Semiparametric estimation of the transformation model by leveraging external aggregate data in the presence of population heterogeneity.

Leveraging information in aggregate data from external sources to improve estimation efficiency and prediction accuracy with smaller scale studies has drawn a great deal of attention in recent years. Yet, conventional methods often either ignore uncertainty in the external information or fail to account for the heterogeneity between internal and external studies. This article proposes an empirical likelihood-based framework to improve the estimation of the semiparametric transformation models by incorporating information about the t-year subgroup survival probability from external sources. The proposed estimation procedure incorporates an additional likelihood component to account for uncertainty in the external information and employs a density ratio model to characterize population heterogeneity. We establish the consistency and asymptotic normality of the proposed estimator and show that it is more efficient than the conventional pseudopartial likelihood estimator without combining information. Simulation studies show that the proposed estimator yields little bias and outperforms the conventional approach even in the presence of information uncertainty and heterogeneity. The proposed methodologies are illustrated with an analysis of a pancreatic cancer study.

Isolation and Quantification of Methylated Cell-Free DNA in Plasma on an Integrated Microfluidic System.

Methylated cell-free DNA (cfDNA) has been deemed a promising biomarker for ovarian cancer (OvCa) prognosis and therapy selection. However, exploring the methylation profiles of tumor suppressor genes in cfDNA remains a challenge due to their extremely low concentrations and complicated protocols, as well as methodological constraints. In this study, an integrated microfluidic system was developed to automatically (1) capture methylated cfDNA in plasma by magnetic beads coated with the methyl-CpG-binding domain and (2) quantify the methylation level of tumor suppressor genes by on-chip quantitative polymerase chain reaction (qPCR). For capturing methylated cfDNA from a very small amount of plasma, samples along with beads were mixed in a new micromixer to enhance the capture rate. With a high capture rate (72%) and a limit of quantification of 0.1 pg/µL (3 orders of magnitude lower than that of the benchtop method), the compact system could detect the methylated cfDNA from only 20 µL of plasma sample in 2 h. Furthermore, the dynamic range, from 0.1 to 2000 pg/µL of methylated cfDNA, spans the physiological range in plasma, signifying that this device has great potential for personalized medicine in OvCa.

Estimations of the joint distribution of failure time and failure type with dependent truncation.

In biomedical studies involving survival data, the observation of failure times is sometimes accompanied by a variable which describes the type of failure event (Kalbeisch and Prentice, 2002). This paper considers two specific challenges which are encountered in the joint analysis of failure time and failure type. First, because the observation of failure times is subject to left truncation, the sampling bias extends to the failure type which is associated with the failure time. An analytical challenge is to deal with such sampling bias. Second, in case that the joint distribution of failure time and failure type is allowed to have a temporal trend, it is of interest to estimate the joint distribution of failure time and failure type nonparametrically. This paper develops statistical approaches to address these two analytical challenges on the basis of prevalent survival data. The proposed approaches are examined through simulation studies and illustrated by using a real data set.

Methods for multivariate recurrent event data with measurement error and informative censoring.

In multivariate recurrent event data regression, observation of recurrent events is usually terminated by other events that are associated with the recurrent event processes, resulting in informative censoring. Additionally, some covariates could be measured with errors. In some applications, an instrumental variable is observed in a subsample, namely a calibration sample, which can be applied for bias correction. In this article, we develop two non-parametric correction approaches to simultaneously correct for the informative censoring and measurement errors in the analysis of multivariate recurrent event data. A shared frailty model is adopted to characterize the informative censoring and dependence among different types of recurrent events. To adjust for measurement errors, a non-parametric correction method using the calibration sample only is proposed. In the second approach, the information from the whole cohort is incorporated by the generalized method of moments. The proposed methods do not require the Poisson-type assumption for the multivariate recurrent event process and the distributional assumption for the frailty. Moreover, we do not need to impose any distributional assumption on the underlying covariates and measurement error. Both methods perform well, but the second approach improves efficiency. The proposed methods are applied to the Nutritional Prevention of Cancer trial to assess the effect of selenium treatment on the recurrences of basal cell carcinoma and squamous cell carcinoma.

