Research: Abdus S. Wahed

 

Research Interests

Publications

Presentations

Students

Resources

 

 

 

 

 

·   Dynamic treatment sequencing

·   Skew-symmetric distributions

·   Hepatitis C

·   Critical Care

·   Bariatric Surgery

·   Alzheimer’s research

·   Methods

·   Collaboration

·       Invited

·       Others

 

 

Codes

Macros

Dynamic treatment sequencing or adaptive treatment strategies:

 

Treatment of complex diseases such as cancer, leukemia, AIDS and depression usually follows complex treatment regimes consisting of a sequence of pre- and post-remission therapies. An adaptive treatment strategy (ATS), sometimes referred to as a dynamic treatment regime is a sequence of individually tailored treatments. Under an ATS, during the treatment period individuals receive time-varying treatment based on their health status and other eligibility criteria specified prior to the start of the treatment. An example might be the cases where patients are treated with one of several available treatments (or different doses of same drug) for a fixed period of time and then based on the intermediate response are switched to a different treatment. Another example of the application of such dynamic treatment regime is where patients receive an induction therapy and among those who achieve remission receive some form of maintenance therapy.

 

While making treatment decisions at each stage, a physician looks at multiple factors including (i) treatments assigned in prior stages (ii) response to the treatments in prior stage (iii) health status (quality of life) of the patient and (iv) possible treatments the patient is eligible for at that particular stage. The goal at each stage is to decide on the treatment which will result in largest short/long-term benefit. If the number of stages and the number of treatment options at each stage are small, sequential multiple assignment randomization trials could be used to compare different treatment strategies. My main research interest is efficient estimation of survival distributions under treatment strategies and comparison of multiple treatment strategies based on observational or randomized studies.

 

In the year 2007, we have formed a reading group to accelerate our research in this area. Please visit the reading group website Adaptive Treatment Strategy Reading Group.

 

 

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Skew-symmetric distributions

 

In recent years, there has been considerable interest among investigators in the construction of general class of skewed distributions which includes the standard symmetric distributions such as the normal, t, logistic and Cauchy distributions. The key is to introduce additional parameters or parametric functions in the distributional form that accounts for the skewness of the distribution. The idea became institutionalized when Azzalini (1985) defined a class of distribution (which he referred to as skew-normal) by introducing an additional skewness parameter that included the normal distribution as a special case. The name suggests that this distribution, unlike the normal distribution, is asymmetric in general and allows both positively and negatively skewed distributions. Subsequently, Azzalini and Dalla Valle (1996) came up with the multivariate version of the skew-normal distribution. A statistical application of the multivariate skew-normal distribution was considered by Azzalini and Capitanio (1999). This paper popularized the application of such distributions and led the way for others to define similar families of distributions based on other symmetric distributions such as skew-Cauchy (Arnold and Beaver, 2000a; Wahed, 2000), skew-t (Wahed, 2000; Branco and Dey, 2001), skew-logistic (Wahed and Ali, 2001), curvi-triangular (Wahed, 2007). Although other generalizations from different points of view have been considered among others by Arnold and Beaver (2002a), Arellano-Valle, del Pino and San Martin (2002), Genton and Loperfido (2002), the one advocated by Azzalini (1985, 1986) has been used most commonly in the literature. My research in this area focuses on construction of skewed distributions and their application in biostatistical settings.

 

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Research with Hepatitis C Virus (HCV)

 

My research with HCV is a result of my collaboration in the clinical trials/studies coordinated by the Epidemiology Data Center at GSPH. Currently I am supervising the statistical activities (data management and analysis) of the multi-center study VIRAHEP-C (Viral Resistance to Antiviral Therapy in Hepatitis C). The main aim of the study is to compare the response rates between African Americans and Caucasian Americans to the combination therapy (pegnterferon alpha-2a and ribavirin). The study has different sub-components such as viral kinetics, immunology, HCV sequencing and host genetics.  In addition to the collaboration, currently I am pursuing methodological research motivated from my collaboration in this project related to the non-linear modeling and modeling longitudinal truncated data.

 

In addition, currently I am a co-investigator in a Phase I/II clinical trial (SYNCH) sponsored by NIDDK and NCAM to investigate the safety and efficacy of silymarin as a treatment for hepatitis C.

 

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Longitudinal Assessment of Bariatric Surgery (LABS)

 

The Longitudinal Assessment of Bariatric Surgery (LABS) is a National Institutes of Health (NIH)-funded consortium of six clinical centers and a data coordinating center working in cooperation with NIH scientific staff to plan, develop, and conduct coordinated clinical, epidemiological, and behavioral research in the field of bariatric surgery. Recently I joined this group as a statistician.

