on bevacizumab treatment on cancer patients. Random or fixed-effect meta-analytical models were used to evaluate the risk ratio (RR) of FAEs due to the use of bevacizumab.</p><p>Results</p><p>Thirty-four trials were included. Allocation to bevacizumab therapy significantly increased the risk of FAEs; the RR was 1.29 (95% CI:1.05–1.57). This association varied significantly with tumor types (<i>P</i> = 0.002) and chemotherapeutic agents (<i>P</i> = 0.005) but not with bevacizumab dose (<i>P</i> = 0.90). Increased risk was seen in patients with non–small cell lung cancer, pancreatic cancer, prostate cancer, and ovarian cancer. However, FAEs were lower in breast cancer patients treated with bevacizumab. In addition, bevacizumab was associated with an increased risk of FAEs in patients who received concomitant agents of taxanes and/or platinum.</p><p>Conclusion</p><p>Compared with chemotherapy alone, the addition of bevacizumab was associated with an increased risk of FAEs among patients with special tumor types, particularly when combined with chemotherapeutic agents such as platinum.</p></div

Risk ratio of fatal adverse events by subgroup.

<p>NSCLC, non– small cell lung cancer; SCLC, small cell lung cancer; RR, risk ratio; PFS, progression-free survival; NA, not applicable.</p