Econometrics Commons^™

Cities In A Pandemic: Evidence From China, Badi H. Baltagi, Ying Deng, Li Jing, Zhenlin Yang

Research Collection School Of Economics

This paper studies the impact of urban density, city government efficiency, and medical resources on COVID-19 infection and death outcomes in China. We adopt a simultaneous spatial dynamic panel data model to account for (i) the simultaneity of infection and death outcomes, (ii) the spatial pattern of the transmission, (iii) the intertemporal dynamics of the disease, and (iv) the unobserved city-specific and time-specific effects. We find that, while population density increases the level of infections, government efficiency significantly mitigates the negative impact of urban density. We also find that the availability of medical resources improves public health outcomes conditional on …

Change In Outbreak Epicentre And Its Impact On The Importation Risks Of Covid-19 Progression: A Modelling Study, Oyelola A. Adegboye, Adeshina I. Adekunle, Anton Pak, Ezra Gayawan, Denis H. Y. Leung, Diana P. Rojas, Emma S. Mcbryde, Damon P. Eisen

Research Collection School Of Economics

Background: The outbreak of Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) that was first detected in the city of Wuhan, China has now spread to every inhabitable continent, but now the attention has shifted from China to other epicentres. This study explored early assessment of the influence of spatial proximities and travel patterns from Italy on the further spread of SARS-CoV-2 worldwide. Methods: Using data on the number of confirmed cases of COVID-19 and air travel data between countries, we applied a stochastic meta-population model to estimate the global spread of COVID-19. Pearson's correlation, semi-variogram, and Moran's Index were used to …

Activation Of Trpa1 Nociceptor Promotes Systemic Adult Mammalian Skin Regeneration, Jenny J. Wei, Hali S. Kim, Casey A. Spencer, Donna Brennan-Crispi, Ying Zheng, Nicolette M. Johnson, Misha Rosenbach, Christopher Miller, Denis H. Y. Leung, George Cotsarelis, Thomas H. Leung

Research Collection School Of Economics

Adult mammalian wounds, with rare exception, heal with fibrotic scars that severely disrupt tissue architecture and function. Regenerative medicine seeks methods to avoid scar formation and restore the original tissue structures. We show in three adult mouse models that pharmacologic activation of the nociceptor TRPA1 on cutaneous sensory neurons reduces scar formation and can also promote tissue regeneration. Local activation of TRPA1 induces tissue regeneration on distant untreated areas of injury, demonstrating a systemic effect. Activated TRPA1 stimulates local production of interleukin-23 (IL-23) by dermal dendritic cells, leading to activation of circulating dermal IL-17–producing γδ T cells. Genetic ablation of …

Aging Suppresses Skin-Derived Circulating Sdf1 To Promote Full-Thickness Tissue Regeneration, Mailyn A. Nishiguchi, Casey A. Spencer, Denis H. Y. Leung, Thomas H. Leung

Research Collection School Of Economics

Physicians have observed that surgical wounds in the elderly heal with thinner scars than wounds in young patients. Understanding this phenomenon may reveal strategies for promoting scarless wound repair. We show that full-thickness skin wounds in aged but not young mice fully regenerate. Exposure of aged animals to blood from young mice by parabiosis counteracts this regenerative capacity. The secreted factor, stromal-derived factor 1 (SDF1), is expressed at higher levels in wounded skin of young mice. Genetic deletion of SDF1 in young skin enhanced tissue regeneration. In aged mice, enhancer of zeste homolog 2 (EZH2) and histone H3 lysine 27 …

Joint Spatial Time Series Epidemiological Analysis Of Malaria And Cutaneous Leishmaniasis Infection, O. A. Adegboye, M. Al-Saghir, Denis H. Y. Leung

Research Collection School Of Economics

Malaria and leishmaniasis are among the two most important health problems of many developing countries especially in the Middle East and North Africa. It is common for vector-borne infectious diseases to have similar hotspots which may be attributed to the overlapping ecological distribution of the vector. Hotspot analyses were conducted to simultaneously detect the location of local hotspots and test their statistical significance. Spatial scan statistics were used to detect and test hotspots of malaria and cutaneous leishmaniasis (CL) in Afghanistan in 2009. A multivariate negative binomial model was used to simultaneously assess the effects of environmental variables on malaria …

Shrinkage Empirical Likelihood Estimator In Longitudinal Analysis With Time-Dependent Covariates: Application To Modeling The Health Of Filipino Children, Denis H. Y. Leung, Dylan S. Small, Jing Qin, Min Zhu