 

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Critical Care

 

Recently I started collaborating with Clinical Research, Investigation, and Systems Modeling of Acute Illness Laboratory  (CRISMA) as a statistician. CRISMA is directed by Derek C. Angus MD, MPH, and co-directed by Gilles Clermont MD, MSc. This large team of clinicians, mathematicians, and epidemiologists enjoys superb funding from the NIH and multiple industrial sponsors. Regarded by many around the world as the leading investigative team carrying out studies of the clinical epidemiology of critical illness, Dr. Angus and his colleagues are actively studying the genetics of human sepsis, a syndrome that affects about 750,000 Americans every year and carries a mortality rate of almost 30 percent. Dr. Angus and his team of scientists have published papers in leading journals such as JAMA, Lancet, Critical Care Medicine, and the American Journal of Respiratory and Critical Care Medicine. I mainly collaborate with John Kellum in HIDONOR and MONiTOR study.

 

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Alzheimer’s research

Hepatitis B Clinical Research Network

Weight Control in Young Adults

 

 

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Publications

 

Methodology

1.      Kidwell, KM and Wahed, AS (2011). Weighted Log-rank Statistic to Compare Shared-Path Adaptive Treatment Strategies. In revision, Technical Draft

2.      Wahed, AS and Thall, PF (2012). Evaluating Joint E_ects of Induction-Salvage Treatment Regimes on Overall Survival in Acute Leukemia. In Press, Journal of Royal Statistical Society, Series C.

3.      Ko, JH, and Wahed, AS (2012). Up-front vs. Sequential Randomizations for Inference on Adaptive Treatment Strategies, Statistics in Medicine, Volume 31, Issue 9, pages 812–830, 30 April 2012.

4.      Tang, X, and Wahed, AS (2011). Comparison of Treatment Regimes with Adjustment for Auxiliary Variables. Journal of Applied Statistics, 2011; 38: 2925-2938.

5.      Wahed, AS (2011). On the Equivalence of Inverse-Probability-of-Censoring-Weighted and Kaplan-Meier Estimators. Invited Article, Journal of the Applied Statistical Science, Volume 18, Issue 4.

6.      Miyahara, S, and Wahed, AS (2010). Weighted Kaplan-Meier Estimators for Two-Stage Treatment Regimes. Statistics in Medicine, 2010; 29: 2581-2591.

7.      Wahed , AS (2010). Inference for Two-Stage Adaptive Treatment Strategies Using Mixture Distributions. Journal of Royal Statistical Society Series C (Applied Statistics) Appl. Statist. (2010)  59.

8.      Feng, W and Wahed, AS (2009). Sample Size for Two-Stage Studies with Maintenance Therapy. Statistics in Medicine, 2009; 28: 2028-2041

9.      Wahed, AS ,Luong, T, and Jeong, J-H (2009). A new generalization of Weibull distribution with application to a breast cancer data set. Accepted, Statistics in Medicine, 2009; 28: 2077-2094

  1. Wahed, AS (2009). Estimation of survival quantiles in two-stage randomization designs, Journal of Statistical Planning and Inference 139 (2009) 2064 – 2075.
  2. Feng, W and Wahed, AS (2008). A supremum log rank test for comparing adaptive treatment strategies and corresponding sample size formula, Biometrika. 95, 3, pp. 695-707.

12.  Ali, MM, Woo, J, Pal, M and Wahed, AS. (2008)  Some Skew-Symmetric Double Inverted Distributions. International Journal of Statistical Sciences. Vol. 7, pp. 1-12.

13.  Wahed, AS. (2007)  The family of curvi-triangular distributions. International Journal of Statistical Sciences, Vol 6, pp 7-18.

14.  Wahed, AS and Tsiatis, A. A. (2006) Semi-parametric Efficient Estimation of The Survival Distribution for Treatment Policies in Two-Stage Randomization Designs in Clinical Trials with Censored Data. Biometrika Vol 93: pp. 147-161.

15.  Wahed, AS. (2006)  Bayesian Inference Using Burr Model Under Asymmetric Loss Function: An Application to Carcinoma Survival Data. Journal of Statistical Research, 2006, Vol. 40, No. 1, pp. 45-57.

16.  Wahed, AS. (2006). A General Method of Constructing Extended Families of Distributions from an Existing Continuous Class. Journal of Probability and Statistical Science 4(2), 165-177.

17.  Feng, W and Wahed, AS (2006). A Review of Inferential Procedures for Survival Analysis in Two-Stage Randomization Designs. Far East Journal of Theoretical Statistics Vol. 19 (1), pp 117 – 139.

18.  Wahed, AS and Tsiatis, A. A.(2004). Optimal estimator for the survival distribution and related quantities for treatment policies in two-stage randomization designs in clinical trials, Biometrics, Vol. 60, No. 1. pp 124-133.

