Justine Shults, PhD
| Office Location | 610, Blockley Hall |
| Office Phone | 215-573-6526 |
| jshults@mail.med.upenn.edu | |
Faculty Information | |
| CCEB Appointment | Senior Scholar, Biostatistics |
| Primary Faculty Appointment | Associate Professor of Biostatistics at HUP, University of Pennsylvania SOM |
Research Statement
Dr. Shults is the currently the principal investigator of the NIH funded project "Longitudinal Analysis for Diverse Populations" (R01CA096885). Her work on this project involves quasi-least squares (QLS) that is based on Liang and Zeger's (1986) generalized estimating equation (GEE) approach. She participated in the three papers in which QLS was developed:
BRIEF DESCRIPTION OF QLS:
The method of quasi-least squares (QLS) is a two-stage approach in the framework of generalized estimating equations (GEE). Chaganty(JSPI, 1997) described stage one of QLS for an equal number of observations per subject (balanced data) and noted that "extensions of our results for unbalanced data... will appear elsewhere", e.g. the proof of feasibility for the first-order autoregressive AR(1) correlation structure (Appendix A) is based on the strum sequence for tridiagonal matrices and does not generalize readily for unbalanced data.
Shults (Doctoral Dissertation, "The Analysis of Unbalanced and Unequally Spaced Data using Quasi-Least Squares", 1996) and Shults and Chaganty (Biometrics, 1998) extended stage one by obtaining estimates that yield a positive definite matrix for several correlation structures (including the AR(1)) and unbalanced data. For example, the estimate provided in closed form for the equicorrelated structure in Chaganty (JSPI, 1997) only holds for balanced data; Shults (1996) obtained an estimating equation for unbalanced data and proved that this equation will always have a unique solution in the feasible region (interval on which the matrix is positive definite). For unbalanced data, this estimate can be obtained using the bisection method.
However, the stage one QLS estimate of the correlation parameter typically is not consistent, even if the correlation structure is correctly specified. Chaganty and Shults (JSPI, 1999) therefore introduced a second stage of QLS that provides a solution to an unbiased estimating equation for the correlation parameter. For more discussion of QLS that includes a comparison of stage one of QLS versus stage two and a comparison with other approaches, see Sun et al. 2006.
CURRENT RESEARCH FOCUS:
Dr. Shults' current focus is in extending QLS to allow for implementation of relatively complex patterned correlation structures that have not previously been applied for GEE. For example, in a recent paper with Ardythe Morrow, Ph.D (Biometrics 58: 521-530, 2002) the authors considered an international trial to promote exclusive breast-feeding in San-Pedro Martir, Mexico City. This study employed cluster randomization and followed mothers over time, to determine if they were exclusively breast-feeding their infants. As a result of the study design, there were two potential sources of correlation among the binary outcomes (breast-feeding yes/no) from this trial, in the sense that two measurements could be more similar, if they were collected within the same randomization group, or on the same subject. They adjusted for these two sources of correlation by directly modeling the association via a patterned correlation matrix constructed as the Kronecker product of two correlation matrices. She recently extended this approach for data with >2 sources of correlation in a manuscript with Melicia Whitt, Ph.D. and Shiriki Kumanyika, Ph.D (Analysis of data with multiple sources of correlation in the framework of generalized estimating equations. Statistics in Medicine. 23: 3209-3226, 2004.) Dr. Shults also recently worked with Carissa Mazurick, M.S. and Richard Landis, Ph.D. on implementation of a correlation structure appropriate for analysis of multiple bouts of repeated measurements, when the separation in time between bouts is large to the within bout separation in a mansucript that is in press in Statistics in Medicine (2006).
Courses Taught
Linear Models (2003, 2004, 2005, 2006)
Selected Publications
Morrow AL, Shults J, Pickering J. Criteria for publication of case reports. J Pediatr 122: 991-2, 1993.