Research Collection School Of Economics

The method of generalized estimating equations (GEE) is a popular tool for analysing longitudinal (panel) data. Often, the covariates collected are time-dependent in nature, for example, age, relapse status, monthly income. When using GEE to analyse longitudinal data with time-dependent covariates, crucial assumptions about the covariates are necessary for valid inferences to be drawn. When those assumptions do not hold or cannot be verified, Pepe and Anderson (1994, Communications in Statistics, Simulations and Computation 23, 939–951) advocated using an independence working correlation assumption in the GEE model as a robust approach. However, using GEE with the independence correlation assumption may …

Efficient Parameter Estimation In Longitudinal Data Analysis Using A Hybrid Gee Method, Denis H. Y. Leung, You Gan Wang, Min Zhu

Research Collection School Of Economics

The method of generalized estimating equations (GEEs) provides consistent estimates of the regression parameters in a marginal regression model for longitudinal data, even when the working correlation model is misspecified (Liang and Zeger, 1986). However, the efficiency of a GEE estimate can be seriously affected by the choice of the working correlation model. This study addresses this problem by proposing a hybrid method that combines multiple GEEs based on different working correlation models, using the empirical likelihood method (Qin and Lawless, 1994). Analyses show that this hybrid method is more efficient than a GEE using a misspecified working correlation model. …

Multiple Testing To Establish Superiority/Equivalence Of A New Treatment Compared With K Standard Treatments For Unbalanced Designs, Koon Shing Kwong, Siu Hung Cheung, Wai-Sum Chan

Research Collection School Of Economics

In clinical studies, multiple superiority/equivalence testing procedures can be applied to classify a new treatment as superior, equivalent (same therapeutic effect), or inferior to each set of standard treatments. Previous stepwise approaches (Dunnett and Tamhane, 1997, Statistics in Medicine 16, 2489–2506; Kwong, 2001, Journal of Statistical Planning and Inference 97, 359–366) are only appropriate for balanced designs. Unfortunately, the construction of similar tests for unbalanced designs is far more complex, with two major difficulties: (i) the ordering of test statistics for superiority may not be the same as the ordering of test statistics for equivalence; and (ii) the correlation structure …

A Semi-Parametric Two-Component Compound Mixture Model And Its Application To Estimating Malaria Attributable Fractions, Jing Qin, Denis H. Y. Leung

Research Collection School Of Economics

Malaria remains a major epidemiologic problem in many developing countries. Malaria is defined as the presence of parasites and symptoms (usually fever) due to the parasites. In endemic areas, an individual may have symptoms attributable either to malaria or to other causes. From a clinical viewpoint, it is important to correctly diagnose an individual who has developed symptoms so that the appropriate treatments can be given. From an epidemiologic and economic viewpoint, it is important to determine the proportion of malaria-affected cases in individuals who have symptoms so that policies on intervention program can be developed. Once symptoms have developed …

Adrenocortical Adenoma And Carcinoma: Histopathological And Molecular Comparative Analysis, A. Stojadinovic, M. F. Brennan, A. Hoos, A. Omeroglu, Denis H. Y. Leung, M. Dudas, A. Nissan, C. Cordon-Cardo, R.A. Ghossein

Research Collection School Of Economics

We compared histomorphological features and molecular expression profiles of adrenocortical adenomas (ACAd) and carcinomas (ACCa). A critical histopathological review (mean, 11 slides per patient) was conducted of 37 ACAd and 67 ACCa. Paraffin-embedded tissue cores of ACAd (n = 33) and ACCa (n = 38) were arrayed in triplicate on tissue microarrays. Expression profiles of p53, mdm-2, p21, Bcl-2, cyclin D1, p27, and Ki-67 were investigated by immunohistochemistry and correlated with histopathology and patient outcome using standard statistical methodology. Median follow-up period was 5 years. Tumor necrosis, atypical mitoses, and >1 mitosis per 50 high-power fields were factors that were …

Factors Influencing Treatment Patterns In Breast Cancer Patients Age 75 And Over, Arti Hurria, Denis H. Y. Leung, Kathleen Trainor, Patrick Borgen, Larry Norton, Clifford Hudis

Research Collection School Of Economics

To retrospectively determine the factors influencing treatment decisions in older breast cancer patients at a single center. Experimental Design: 216 patients age > or = 75 seen in post-treatment follow-up between January, 1997 and June, 2000 were identified in the Memorial Sloan-Kettering breast cancer database. Eligible patients were > or = 75 years old at diagnosis, had a diagnosis of stage I, II, or III breast cancer, and received their follow-up care at Memorial Sloan Kettering Cancer Center. A retrospective chart review was performed. Patients were stratified by: (1) prognostic factors (age (75-79 or > or = 80), Charlson comorbidity score, tumor size, …

Antifibrinolytic Therapy And Perioperative Blood Loss In Cancer Patients Undergoing Major Orthopedic Surgery, David Amar, Florence M. Grant, Hao Zhang, Patrick J. Boland, Denis H. Y. Leung, John A. Healey

Research Collection School Of Economics

Background: Aprotinin has been reported to reduce blood loss and transfusion requirements in patients having major orthopedic operations. Data on whether epsilon amino-caproic acid (EACA) is effective in this population are sparse.