19.  Wahed, AS and Ali, MM (2001). The Skew-Logistic Distribution. Journal of Statistical Research, Vol. 35, No,2, pp. 71-80.

20.  Wahed, AS and Uddin, B (1998). Bayes Estimation Under Asymmetric Loss. Dhaka University Journal of Science, Vol. 46.

Collaboration

 

  1. Fried, MW, Navaro, VJ, Afdhal, N, Belle, SH, Wahed, AS, et. al., Effect of Silymarin (Milk Thistle) on Liver Disease in Patients With Chronic Hepatitis C Unsuccessfully Treated With Interferon Therapy A Randomized Controlled Trial. JAMA. 2012;308(3):274-282
  2. Sarkar, S, Jiang, Z, Evon, DM, Wahed, AS, and Hoofnagle, JH. (2012) Fatigue Before, During and After Antiviral Therapy of Chronic Hepatitis C: Results from the Virahep-C Study, Accepted, Journal of Hepatology.
  3. Greenstein, AJ, Wahed, AS, Adeniji, A, et al. (2012).  Prevalence of Adverse Intra-operative Events during Obesity Surgery and their Sequelae. 2012 May 25. [Epub], Journal of the American College of Surgeons
  4. Reddy KR, Belle, SH, …..,Wahed, AS et al. for the SyNCH Study Group (2011). Rationale, Challenges and Participants in a Phase II Trial of a Botanical Product for Chronic Hepatitis C, Clin Trials. 2012 February; 9(1): 102–112.
  5. Schrieber, SJ, Hawke, RL, …, Wahed, AS et al. for The SyNCH Trial Group (2011). Differences in the Disposition of Silymarin Between Patients with Non-Alcoholic Fatty Liver Disease and Chronic Hepatitis C. Drug Metab. Disp. 2011, vol. 39, 12, pp. 2182-2190
  6. Murugan, R, Sileanu, F, Wahed, AS, et al. (2011). Sex Difference in Deceased Donor Organ Transplantation, accepted, Transplantation, 2011 Dec 15;92(11):1278-84
  7. Smith, MD, Patterson, E, and Wahed, AS et al. (2011). 30-day Mortality after Bariatric Surgery: Independently Adjudicated Causes of Death in the Longitudinal Assessment of Bariatric Surgery. Obesity Surgery, 2011 Nov;21(11):1687-92.
  8. Ramcharran, D, Yee, LJ, Wahed, AS et al. (2011). Serum lipids and their associations with viral levels and liver disease severity in a treatment naďve chronic hepatitis C type 1 infected cohort. J Viral Hepat. 2011 Apr;18(4):e144-e152
  9. Conjeevaram, HS, Wahed, AS, Afdhal, N, et al. (2011). Changes in insulin sensitivity and body weight during and after peginterferon and ribavirin therapy of chronic hepatitis C. Gastroenterology. 2011 Feb;140(2):469-77.
  10. Smith, M.D., Patterson, E., Wahed, A.S., Belle, S.H., Bessler, M., Courcoulas, A.P., Flum, D., Mitchell, J.E., Pomp, A., Pories, W.J., Wolfe, B (2010). Response to Livingston, EH Letter to the Editor regarding: There is an Inverse Relationship between Surgeon Volume and Adverse Outcomes after RYGB in the Longitudinal Assessment of Bariatric Surgery (LABS) Study, Surgery for Obesity and Related Diseases, (2009), doi: 10.1016/j.soard.2010.07.001.
  11. Ramcharran, D, Wahed, AS, Conjeevaram, HS et al. (2010). Associations between serum lipids and hepatitis C antiviral treatment efficacy. Hepatology. 2010 Sep;52(3):854-63.
  12. Donlin MJ, Cannon NA, Aurora R, Li J, Wahed AS, et al. (2010) Contribution of Genome-Wide HCV Genetic Differences to Outcome of Interferon-Based Therapy in Caucasian American and African American Patients. PLoS ONE 5(2): e9032. doi:10.1371/journal.pone.0009032
  13. Inabnet WB, Belle, SH, …, Wahed, AS et al. (2010). A comparison of 30 day outcomes after non-lap Band primary and revisional bariatric surgical procedures from the Longitudinal Assessment of Bariatric Surgery (LABS) study. Surgery for Obesity and Related Diseases DOI: 10.1016/j.soard.2009.10.007
  14. [Longitudinal Assessment of Bariatric Surgery (LABS) Consortium] (2009). Reply to the letters from Vetter, ML,  et al. (2009) and Bhattacharyya, S, et al. (2009) [In response to Peri-operative Safety in the Longitudinal Assessment of Bariatric Surgery. New England Journal of Medicine. Volume 361:445-454  July 30, 2009  Number 5] Accepted, New England Journal of Medicine.
  15. [Longitudinal Assessment of Bariatric Surgery (LABS) Consortium] Flum, D, Belle, SH,….., Wahed, AS et al. (2009). Peri-operative Safety in the Longitudinal Assessment of Bariatric Surgery. New England Journal of Medicine. Volume 361:445-454  July 30, 2009  Number 5.
  16. Hoofnagle, JH, Wahed, AS, and Belle, SH (2009). Reply to Antonucci et al. (in response to Hoofnagle, JH, Wahed, AS, et al. (2009) below). Journal of Infectious Diseases 2009; 200:1485.
  17.  Smith, MD,…., Wahed, AS et al. (2009). The Relationship between Surgeon Volume and Adverse Outcomes after RYGB in the Longitudinal Assessment of Bariatric Surgery (LABS) Study. Accepted, Surgery for Obesity and Related Diseases.
  18. Hawke, R, …,Wahed, AS, et al. (2009). Silymarin Ascending Multiple Oral Dosing Phase I Study in Non-Cirrhotic Patients with Chronic Hepatitis C. Accepted, Journal of Clinical Pharmacology.
  19. Dove, LM, Rosen, RC, Ramacharran, D, Wahed, AS et al. (2009). Decline in Male Sexual Desire, Function, and Satisfaction During and After Antiviral Therapy for Chronic Hepatitis C. Gastroenterology, 137 (3); 873-884.