Werner EJ, Broxson EH, Tucker, EL, Giroux DS, Shults J, Abshire TC. Prevalence of von Willebrand disease in children: a multi-ethnic study. J Pediatr 123: 893-8, 1993.
Bhisitkul DM, Morrow AL, Vinik AI, Shults J, Layland JC, Rohn R. Prevalence of stress hyperglycemia among patients attending a pediatric emergency department. J Pediatr 124: 547-51, 1994.
Bhisitkul DM, Vinik AI, Morrow AL, She J-X, Shults J, Powers AC, Maclaren NK. Prediabetic markers in children with stress hyperglycemia. Arch Pediatr Adolesc Med 150: 936-41, 1996.
Shults J, Chaganty NR. Analysis of serially correlated data using quasi-least squares. Biometrics 54: 1622-1630,1998.
Newburg DS, Peterson JA, Ruiz-Palacios GM, Matson DO, Morrow AL, Shults J, Guerrero ML, Chaturvedi P, Newburg SO, Scallan CD, Taylor MR, Ceriani RL, Pickering LK. Role of human-milk lactadherin in protection against symptomatic rotavirus infection. Lancet 351: 1160-1164, 1998.
Chaganty NR, Shults J. On eliminating the asymptotic bias in the quasi-least squares estimate of the correlation parameter. Journal of Statistical Planning and Inference. 76: 145-161, 1999.
Morrow AL, Guerrero ML, Shults J, Calva JJ, Morrow RC, Bravo J, Butterfoss FD, Lutter C. Efficacy of home-based peer counseling to promote exclusive breastfeeding: a randomized controlled trial. Lancet 353(9160): 1226-1231,1999.
Velazquez FR, Matson DO, Guerrero ML, Shults J, Calva JJ, Morrow AL, Glass RI, Pickering LK, Ruiz-Palacios GM. Serum antibody as a marker of protection against natural rotavirus infection and disease. Journal of Infectious Diseases 182(6): 1602-1609, 2000.
Isaacman DJ, Shults J, Gross TK, Davis PH, Harper M. Predictors of bacteremia in febrile children 3 to 36 months of age. Pediatrics 106(5): 977-982, 2000.
Shults J. Modeling the correlation structure of data that have multiple levels of association. Communications in Statistics: Theory and Methods 29(5-6): 1005-1015, 2000.
Kelly CS, Morrow AL, Shults J, Nakas N, Strope GL, Adelman RD. Outcomes evaluation of a comprehensive intervention program for asthmatic children enrolled in Medicaid. Pediatrics
Karlowicz MG, Giannone PJ, Pestian J, Morrow AL, Shults J. Does candidemia predict threshold retinopathy of prematurity in extremely low birth weight (?1000g) neonates? 105(5):1029-1035, 2000. Pediatrics
Medoff-Cooper B, McGrath JM, Shults J. Feeding Patterns of Full Term and Preterm Infants at Forty Weeks Post-Conceptional Age. 105(5):1036-1040, 2000. Developmental and Behavioral Pediatrics 23(4): 231-236, 2002.
Shults J, Morrow A. Use of quasi-least squares to adjust for two levels of correlation. Biometrics 58:521-530, September, 2002.
Hughes MB, Shults J, McGrath J., Medoff-Cooper B. Temperament characteristics of premature infants in the first year of life. J. Dev. Behav. Pediatr. 23(6): 430-435, 2002.
Keane A, Houldin A, Allison P, Jepson C, Shults J, Nuamah I, Brennan A, Lowery B, McCorkle R. Factors Associated with Distress Over Time in Urban Residential Fire Survivors. Journal of Nursing Scholarship 34(1): 11-17, 2002.
Naik DN, Khattree R, Shults J. A note on likelihood based inference for AR(1) and MA(1) processes under certain robust alternatives to multivariate normality. Journal of Statistical Theory and Applications, 1(1): 57-62, 2002.