Methods: Sixty-nine adults with malignancy scheduled for either pelvic, extremity or spine surgery during general anesthesia entered this randomized, double-blind, placebo-controlled trial, and received either intravenous aprotinin (n = 23), bolus of 2 x 10(6) kallikrein inactivator units (KIU), followed by an infusion of 5 x 10(5) KIU/h, or EACA (n = 22), bolus of 150 mg/kg, followed by a 15 mg/kg/h infusion or saline placebo (n = …

Isotonic Designs For Phase I Trials, Denis H. Y. Leung, You-Gan Wang

Research Collection School Of Economics

The purpose of a phase I trial in cancer is to determine the level (dose) of the treatment under study that has an acceptable level of adverse effects. Although substantial progress has recently been made in this area using parametric approaches, the method that is widely used is based on treating small cohorts of patients at escalating doses until the frequency of toxicities seen at a dose exceeds a predefined tolerable toxicity rate. This method is popular because of its simplicity and freedom from parametric assumptions. In this paper, we consider cases in which it is undesirable to assume a …

Clinical Significance Of Molecular Expression Profiles Of Hürthle Cell Tumors Of The Thyroid Gland Analyzed Via Tissue Microarrays, A. Hoos, A. Stojadinovic, B. Singh, M. Dudas, Denis H. Y. Leung, A. Shaha

Research Collection School Of Economics

Hürthle cell tumors are rare thyroid neoplasms for which disease biology is poorly understood and diagnosis of carcinoma can be challenging. The aim of the study was to characterize molecular expression profiles of Hürthle cell tumors and to determine the clinical significance of identified phenotypes. Paraffin-embedded tissue cores of normal thyroid (n = 18), and histopathologically well-defined Hürthle cell adenomas (n = 27), Hürthle cell tumors of unknown malignant behavior (n = 7), and minimally (n = 14) and widely (n = 21) invasive Hürthle cell carcinomas were arrayed in triplicate on tissue microarrays. Expression profiles of p53, mdm-2, p21, …

Prognostic Impact Of P53 Status, Tls-Chop Fusion Transcript Structure, And Histological Grade In Myxoid Liposarcoma: A Molecular And Clinicopathologic Study Of 82 Cases, C. R. Antonescu, S. J. Tschernyavsky, R. Decuseara, Denis H. Y. Leung, J. M. Woodruff, M. F. Brennan, J. A. Bridge, J. R. Neff, J. R. Goldblum, M. Ladanyi

Research Collection School Of Economics

Purpose: A specific TLS-CHOP fusion gene resulting from the t(12;16) is present in at least 95% of myxoid liposarcomas (MLS). Three common forms of the TLS-CHOP fusion have been described, differing by the presence or absence of TLS exons 6-8 in the fusion product. Type 5-2 (also known as type II) consists of TLS exons 1-5 fused to CHOP exon 2; type 7-2 (also known as type I) also includes TLS exons 6 and 7 in the fusion, whereas type 8-2 (also known as type III) fuses TLS exons 1-8 to CHOP exon 2. We sought to determine the impact …

Validation Of Tissue Microarrays For Immunohistochemical Profiling Of Cancer Specimens Using The Example Of Human Fibroblastic Tumors, Axel Hoos, M. J. Urist, A. Stojadinovic, S. Mastorides, M. Dudas, Denis H. Y. Leung

Research Collection School Of Economics

Tissue microarrays allow high-throughput molecular profiling of cancer specimens by immunohistochemistry. Phenotype information of sections from arrayed biopsies on a multitissue block needs to be representative of full sections, as protein expression varies throughout the entire tumor specimen. To validate the use of tissue microarrays for immunophenotyping, we studied a group of 59 fibroblastic tumors with variable protein expression patterns by immunohistochemistry for Ki-67, p53, and the retinoblastoma protein (pRB). Data on full tissue sections were compared to the results of one, two, and three 0.6-mm core biopsies per tumor on a tissue array. Ki-67 and p53 staining was read …

Optimal Designs For Evaluating A Series Of Treatments, Denis H. Y. Leung, You Gan Wang