 

  1. Iuliano, D, Feingold, E, Wahed AS et al. (2009). Host Genetics, Steatosis and Insulin Resistance among African Americans and Caucasian Americans with Hepatitis C Virus Genotype-1 Infection. Intervirology 2009;52:49-56 

 

  1. Lopez, OL, Becker, JT, Wahed, AS, Saxton, J, Sweet, RA, Wolk, D, Klunk, W, and DeKosky, ST (2009). Concomitant use of memantine and cholinesterase inhibition in the treatment of Alzheimer's disease. J Neurol Neurosurg Psychiatry. 2009 Mar 29.

 

  1. Murugan, R, Venkataraman, R, Wahed, AS et al. (2009).  Preload Responsiveness is associated with Increased IL- 6 and Lower Organ Yield from Cadaveric Donors. Critical care medicine 37(8):2387-93, 2009

 

  1. Yee, LJ, Im, K, Wahed, AS et al. for the Virahep-C Study Group (2009). Polymorphism in the human MHC and the early viral decline during treatment of chronic hepatitis C, Antimicrob. Agents Chemother. Feb 2009, p 615-621.

 

  1. Ling, B, Schoen, RE, Trauth, JM, Wahed, AS,  et al. (2009). Physicians Encouraging Colorectal Screening (PECS): A randomized controlled trial of enhanced office and patient management on compliance with colorectal cancer screening, Arch Intern Med. 2009;169(1):47-55

 

  1. Hoofnagle, JH, Wahed, AS, Brown, RS, Howell, CD, Belle, SH for the Virahep-C Study Group (2009). Early Changes in Hepatitis C Viral Levels in Response to Peginterferon and Ribavirin in Patients with Chronic Hepatitis C, Genotype 1 Infection, The Journal of Infectious Diseases 2009; 199:1112–20.

 

  1. Murugan, R, Venkataraman, R, Wahed, AS, Elder, M, Hergenroeder, G, Carter, M, Madden, NJ, Powner, D, Kellum, JA On behalf of the HIDonOR Study Investigators (2008). Increased plasma IL-6 in donors is associated with lower recipient hospital-free survival after cadaveric organ transplantation. Crit Care Med 2008; 36:1810–1816.

 

  1. Golden-Mason, L, Klarquist, J, Wahed, AS, and Rosen, HR  for the Virahep-C Study Group (2008). PD-1 Expression is Increased on Immunocytes in Chronic HCV and Predicts Failure of Response to Antiviral Therapy: Race-Dependent Differences. J. Immunol. 180: 3637-3641.

 

  1. Dowling, TC, Wahed, AS, Paul, M, Terrault, NA, Taylor, M, Jeffers, L, Hoofnagle, JH, and Howell, CD for the Virahep-C Study Group (2008). Peginterferon Pharmacokinetics in African American and Caucacian American Patients with Hepatitis C Virus Genotype 1 Infection, CLINICAL GASTROENTEROLOGY AND HEPATOLOGY 2008;6:575–583.

 

  1. Donlin, MJ, Cannon, NA, Yao,E, Li, J, Wahed, A, Taylor, MW, Belle, S, Di Bisceglie, AM, Aurora, R, and Tavis, JE for the Virahep-C Study Group (2007). Pretreatment Sequence Diversity Differences in the Full-Length Hepatitis C Virus Open Reading Frame Correlate with Early Response to Therapy. J. Virol. 2007 81: 8211-8224.

