1.
Considerations in bioinformatics
analyses and study design
Elana J Fertig
Johns Hopkins University

2.
Why study design and bioinformatics
pipelines?

3.
Let’s team up to avoid painful power
calculation discussions
• https://www.youtube.com/watch?v=PbODigCZqL8

4.
Is there a boundary between standard
bioinformatics and AI/data science?

5.
Data science and statistics are a continuum
that must work together for best analyses

6.
How does bioinformatics work?

7.
When to contact the bioinformatician?
“To call in the statistician after the experiment is done is no more
than asking him to perform a post-mortem examination: he may
be able to say what the experiment died of.” Ronald Fisher

8.
Why? Am I wasting your time? Never.
Are you really just a control freak? Ok, maybe.
The GIGO principle of computer science:
Garbage In Garbage Out

9.
Best analyses come from good data cleaning
and study design

10.
Considerations for study design
• Sample preparation impacts which technologies you can use
• Biological hypothesis should drive technology selection
• “Off-label” use of technologies impacts technology protocols (e.g.,
TCR sequence, virus, or splice variant detection from bulk or sc RNA-
seq)
• Consider study design to anticipate the impact of technical artifacts
may impact data quality (e.g., library, sequencing run, batch,
technician, date of processing, age of sample, etc).
Measure twice, cut once

11.
Core coordination minimizes off-label analysis costs
Off-labelinformatics
toolsworkonrawdata

12.
Published bladder cancer microarray data set
Leek et al. 2010

13.
Even large consortia datasets like TCGA have
batch effects
Fortin et al., 2014

14.
Design studies to avoid confounding technical
artifacts and biological covariates

15.
Batch effects change the correlation structure
between genes
Leek et al. 2010

16.
Batch effects change the correlation structure
between genes
Leek et al. 2010

17.
Study design and data cleaning are the most
critical part of any analysis

18.
We can mathematically correct for known
batch effects in data with good study designs

19.
We can correct for batch effects if we know
they are there

20.
Recognizing confounded designs
• Trial Arm A in one batch and trial Arm B in another
• Pre-treatment in one batch and post-treatment in another
• Responders in one batch and non-responders in another
• Designs can get complicated. E.g., what do you do if you have
multiple tissue sites from multiple individuals and you want to
compare both site and individual differences?
We love to help
during design!

21.
What should we do?
Leek et al. 2010

22.
Bioinformatics as a team sport and best
practices
• Early consultation for sample
preparation, technology selection,
and study design
• Interactive collaboration during
data preprocessing and cleaning
• Reproducible scripts to include as
manuscript supplements or online
to document analysis steps
• Open source software for
dissemination of any new
algorithms employed in analysis

23.
Summary
• It is never too early to contact your friendly neighborhood
bioinformatician and we can consult on
• Sample preservation
• Technology selection
• Study design
• Analysis plan and preprocessing
• Data parasiting
• Coordinated collaboration in the data generation process and with
the sequencing core minimizes costs and maximizes data quality