Research Collection School Of Economics

Several articles in this journal have studied optimal designs for testing a series of treatments to identify promising ones for further study. These designs formulate testing as an ongoing process until a promising treatment is identified. This formulation is considered to be more realistic but substantially increases the computational complexity. In this article, we show that these new designs, which control the error rates for a series of treatments, can be reformulated as conventional designs that control the error rates for each individual treatment. This reformulation leads to a more meaningful interpretation of the error rates and hence easier specification …

A Bayesian Decision Approach For Sample Size Determination In Phase Ii Trials, Denis H. Y. Leung, You-Gan Wang

Research Collection School Of Economics

Stallard (1998, Biometrics54, 279–294) recently used Bayesian decision theory for sample-size determination in phase II trials. His design maximizes the expected financial gains in the development of a new treatment. However, it results in a very high probability (0.65) of recommending an ineffective treatment for phase III testing. On the other hand, the expected gain using his design is more than 10 times that of a design that tightly controls the false positive error (Thall and Simon, 1994, Biometrics50, 337–349). Stallard's design maximizes the expected gain per phase II trial, but it does not maximize the rate of gain or …

Prognostic Impact Of P53 Status In Ewing Sarcoma, E. De Alava, C. Antonescu, A. Panizo, Denis H. Y. Leung, P. Meyers, A. Huvos, F. J. Pardo-Mindan, J. Healey, M. Ladanyi

Research Collection School Of Economics

Disease stage at the time of diagnosis and response to therapy are the main prognostic factors for patients with Ewing sarcoma or peripheral neuroectodermal tumor (ES/PNET). The primary genetic alteration in ES/PNET, the fusion of the EWS gene with FLI1 or ERG, is diagnostically highly specific for these tumors, and molecular variation in the structure of the EWS-FLI1 fusion gene also is of prognostic significance. In contrast, secondary genetic alterations, such as P53 alterations, are relatively uncommon in ES/PNET, and their prognostic impact has not been extensively studied. METHODS: Prechemotherapy, paraffin embedded, nondecalcified, primary tumor material in a well-characterized series …

Two Hundred Gastrointestinal Stromal Tumors: Recurrence Patterns And Prognostic Factors For Survival, Ronald P. Dematteo, Jonathan J. Lewis, Denis H. Y. Leung, Salvinder S. Mudan, James M. Woodruff, Murray F. Brennan

Research Collection School Of Economics

Objective: To analyze the outcome of 200 patients with gastrointestinal stromal tumor (GIST) who were treated at a single institution and followed up prospectively. Summary Background Data: A GIST is a visceral sarcoma that arises from the gastrointestinal tract. Surgical resection is the mainstay of treatment because adjuvant therapy is unproven. Methods: Two hundred patients with malignant GIST were admitted and treated at Memorial Hospital during the past 16 years. Patient, tumor, and treatment variables were analyzed to identify patterns of tumor recurrence and factors that predict survival. Results: Of the 200 patients, 46% had primary disease without metastasis, 47% …

The Long Term Effects Of Angiotensin Converting Enzyme Inhibition And Metabolic Control On Cardiovascular And Renal Outcomes In Hypertensive Type 2 Diabetic Patients, Julien C. N. Chan, Gary T. C. Ko, Denis H. Y. Leung

Research Collection School Of Economics

Long-term effects of angiotensin-converting enzyme inhibition and metabolic control in hypertensive type 2 diabetic patients. Background. In hypertensive type 2 diabetic patients, treatment with angiotensin-converting enzyme (ACE) inhibitors is associated with a lower incidence of cardiovascular events than those treated with calcium channel-blocking agents. However, the long-term renal effects of ACE inhibitors in these patients remain inconclusive. In 1989, we commenced a placebo-controlled, double-blind, randomized study to examine the anti-albuminuric effects of enalapril versus nifedipine (slow release) in 102 hypertensive, type 2 diabetic patients. These patients have been followed up for a mean trial duration of 5.5 ± 2.2 years. …

Rearrangement Of The Bcl-6 Gene As A Prognostic Marker In Diffuse Large-Cell Lymphoma, K. Offit, D.C. Louie, N. Z. Parsa, Denis H. Y. Leung, C. Portlock, B.H. Ye, F. Lista, D.A. Filippa, A. Rosenbaum, M. Ladanyi, S. Jhanwar, R. Dalla-Favera, R.S.K. Changanti

Research Collection School Of Economics

Current therapy can induce a long-term remission in half the patients with diffuse lymphomas with a large-cell component (DLLC), but more intensive treatment has the potential to improve outcome. Rearrangement of a novel candidate proto-oncogene, bcl-6, correlates with a favorable clinical outcome in DLLC and may thus serve as a prognostic marker.