 

  1. Brodsky LI, Wahed AS, Li J, Tavis JE, Tsukahara T, et al (2007) A Novel Unsupervised Method to Identify Genes Important in the Anti-viral Response: Application to Interferon/Ribavirin in Hepatitis C Patients. PLoS ONE 1(1): e584. doi:10.1371/journal.pone.0000584

 

  1. Smith, SR, Wahed, AS, Kelley, SS, Conjeevaram, HS, Robuck, PR, Fried, MR  for the Virahep-C Study Group (2007). Assessing the Validity of Self-Reported Medication Adherence in HCV Treatment. Ann Pharmacother.2007; 41: 1116-1123.

 

  1. Yee, LJ, Tang, Y, Kleiner, DE, Wang, D, Im, K, Wahed, AS, Tong, X, Rhodes, S, Su, X, Whelan, MR, Ghany, MG, Borg, B, Fontana, RJ, Liang, J and Yang, H for the Virahep-C Study Group (2007). Mxyovirus-1 (Mx1) and protein kinase (PKR) haplotypes and fibrosis in chronic HCV, Hepatology, 2007, 46 (1): 74-83.

 

  1. Conjeevaram HS, Kleiner DE, Everhart JE, Hoofnagle JH, Zacks S, Afdhal NH, Wahed AS for the Virahep-C Study Group (2007). Race, Insulin Resistance and Hepatic Steatosis in chronic hepatitis C. Hepatology. 2007 Jan;45(1):80-7

Other publications

  1. Wahed, AS (2010). Unbiased Estimator. Encyclopedia of Research Design. Edited by Neil J. Salkind, Sage Publications, Newbury Park, CA.

 

  1. Wahed, AS (2010). Adaptive Designs in Clinical Trials. Encyclopedia of Research Design. Edited by Neil J. Salkind, Sage Publications, Newbury Park, CA.

 

  1. Wahed, AS and Miyahara, S. (2010). Group Sequential Designs in Clinical Trials. Encyclopedia of Research Design. Edited by Neil J. Salkind, Sage Publications, Newbury Park, CA.

 

  1. Wahed, AS and Tang, X.  (2010). Analysis of Variance. Encyclopedia of Research Design. Edited by Neil J. Salkind, Sage Publications, Newbury Park, CA.

 

  1. Wahed, AS and Hsu, J. (2010). Cause-and-Effect. Encyclopedia of Research Design. Edited by Neil J. Salkind, Sage Publications, Newbury Park, CA.

 

  1. Wahed, AS. (2006) "Censored Data". Entry in Encyclopedia of Measurement and Statistics. Sage Publications. (Amazon)

 

  1. Wahed, AS and Uddin B (1997). Empirical Bayes Estimator of Burr Parameters Based on the EM Algorithm. Statistics Preprint Series, School of Mathematics, University of New South Wales, Report S97-3, May 1997.

 

Invited Presentations

  1. June 2012. Study Designs. 29th Annual Meeting of the American Siciety of Metabolic and Bariatric Surgery, San Diego, California
  2. April 2012. Testing multiple adaptive treatment strategies in sequentially randomized clinical trials. Department of Biostatistics, University of Texas MD Anderson Cancer Center
  3. April 2012. Up-front vs. Sequential Randomization Designs for Comparing Adaptive Treatment Strategies. International Biometric Society (ENAR) spring meetings, 2012, Washington, DC.
  4. June 2011. Results from Virahep-C Study. SIBS Seminar, Department of Biostatistics, University of Pittsburgh
  5. June 2011. Personalized Medicine and Dynamic Treatment Regimes. Central Indiana Chapter of the American Statistical Association.
  6. June 2011. Risk Adjustment in Bariatric Surgery. 28th Annual Meeting of the American Society of Metabolic and Bariatric Surgery
  7. March 2011. Evaluating the Joint Effect of Induction-Salvage Treatment Regimes in the Treatment of Leukemia.  International Biometric Society (ENAR) spring meetings, 2011, Miami, Florida.
  8. December 2010. (Jointly with Dylan Small of U. of Pennsylvania) Causal inference in observational studies and sequentially randomized designs. Dhaka University Statistics Department Alumni Association, Dhaka, Bangladesh.
  9. December 2010. Accelerated failure time and proportional hazards models for sequentially randomized designs. Dhaka University Statistics Department Alumni Association, Dhaka, Bangladesh.
  10. November, 2010. Introduction to Survival Analysis (for non-statisticians).          UPMC Mercy Graduate Medical Education Program, UPMC Mercy, Pittsburgh.
  11. May, 2010. Statistical inference for treatment strategies from two-stage randomization designs when second randomization is delayed. 2010 ICSA Applied Statistics Symposium, Indianapolis, IN February, 2010.
  12. Adaptive Designs in Clinical Trials. School of Medicine, University of Pittsburgh