Kwiatkowski JL, Hunter JV, Smith-Whitley K, Katz M, Shults J, Ohene-Frempong K. Transcranial Doppler ultrasonography in siblings with sickle cell disease. British Journal of Haematology
Richmond TS, Kauder DK, Hinkle J, Shults J. Early predictors of long-term disability after injury. 121(6): 932-937, 2003. American Journal of Critical Care
Brewer-Smyth K, Wolbert Burgess A, Shults J. Neurologic and Neuroencodrine Correlates of Violent Criminal Behavior of Female Prison Inmates. 12(3): 197-205, 2003. Biological Psychiatry 55(1): 21-31, 2004.
Amsterdam JD, Shults J, Brunswick DJ, Hundert M. Short-Term Fluoxetine monotherapy for bipolar type II or bipolar NOS major depression- low manic switch rate. Bipolar Disorders 6(1): 75-81, 2004.
Lipman TH, Hench KD, Benyi T, Delaune J, Gilluly KA, Johnson L, Johnson MG, McKnight-Menci H, Shorkey D, Shults J, Waite FL, Weber C. A multicentre randomised controlled trial of an intervention to improve the accuracy of linear growth measurement. Archives of Disease in Childhood. 89(4): 342-346, 2004.
Leonard MB, Shults J, Elliott D, Stallings VA, Zemel BS. Interpretation of whole body DXA in the assessment of cortical bone health in children: Validation with peripheral QCT. Bone
Leonard MB, Shults J, Wilson BA, Tershakovec A, Zemel BS. Obesity during childhood and adolescence augments bone mass and bone dimensions. 34(6): 1044-1052, 2004. American Journal of Clinical Nutrition
Leonard MB, Feldman HI, Shults J, Zemel, BS, Foster BJ, Stallings VA. Long-term, high-dose glucocorticoids and bone mineral content in childhood glucocorticoid-sensitive nephritic syndrome. 80(2): 514-523, 2004. New England Journal of Medicine 351(9): 868-875, 2004.
Shults J, Whitt M, Kumanyika S. Analysis of data with multiple sources of correlation in the framework of generalized estimating equations. Statistics in Medicine. 23: 3209-3226, 2004.
Penning T, Shen YM, Mick R, Shults J, Field J. Polycyclic Aromatic Hydrocarbon 0-Quinones Mutate p53 in Human Lung Adenocarcinoma (A549) cells. Polycyclic Aromatic Compounds. 24: 583-596, 2004.
Veronese M.L., Algazy K., Bearn L., Shults J, Eaby B., Alavi J., Evans T., Stevenson J.P. Gefitinib (ZD1839) in Patients with Advanced Non-Small Cell Lung Cancer (NSCLC): the Expanded Access Protocol Experience at the University of Pennsylvania. Cancer Investigation. (in Press).
Foster, B. Shults J, Zemel, B, Leonard, M. Interactions between growth and body composition in children treated with high-dose chronic glucocorticoids. American Journal of Clinical Nutrition. (in press).
Burnham J, Shults J, Semeao E, Foster B, Stallings V., Leonard M., Whole Body Bone Mineral Content in Pediatric Crohn Disease: Dissecting the Effect of Altered Growth, Body Composition, and Pubertal Development. J. Bone Miner. Research (in press).
Weng F, Shults J, Herskovitz RM, Zemel B, Leonard M. Vitamin D Insufficiency in Steroid-Sensitive Nephrotic Syndrome in Remission. Pediatric Nephrology (in press).
Kumanyika SK, Shults J, Fassbender J, Whitt MC, Brake V, Kallan MJ, Iqbal N, Bowman MA. Outpatient Weight Management in African Americans: The Healthy Eating and Lifestyle Program (HELP) Study. Preventive Medicine (in press).
O'Neill K, Shults J, Stallings V, Stettler NJ. Child-feeding practices in children with Down Syndrome and their siblings. Journal of Pediatrics (in press).