Lidocaine Skin Patch (Lidopat® 5%) Is Effective in the Treatment of Traumatic Rib Fractures: A Prospective Double-Blinded and Vehicle-Controlled Study.

OBJECTIVE: The purpose of this study was to determine the efficacy of the Lidopat(®) 5% skin patch in relieving rib fracture pain. SUBJECTS AND METHODS: From June 2009 to May 2011, 44 trauma patients with isolated rib fractures were enrolled in this study and randomized in a double-blind method into 2 groups. The experimental group (group E: 27 patients) used a Lidopat(®) 5% skin patch at the trauma site and took an oral analgesic drug for pain relief. The placebo group (group P: 17 patients) used a placebo vehicle patch and an oral analgesic drug. RESULTS: The mean age, weight and hospital stay of patients were 56.8 ± 13.8 years, 67.4 ± 12.6 kg and 6.34 ± 1.3 days, respectively. In the first 4 days, there were no significant differences in pain scores between the groups (p > 0.05). After the 5th day, the average pain score was significantly less in group E (mean 1.5) than in group P (mean 3.10; p < 0.05). There was no significant difference in the number of fractured ribs between groups (p = 0.904). The use of meperidine and the length of hospital stay (6.0 vs. 6.9 days) were both significantly less in group E (p = 0.043 and 0.009, respectively). CONCLUSION: In this study, the use of the Lidopat(®) 5% skin patch in patients with isolated rib fractures alleviated pain and shortened the hospital stay, and a lower dose of pain-relieving medication was used.

Causal estimation using semiparametric transformation models under prevalent sampling.

This article presents methods and inference for causal estimation in semiparametric transformation models for the prevalent survival data. Through the estimation of the transformation models and covariate distribution, we propose a few analytical procedures to estimate the causal survival function. As the data are observational, the unobserved potential outcome (survival time) may be associated with the treatment assignment, and therefore there may exist a systematic imbalance between the data observed from each treatment arm. Further, due to prevalent sampling, subjects are observed only if they have not experienced the failure event when data collection began, causing the prevalent sampling bias. We propose a unified approach, which simultaneously corrects the bias from the prevalent sampling and balances the systematic differences from the observational data. We illustrate in the simulation study that standard analysis without proper adjustment would result in biased causal inference. Large sample properties of the proposed estimation procedures are established by techniques of empirical processes and examined by simulation studies. The proposed methods are applied to the Surveillance, Epidemiology, and End Results (SEER) and Medicare-linked data for women diagnosed with breast cancer.

Combined estimating equation approaches for semiparametric transformation models with length-biased survival data.

Survival data are subject to length-biased sampling when the survival times are left-truncated and the underlying truncation time random variable is uniformly distributed. Substantial efficiency gains can be achieved by incorporating the information about the truncation time distribution in the estimation procedure [Wang (1989) Journal of the American Statistical Association 84, 742-748; Wang (1996) Biometrika 83, 343-354]. Under the semiparametric transformation models, the maximum likelihood method is expected to be fully efficient, yet it is difficult to implement because the full likelihood depends on the nonparametric component in a complicated way. Moreover, its asymptotic properties have not been established. In this article, we extend the martingale estimating equation approach [Chen et al. (2002) Biometrika 89, 659-668; Kim et al. (2013) Journal of the American Statistical Association 108, 217-227] and the pseudo-partial likelihood approach [Severini and Wong (1992) The Annals of Statistics 4, 1768-1802; Zucker (2005) Journal of the American Statistical Association 100, 1264-1277] for semiparametric transformation models with right-censored data to handle left-truncated and right-censored data. In the same spirit of the composite likelihood method [Huang and Qin (2012) Journal of the American Statistical Association 107, 946-957], we further construct another set of unbiased estimating equations by exploiting the special probability structure of length-biased sampling. Thus the number of estimating equations exceeds the number of parameters, and efficiency gains can be achieved by solving a simple combination of these estimating equations. The proposed methods are easy to implement as they do not require additional programming efforts. Moreover, they are shown to be consistent and asymptotically normally distributed. A data analysis of a dementia study illustrates the methods.