13.  December, 2009. Assessing the effect of treatment regimes on longitudinal outcome data. Department of Applied Statistics, University of Dhaka, Bangladesh

14.  December, 2009. A new generalization to the Weibull distribution with an application to a breast cancer dataset. 7th triennial statistics and probability conference, Kolkata, India

15.  November, 2009. Statistical methods for comparing dynamic treatment regimes with time-to-event endpoints. Department of Statistics, University of Pittsburgh

16.  November, 2009. Statistical methods for comparing dynamic treatment regimes with time-to-event endpoints. Center for Statistical Sciences, Brown University, RI

17.  August, 2009.    Dynamic Treatment regimes in Leukemia Treatment. Joint Statistical Meetings 2009, American Statistical Association.

18.  February, 2009. Adaptive Designs in Clinical Trials. School of Medicine, University of Pittsburgh.

19.  September, 2008. Comparing adaptive treatment strategies following sequential multiple assignment randomization trials, Clinical and Translational Sciences Research Institute, CHRC, RAND-Pittsburgh Institute, VA-CHERP.

20.  July, 2008. Inference on dynamic treatment regimes following sequential multiple assignment randomization trials, Center for Statistics at Queen Mary, University of London.

21.  February, 2008. Adaptive treatment strategies – one step forward towards individualized treatment rules. Dean’s Junior Faculty Seminar Series, Graduate School of Public Health, Pittsburgh.

22.  February, 2008. Adaptive Designs in Clinical Trials. School of Medicine, University of Pittsburgh.

23.  January 2008. Supremum weighted log-rank test and sample size for comparing two-stage adaptive treatment strategies. Department of Epidemiology, Biostatistics and Occupational Health, McGill University.

24.  June 2007. Semi-parametric methods for estimating causal effect of treatment strategies in two-stage randomization clinical trials.      ICSA 2007 Applied statistics Symposium, Raleigh, North Carolina.

25.  May 2007. Weibull-based approaches to survival analysis with applications to breast cancer data. Department of Mathematical Sciences, Ball State University, Muncie, Indiana.

26.  February 2007. Comparing Adaptive Treatment Strategies: Challenges and Solutions. Center for Health Equity, Research and Promotions (CHERP), VA Health Care System, Pittsburgh.

27.  December 2006. Survival Analysis for Comparing Adaptive Treatment Strategies. Department of Applied Statistics, University of Dhaka, Dhaka, Bangladesh.

28.  April 2006. Survival Analysis in Two-stage Randomization Designs in Leukemia Trials. Department of Mathematics and Statistics, University of Windsor, Windsor, Ontario.

29.  February 2006. Survival Analysis in Two-stage Randomization Designs in Oncolgy Trials. Invited presentation, Department of Biostatistics, College of Public Health, University of Kentucky.

30.  March 2005. Survival Analysis in Two-stage Randomization Designs. Invited lecture in the session CENSORED DATA IN THE ENVIRONMENTAL, AGRICULTURAL AND MEDICAL SCIENCES. International Biometric Society (ENAR) spring meetings, 2006, Tampa, Florida.

31.  March 2003. Optimal Estimator of the Survival Distribution and Related Quantities of Treatment Policies in Two-Stage Randomization Designs in Clinical Trials. University of Texas M.D. Anderson cancer Center.

32.  March 2003. Optimal Estimator of the Survival Distribution and Related Quantities of Treatment Policies in Two-Stage Randomization Designs in Clinical Trials. Department of Biostatistics, and Department of Statistics and Actuarial Science, University of Iowa.

33.  March 2003. Optimal Estimator of the Survival Distribution and Related Quantities of Treatment Policies in Two-Stage Randomization Designs in Clinical Trials. University of Pittsburgh Graduate School of Public Health.

34.  February 2003. Optimal Estimator of the Survival Distribution and Related Quantities of Treatment Policies in Two-Stage Randomization Designs in Clinical Trials. Boston University School of Public Health.

35.  February 2003. Optimal Estimator of the Survival Distribution and Related Quantities of Treatment Policies in Two-Stage Randomization Designs in Clinical Trials. Department of Biostatistics, University of Minnesota.

36.  February 2003. Optimal Estimator of the Survival Distribution and Related Quantities of Treatment Policies in Two-Stage Randomization Designs in Clinical Trials. Department of Health Studies, University of Chicago.

