Biometrics Core


The Biometrics Core provides a central resource of biostatistical expertise to improve the conception, design, and analysis of HIV/AIDS studies.

Any CFAR investigator can consult with Core biostatisticians and quantitative scientists for assistance with study planning and design for grant applications (eg, sample size and power calculations, development of analytical plans), study implementation (eg, data management, statistical analysis), or research communication (eg, drafting of abstracts, posters, or articles).

In addition to collaborating on specific projects with basic, clinical, and scientific researchers, the Core offers training and education in quantitative methods for all CFAR investigators and also provides a multidisciplinary forum for discussion of ideas, trends, and problem-solving tips related to advanced quantitative methods.    


We have found that it is most useful to collaborate with investigators as early as possible during a project, for example even before study aims are finalized.

The Viral Dynamics Primer is intended to introduce the concepts of viral dynamics to researchers who are conducting studies of this type, are analyzing data from studies of this type, or who would like to learn more about research in this area. No experience in mathematics or statistics is assumed. 

The training and mentoring of CFAR investigators, especially those early in their careers, is an important goal of the CFAR Biometrics Core.


The Biometrics Core is collaborating on a range of research projects involving the prevention, pathogenesis, or treatment of HIV/AIDS. Examples include:

  Mathematical Modeling of Viral Dynamics and/or Viral Set Point (Dr Holte)

  • Examination of dynamics of viral RNA and DNA in the female genital tract after the start of therapy, and analysis of viral load trajectories in relation to survival outcomes using functional data analytic techniques (w/ Drs McClelland, Overbaugh, and Graham)
  • Analysis of patterns of viral RNA and DNA in breast milk of HIV-1 infected mothers (w/ Dr John-Stewart)
  • Exploration of the viral dynamics of HIV/Hepatitis C co-infection (w/ Drs Wang and Scott)

 Quantitative Study of Viral Sequences and Viral Reservoirs (Dr Holte, Mr Tapia)

  • Search for potential HIV-1 compartmentalization within the female genital tract, and analysis of HIV-1 genotypes from the uterus, cervix, and blood to clarify dynamics and spread of HIV-1 within the body (w/ Drs Frenkel, Bull, Mitchell, and Wagner)

 Identifying Predictors of Viral Genital/Rectal Shedding During Antiretroviral Treament (Dr Holte, Mr Tapia)

  • Statistical analysis of data from phylogenetic trees, with permutation-based methods, to explore mechanisms associated with discordant shedding (and likely higher risk of transmission) of HIV-1 from the genital tract and rectum (w/ Dr Frenkel)

 Seattle Primary Infection Project (Dr Holte, Ms Yuhas)

  • Management of project database and statistical analysis for the Seattle Primary Infection Program (SeaPIP). The project aims to evaluate the role of immune pressure on evolution of HIV virus, emergence of escape mutations in highly conserved regions, fitness costs due to escape mutations, and the role that viral fitness has in determining viral set point.

 Optimizing Pediatric HIV-1 Therapy Trials (Mr Tapia)

  • Data management and statistical analysis for a study that aims to determine, following early antiretroviral treatment of HIV-infected infants in Kenya to reduce the high risk of mortality in the first two years of life, if subsequent treatment interruptions are possible (w/ Drs John-Stewart and Wamalwa; Optimizing Pediatric HIV-1 Trials)

 Comparing Adherence Interventions in Africa (Mr Tapia)

  • Collaboration on multiple aspects of a factorial randomized trial with the goal of comparing two adherence interventions (counseling vs. alarm device) in terms of both adherence and biological outcomes (w/ Drs Chung, John-Stewart, and Richardson)

 Investigating interactions between the human genital microbiome and syndromes and pathogens (Ms Yuhas)

  • Data management and statistical analysis in support of the STI Cooperative Research Center, including examination of HSV shedding, BV, urethritis, and vaginal and urethral microbiome data

 In addition to research collaborations, the Biometrics Core engages in educational and institutional activities to support multidisciplinary research within the CFAR. These include:

CFAR Award Programs
Each year, Dr Holte provides statistical consultations to various CFAR award programs, including the CFAR Developmental Core New Investigator Awards (NIA) and HIV-Associated Malignancy Research Pilot Awards.

Biostatistics Core for the Seattle Primary Infection Project (PI, James Mullins)
Dr Holte has served as the lead statistician for the Seattle Primary Infection Project since its inception.  She continues to collaborate with the group on a variety of mathematical and statistical activities.


University of Washington, Biostatistics:

Fred Hutch:



Sarah Holte

Sarah Holte, PhD

Core Director
sholte at




Barbra Richardson, PhD
Core Co-Director
barbrar at






Ken Tapia, MS
Core Manager, Biostatistician
ktapia at





Krista Yuhas, MS
yuhask at





Joshua Stern, MS
jstern77 at




Pirie Hart

Pirie Hart, PhD, MBA
Senior Computer Specialist
pirie at



Core Steering Committee: Ann Collier, MD; Thomas Fleming, PhD; Jim Hughes, PhD; Lisa Manhart, MPH, PhD; Scott McClelland, MD; Jennifer Slyker, PhD


We have found that it is most useful to collaborate with investigators as early as possible during a project, for example even before study aims are finalized. Therefore, we encourage you to submit a Request For Consultation, which will be used to help coordinate biostatistical and other quantitative support for manuscripts, abstracts, and meeting presentations.  When submitted, this form will be sent to the Biometrics Core Director (Sarah Holte, sholte at and Core Manager (Ken Tapia, ktapia at
Sarah Holte, PhD
CFAR Biometrics Core Director
Phone: (206) 744-3647(206) 744-3647
E-mail: sholte at