Methylation status of retinoic acid receptor beta2 promoter and global DNA in esophageal squamous cell carcinoma.

BACKGROUND: Focal hypermethylation in promoter regions of tumor suppressor genes against the background of global hypomethylation is a landmark of carcinogenesis. This study aimed to investigate the methylation status of retinoic acid receptor beta2 (RARß2) and long interspersed nuclear elements (LINE-1) in different stages of esophageal squamous cell carcinoma (ESCC). METHOD: The tumor and adjacent normal esophageal tissues from 125 male ESCC patients who underwent primary surgery were analyzed for the methylation status of RARß2 promoter and LINE-1 through methylation-specific polymerase chain reaction and pyrosequencing. RESULTS: RARß2 hypermethylation was detected in 20% of the tumor samples, but not in the normal counterparts. The methylation frequency of LINE-1 was significantly lower in the tumor than in the normal parts (median: 67.7% vs. 80%, P < 0.0005). Ninety-eight patients (78.4%) had both RARß2 hypermethylation and LINE-1 hypomethylation or either one. There was a trend toward higher risk of advanced T stage (P for trend = 0.05) or lymph node metastasis (P for trend = 0.02) when more adverse gene methylation profiles were present. CONCLUSION: Methylation status of RARß2 and LINE-1 was related to the development and possibly the severity of ESCC.

Antituberculosis treatment and hepatotoxicity in patients with chronic viral hepatitis.

BACKGROUND: Whether antituberculosis (anti-TB) treatment in patients with chronic viral hepatitis affects the incidence and onset time of drug-induced hepatotoxicity (DIH) is still controversial. The aim of this retrospective study was to find out whether chronic viral hepatitis affects the incidence and onset time of DIH. METHODS: All patients diagnosed with active TB and being treated at a tertiary referral hospital between 2002 and 2009 were identified from medical records, from which 553 patients were enrolled in the study. The incidence and onset of DIH in patients with and without chronic viral hepatitis (controls) were compared. RESULTS: The incidence of DIH was similar in patients with and without chronic hepatitis (8 % [32/392] vs. 7 % [11/161], P > 0.05). The incidence of transient liver function impairment (TLI) was significantly lower in controls than in chronic hepatitis patients (2 % [9/392] vs. 12 % [20/161], P < 0.001. The mean onset times of DIH in the control, hepatitis B virus (HBV), and hepatitis C virus (HCV) groups were not significantly different (40, 39, and 67 days, respectively, all P > 0.05). The mean onset times of TLI in the control, HBV, and HCV groups were significantly different (23, 48, and 68 days, respectively, all P < 0.05). CONCLUSIONS: Liver function impairment during anti-TB therapy in patients with chronic viral hepatitis was due to mostly TLI, with TLI occurring later than in controls. Chronic viral hepatitis had no significant effect on the incidence of DIH.

Lc3 over-expression improves survival and attenuates lung injury through increasing autophagosomal clearance in septic mice.

OBJECTIVE: To clarify the role of autophagy in sepsis-induced lung injury. BACKGROUND: The role of autophagy as a protective or maladaptive response in lung cells during sepsis has not yet been determined. The lack of specificity of the autophagic process has driven the development of new approaches that assess autophagosomes from formation to fusion with lysosomes. METHODS: Sepsis was induced by cecal ligation and puncture (CLP). The autophagic process was manipulated using the pharmacological inhibitors of the autophagy pathway. Green fluorescent protein (GFP)-microtubule-associated protein 1 light chain 3 (LC3) transgenic mice were further used to determine the role of autophagy. RESULTS: The formation of autophagosomal protein LC3-II progressively accumulated in the lungs over 24 hours after CLP, with the Lc3 gene expression returning to baseline levels at 24 hours. Autophagosome-lysosome fusion, however, gradually decreased from 8 to 24 hours after CLP, suggesting impaired clearance of autophagosomes rather than upregulation of autophagy in the septic lung. In contrast, transgenic mice overexpressing the Lc3 gene exhibited increased clearance of autophagosomes and improved survival after CLP. This protective effect was also seen in decreased cell death, inflammatory responses, neutrophil accumulation, albumin leakage, and edema formation. However, blockade of autophagosome-lysosome fusion with bafilomycin A1 abolished the protective effects in transgenic mice. This indicates that Lc3 transgene attenuates lung injury/inflammation in sepsis, possibly through increasing the clearance of autophagosomes. CONCLUSIONS: Autophagy in the septic lung represents a protective response. However, autophagy, by virtue of excessive autophagosome accumulation, may play a maladaptive role in the late stage of sepsis, leading to acute lung injury.