37.  February 2003. Optimal Estimator of the Survival Distribution and Related Quantities of Treatment Policies in Two-Stage Randomization Designs in Clinical Trials. Medical University of South Carolina.

38.  January 2003. Survival Analysis in Two-Stage Randomization Designs in Clinical Trials. Department of Mathematics and Statistics, Georgia State University.

39.  January 2003. Optimal Estimator of the Survival Distribution and Related Quantities of Treatment Policies in Two-Stage Randomization Designs in Clinical Trials. Department of Biostatistics and Epidemiology, University of Pennsylvania.

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Other presentations

 

1.         (with Kelley M. Kidwell) Weighted Log-rank Statistic to Compare Shared-path Adaptive Treatment Strategies. Joint Statistical Meetings, 2012, San Diego, CA.

2.          (with Xinxin Dong and Lan Kong) Accelerated Failure Time Model for Case-Cohort Design with Longitudinal Covariates Measured with Error. Joint Statistical Meetings, 2012, San Diego, CA.

3.         (with Kelley M. Kidwell) Weighted Log-rank Statistic to Compare Shared-path Adaptive Treatment Strategies. Society for Clinical Trials Annual Meeting, 2012, Orlando, FL.

4.         (with Abidemi K. Adeniji) Discrete Survival Analysis with Misclassified Events. International Biometric Society (ENAR) spring meetings, 2012, Washington, DC.

5.         (with Xinxin Dong and Lan Kong) Accelerated Failure Time Model for Case-Cohort Design with Longitudinal Covariates Measured with ErrorInternational Biometric Society (ENAR) spring meetings, 2012, Washington, DC.

6.          (with Kelley M. Kidwell) Weighted Log-rank Statistic to Compare Shared-path Adaptive Treatment Strategies. International Biometric Society (ENAR) spring meetings, 2012, Washington, DC.

7.         (poster with Chetachi A. Emeremni) Analysis of Variance for Right Censored Survival Data. International Biometric Society (ENAR) spring meetings, 2012, Washington, DC.

8.          (poster with Jesse Hsu) Causal Inference for Treatment Strategies from Two-Stage Randomization Designs. 34th  Midwest Biopharmaceutical Statistical Workshop, May 2010, Muncie, Indiana.

9.         (With Jinhui Ko) Nonparametric Estimation of Median Residual Life Function for Two-Stage randomization Designs. ENAR Spring meeting 2010.

10.     (With Xinyu Tang) Cox Proportional Hazard Model for Dynamic Treatment Regimes. ENAR Spring meeting 2010. 

11.     (poster with Jinhui Ko) Nonparametric Estimation of Median Residual Life Function for Two-Stage randomization Designs. 33rd  Midwest Biopharmaceutical Statistical Workshop, May 2009, Muncie, Indiana.

12.     (poster with Xinyu Tang) Statistical Methods for Sequentially Randomized Trials: An Application to High-Risk Neuroblastoma Study. 33rd  Midwest Biopharmaceutical Statistical Workshop, May 2009, Muncie, Indiana.

13.     Supremum Weighted Log-rank Test and Sample Size for Comparing Two-stage Adaptive Treatment Strategies, July 2008, International Biometric Conference, Dublin. 

14.     Inverse-probability-weighting-based sample size formula for comparing two-stage adaptive treatment strategies. ENAR Spring Meetings 2008, Crystal City, Virginia.

15.     Discussion on Two-Stage Treatment Strategies Based on Sequential Failure Times by Peter Thall (with Patricia Houck, and Jinhui Ko), ATSRG reading group meeting, November 2007, Department of Biostatistics, University of Pittsburgh Graduate School of Public Health. 

16.     (poster) Weighted Kaplan-Meier Estimator for Adaptive Treatment Strategies. SAMSI workshop on dynamic treatment regimes, June 2007, Statistical and Applied Mathematical Sciences Institute, RTP, North Carolina.

17.      (poster) Weibull-based approaches to survival analysis: an application to a breast cancer data set. 30th Midwest Biopharmaceutical Statistical Workshop, May 2007, Muncie, Indiana.

18.     A supremum log-rank test for two-stage adaptive treatment strategies and corresponding sample size formula, ENAR Spring Meetings 2007, Atlanta, GA (presented by Wentao Feng).

19.     Introduction to Adaptive Treatment Strategies with Examples (with Sachiko Miyahara). ATSRG reading group meeting, March 2007, Department of Biostatistics, University of Pittsburgh Graduate School of Public Health. 

20.     Likelihood Inference for Survival Analysis in Two-stage Randomization Designs, Joint Statistical Meetings, August 2006, Seattle, Washington

21.     (poster) Inferences for Treatment Regimes in Two Stage Clinical Trials, Midwest Biopharmaceutical statistics workshop, May 2006, Muncie, Indiana.