The synthetic flavonoid WYC02-9 inhibits cervical cancer cell migration/invasion and angiogenesis via MAPK14 signaling.

OBJECTIVE: Development of flavonoids as potential chemotherapeutic agents for cervical cancer may open new avenues in anticancer drug design. In this study, the cytotoxic activity and anti-migration/invasion/angiogenesis efficiency of the synthetic flavonoid WYC02-9 on cervical cancer and the underlying mechanisms are explored. METHODS: XTT cell viability assay, apoptosis assays, cell cycle analysis, and immunoblotting analysis were applied to study the biologic activity of WYC02-9. Anchorage independent soft agar assay and xenograft nude mouse model were applied to study the anti-tumor effect of WYC02-9 in vivo. Wound healing assay, transwell invasion assay, and gelatin zymography analysis were applied to study the effect of WYC02-9 on cancer cell migration and invasion. Tube formation analysis, zebrafish angiogenesis model, and nude mice Matrigel plug angiogenesis assay were applied to study the effect of WYC02-9 on angiogenesis. RESULTS: WYC02-9 induced cytotoxicity on cervical cancer cells by promoting apoptosis and G2/M cell cycle arrest. WYC02-9 inhibited cervical cancer cell migration/invasion and angiogenesis in vitro and in vivo via MAPK14 pathway. CONCLUSION: WYC02-9 significantly inhibited cervical cancer cell proliferation/migration/invasion and angiogenesis in vitro and in vivo. WYC02-9 may be a promising drug candidate for cervical cancer chemotherapy.

Zoonotic atypical pneumonia due to Chlamydophila psittaci: first reported psittacosis case in Taiwan.

Human psittacosis caused by Chlamydophila psittaci is one of the most common zoonotic atypical pneumonias featuring pulmonary as well as extrapulmonary infections. Most of the cases involve avian contact history especially with psittacine birds. Herein we report a 44-year-old male patient displaying atypical pneumonia symptoms of intermittent fever, dry cough, chest pain, dyspnea, headache, hepatitis, and hyponatremia. He had two sick cockatiels, one of which had died a month previously. A microimmunofluorescence test was performed to check the serum antibody levels against Chlamydophila psittaci. The serum IgM titer showed positive titer of 1:256, 1:256, and 1:128 on Days 11, 23, and 43 after disease onset, respectively. His fever subsided soon and clinical symptoms improved after minocycline was administrated on Day 12. The psittacosis case was confirmed by history of psittacine bird contact, clinical symptoms, treatment response, and positive IgM titer. To our knowledge, this is the first report of a psittacosis case in Taiwan.

Agreement assessment of tigecycline susceptibilities determined by the disk diffusion and broth microdilution methods among commonly encountered resistant bacterial isolates: results from the Tigecycline In Vitro Surveillance in Taiwan (TIST) study, 2008 to 2010.

The Tigecycline In Vitro Surveillance in Taiwan (TIST) study, initiated in 2006, is a nationwide surveillance program designed to longitudinally monitor the in vitro activity of tigecycline against commonly encountered drug-resistant bacteria. This study compared the in vitro activity of tigecycline against 3,014 isolates of clinically important drug-resistant bacteria using the standard broth microdilution and disk diffusion methods. Species studied included methicillin-resistant Staphylococcus aureus (MRSA; n = 759), vancomycin-resistant Enterococcus faecium (VRE; n = 191), extended-spectrum ß-lactamase (ESBL)-producing Escherichia coli (n = 602), ESBL-producing Klebsiella pneumoniae (n = 736), and Acinetobacter baumannii (n = 726) that had been collected from patients treated between 2008 and 2010 at 20 hospitals in Taiwan. MICs and inhibition zone diameters were interpreted according to the currently recommended U.S. Food and Drug Administration (FDA) criteria and the European Committee on Antimicrobial Susceptibility Testing (EUCAST) criteria. The MIC(90) values of tigecycline against MRSA, VRE, ESBL-producing E. coli, ESBL-producing K. pneumoniae, and A. baumannii were 0.5, 0.125, 0.5, 2, and 8 µg/ml, respectively. The total error rates between the two methods using the FDA criteria were high: 38.4% for ESBL-producing K. pneumoniae and 33.8% for A. baumannii. Using the EUCAST criteria, the total error rate was also high (54.6%) for A. baumannii isolates. The total error rates between these two methods were <5% for MRSA, VRE, and ESBL-producing E. coli. For routine susceptibility testing of ESBL-producing K. pneumoniae and A. baumannii against tigecycline, the broth microdilution method should be used because of the poor correlation of results between these two methods.

Trends in susceptibility of vancomycin-resistant Enterococcus faecium to tigecycline, daptomycin, and linezolid and molecular epidemiology of the isolates: results from the Tigecycline In Vitro Surveillance in Taiwan (TIST) study, 2006 to 2010.

Among the 219 vancomycin-resistant Enterococcus faecium isolates collected in 20 Taiwanese hospitals from 2006 to 2010, all were susceptible to linezolid and daptomycin, and 98.6% were susceptible to tigecycline. There was a shift toward higher tigecycline MIC values (MIC(90)s) from 2006-2007 (0.06 µg/ml) to 2008-2010 (0.12 µg/ml). The MIC(90)s of daptomycin and linezolid remained stationary. Although pulsotypes among the isolates from the 20 hospitals varied, intrahospital spreading of several clones was identified in 13 hospitals.

Trends in the susceptibility of clinically important resistant bacteria to tigecycline: results from the Tigecycline In Vitro Surveillance in Taiwan study, 2006 to 2010.

The Tigecycline In Vitro Surveillance in Taiwan (TIST) study, a nationwide, prospective surveillance during 2006 to 2010, collected a total of 7,793 clinical isolates, including methicillin-resistant Staphylococcus aureus (MRSA) (n = 1,834), penicillin-resistant Streptococcus pneumoniae (PRSP) (n = 423), vancomycin-resistant enterococci (VRE) (n = 219), extended-spectrum ß-lactamase (ESBL)-producing Escherichia coli (n = 1,141), ESBL-producing Klebsiella pneumoniae (n = 1,330), Acinetobacter baumannii (n = 1,645), and Stenotrophomonas maltophilia (n = 903), from different specimens from 20 different hospitals in Taiwan. MICs of tigecycline were determined following the criteria of the U.S. Food and Drug Administration (FDA) and the European Committee on Antimicrobial Susceptibility Testing (EUCAST-2011). Among drug-resistant Gram-positive pathogens, all of the PRSP isolates were susceptible to tigecycline (MIC(90), 0.03 µg/ml), and only one MRSA isolate (MIC(90), 0.5 µg/ml) and three VRE isolates (MIC(90), 0.125 µg/ml) were nonsusceptible to tigecycline. Among the Gram-negative bacteria, the tigecycline susceptibility rates were 99.65% for ESBL-producing E. coli (MIC(90), 0.5 µg/ml) and 96.32% for ESBL-producing K. pneumoniae (MIC(90), 2 µg/ml) when interpreted by FDA criteria but were 98.7% and 85.8%, respectively, when interpreted by EUCAST-2011 criteria. The susceptibility rate for A. baumannii (MIC(90), 4 µg/ml) decreased from 80.9% in 2006 to 55.3% in 2009 but increased to 73.4% in 2010. A bimodal MIC distribution was found among carbapenem-susceptible A. baumannii isolates, and a unimodal MIC distribution was found among carbapenem-nonsusceptible A. baumannii isolates. In Taiwan, tigecycline continues to have excellent in vitro activity against several major clinically important drug-resistant bacteria, with the exception of A. baumannii.

Estimating propensity scores and causal survival functions using prevalent survival data.