22.     (Poster) Insulin Resistance Is Independent Of Hepatic Steatosis and Is Augmented By Environmental Factors Such As Obesity in Patients With HCV Genotype 1 Infection, DDW, Chicago, Illinois, May 2005.

23.     Genetic variation in an interferon-stimulated gene, mxyovirus-1 (MxA), has a significant protective effect from fibrosis in genotype-1 chronic hepatitis C virus infection, DDW, Chicago, Illinois, May 2005.

24.     A non-linear mixed effect model for hepatitis C viral dynamics, International Biometric Society (ENAR) spring meetings, 2005, Austin, TX, March, 2005.

25.     A non-linear mixed effect model for hepatitis C viral dynamics, Joint Statistical Meetings 2004, Toronto, Canada, August 2004 (Presented on behalf of Dr. Wahed by K Im).

26.     Presented in the Faculty Seminar Series, Department of Biostatistics, University of Pittsburgh, October 2004.

27.     Race, Insulin Resistance, Visceral Adiposity and Hepatic Steatosis in Genotype 1 Patients with Chronic Hepatitis C, AASLD, November  2004 (poster).

28.     Efficient Estimation of the Survival Distribution for Treatment Policies in Two-Stage Randomization Designs in Clinical Trials with Censored Data. International Biometric Society (ENAR) meeting  2004, Pittsburgh, PA , April 2004.

29.     Optimal Estimator of the Survival Distribution and Related Quantities of Treatment Policies in Two-Stage Randomization Designs in Clinical Trials. Joint Statistical Meetings 2003, American Statistical Association, San Francisco, California, August 2003.

30.     Optimal Estimator of the Survival Distribution and Related Quantities of Treatment Policies in Two-Stage Randomization Designs in Clinical Trials. International Biometric Society (ENAR) meeting 2003, Tampa, Florida, April 2003.

 

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Students

· Shekhar Mehta, MS (2006)

Thesis title: Longitudinal Analysis of Renal Function using ZIP GEE on OLT Transplant Patients Undergoing NAC Prophylaxis

Current position: Entry position: Pharm.D program, University of Maryland School of Pharmacy

 

· Wentao Feng, PhD (2008)

Thesis title: Inference, Power and Sample Size Adaptive Treatment Strategies

Current position: Sr. Biostatistician, Novartis Pharmaceuticals Corporation

 

· Sachiko Miyahara, PhD (2009)

Thesis title: Statistical Inferences for Two-Stage Treatment Regimes for Time-To-Event and Longitudinal Data

Current position: Research Associate, Center for Biostatistics in AIDS Research, Department of Biostatistics, Harvard University

 

· Jinhui Ko, PhD (2010)

Thesis title: Statistical Issues in the Design and Analysis of Sequentially Randomized Trials

Entry position: Statistician, Biostatistics Solutions;

Current position: Statistician, GlaxoSmithKline

 

·Xinyu Tang, PhD (2010)

Thesis title: Analyzing Survival Data For Sequentially Randomized Designs

Current position: Assistant Professor, Department of Pediatrics, University of Arkansas, Little Rock 

 

·Jesse Hsu, PhD (2011)

Thesis title: Longitudinal Data Analysis in Depression Studies: Assessment of Intermediate-Outcome-Dependent Dynamic Interventions

Current position: Post-doctoral Associate, University of Pennsylvania, Wharton School

 

·Zhen Jiang, PhD (2011)

Thesis title: Joint Modeling of Multivariate Ordinal Longitudinal Outcome

Current position: Division of Biostatistics, Office of Biostatistics and Epidemiology, CBER, U.S. Food and Drug Administration

 

·Kelley Kidwell, PhD (2012)

Thesis title: Survival Analysis of Shared-Path Adaptive Treatment Strategies

Current position: Research Assistant Professor, University of Michigan, Department of Biostatistics.

 

·Abidemi Adeniji, PhD (2012).

Thesis title: Incorporating Diagnostic Accuracy into the Estimation of Discrete Survival Function

Current position: Statistician, Boehringer Ingelheim

 

·Chetachi Ememerni, PhD (2012).

Thesis title: Inference for Right Censored, and Right Censored Length Biased Data through Inverse Weighting

Current position: Assistant Professor of Pediatrics, and Preventive Medicine, The University of Tennessee Health Science Center

 

·Xinxin Dong (co-advisor with Dr. Lan Kong)

Expected Ph.D. graduation date: December 2012.

Thesis title: TBD

Current position: TBD

 

·Semhar Ogbagaber

Expected Ph.D. graduation date: 2013

Thesis title: TBD

Current position: TBD

 

·Emmanuel Sampene

Expected Ph.D. graduation date: 2013

Thesis title: TBD

Current position: TBD