This article develops semiparametric approaches for estimation of propensity scores and causal survival functions from prevalent survival data. The analytical problem arises when the prevalent sampling is adopted for collecting failure times and, as a result, the covariates are incompletely observed due to their association with failure time. The proposed procedure for estimating propensity scores shares interesting features similar to the likelihood formulation in case-control study, but in our case it requires additional consideration in the intercept term. The result shows that the corrected propensity scores in logistic regression setting can be obtained through standard estimation procedure with specific adjustments on the intercept term. For causal estimation, two different types of missing sources are encountered in our model: one can be explained by potential outcome framework; the other is caused by the prevalent sampling scheme. Statistical analysis without adjusting bias from both sources of missingness will lead to biased results in causal inference. The proposed methods were partly motivated by and applied to the Surveillance, Epidemiology, and End Results (SEER)-Medicare linked data for women diagnosed with breast cancer.

Monoamine oxidase A regulates antisocial personality in whites with no history of physical abuse.

OBJECTIVE: Preclinical and human family studies clearly link monoamine oxidase A (MAOA) to aggression and antisocial personality (ASP). The 30-base pair variable number tandem repeat in the MAOA promoter regulates MAOA levels, but its effects on ASP in humans are unclear. METHODS: We evaluated the association of the variable number tandem repeat of the MAOA promoter with Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, ASP disorder (ASPD) traits in a community sample of 435 participants from the Hopkins Epidemiology of Personality Disorders Study. RESULTS: We did not find an association between the activity of the MAOA allele and ASPD traits; however, among whites, when subjects with a history of childhood physical abuse were excluded, the remaining subjects with low-activity alleles had ASPD trait counts that were 41% greater than those with high-activity alleles (P < .05). CONCLUSION: The high-activity MAOA allele is protective against ASP among whites with no history of physical abuse, lending support to a link between MAOA expression and antisocial behavior.

Associations between emotional intelligence and doctor burnout, job satisfaction and patient satisfaction.

CONTEXT: The occupational health literature has long been dominated by stress-related topics. A more contemporary perspective suggests using a positive approach in the form of a health model focused on what is right with people, such as feelings of well-being and satisfaction. OBJECTIVES: Using a positive perspective and multi-source data collection, this study investigated the inter-relationships among emotional intelligence (EI), patient satisfaction, doctor burnout and job satisfaction. METHODS: In this observational study, 110 internists and 2872 out-patients were surveyed in face-to-face interviews. RESULTS: Higher self-rated EI was significantly associated with less burnout (p<0.001) and higher job satisfaction (p<0.001). Higher patient satisfaction was correlated with less burnout (p<0.01). Less burnout was found to be associated with higher job satisfaction (p<0.001). CONCLUSIONS: This study identified EI as a factor in understanding doctors' work-related issues. Given the multi-dimensional nature of EI, refinement of the definition of EI and the construct validity of EI as rated by others require further examination.

High-mobility group box 1-mediated matrix metalloproteinase-9 expression in non-small cell lung cancer contributes to tumor cell invasiveness.

High-mobility group box 1 (HMGB1) is a versatile protein with intranuclear and extracellular functions. It is involved in invasion and metastasis in various human malignancies. However, the role of HMGB1 in non-small cell lung cancer (NSCLC) is unclear. We hypothesized that HMGB1 expression is a determinant of cellular invasiveness and metastasis in lung cancer. We examined HMGB1 expression in 48 NSCLC specimens by quantitative real-time PCR. High HMGB1 expression was significantly associated with clinically advanced stages (stage III-IV) (P < 0.05) and was correlated to expression of matrix metalloproteinase-9 (MMP-9) (P < 0.05). Patients with high levels of HMGB1 expression had poorer clinical prognosis. The expression level of MMP-9 and metastatic ability in vitro were significantly higher in an HMGB1-overexpressing human NSCLC cell lines (A549 and H23). The treatment with HMGB1 small interfering RNA reduced MMP-9 expression and the cellular metastatic ability in NSCLC cells. We also demonstrated that phosphoinositide 3-kinase/Akt and NF-κB-related pathways contributed to the HMGB1-induced MMP-9 expression and cellular metastatic ability.