Transcript B. She is laying the book on the table.

Scientific Writing, HRP 214
Weekly Quiz
Scientific Writing, HRP 214
Weekly Quiz
A. It was a secret among friends.
B. It was a secret between friends.
Scientific Writing, HRP 214
Weekly Quiz
A. It was a secret among friends.
B. It was a secret between friends.
Scientific Writing, HRP 214
Weekly Quiz
A. The close friendship that existed between
them was quickly dissolved.
B. The close friendship that existed among
them was quickly dissolved.
Scientific Writing, HRP 214
Weekly Quiz
A. The close friendship that existed between
them was quickly dissolved.
B. The close friendship that existed among
them was quickly dissolved.
Scientific Writing, HRP 214
Weekly Quiz
A. She eluded to the fight that occurred earlier.
B. She alluded to the the fight that occurred earlier.
Scientific Writing, HRP 214
Weekly Quiz
A. She eluded to the fight that occurred earlier.
B. She alluded to the the fight that occurred
earlier.
Scientific Writing, HRP 214
Weekly Quiz
A. She eluded the fight.
B. She alluded the fight.
Scientific Writing, HRP 214
Weekly Quiz
A. She eluded the fight.
B. She alluded the fight.
Scientific Writing, HRP 214
Weekly Quiz
A. She lies out in the sun.
B. She lays out in the sun.
Scientific Writing, HRP 214
Weekly Quiz
A. She lies out in the sun.
B. She lays out in the sun.
Scientific Writing, HRP 214
Weekly Quiz
A. She is lying out in the sun.
B. She is laying out in the sun.
Scientific Writing, HRP 214
Weekly Quiz
A. She is lying out in the sun.
B. She is laying out in the sun.
Scientific Writing, HRP 214
Weekly Quiz
A. She laid out in the sun yesterday.
B. She lay out in the sun yesterday.
Scientific Writing, HRP 214
Weekly Quiz
A. She laid out in the sun yesterday.
B. She lay out in the sun yesterday.
Scientific Writing, HRP 214
Weekly Quiz
A. She had laid out in the sun too much as a
kid.
B. She had lain out in the sun too much as a
kid.
Scientific Writing, HRP 214
Weekly Quiz
A. She had laid out in the sun too much as a
kid.
B. She had lain out in the sun too much
as a kid.
Scientific Writing, HRP 214
Weekly Quiz
A. She lies the book on the table.
B. She lays the book on the table.
Scientific Writing, HRP 214
Weekly Quiz
A. She lies the book on the table.
B. She lays the book on the table.
Scientific Writing, HRP 214
Weekly Quiz
A. She is lying the book on the table.
B. She is laying the book on the table.
Scientific Writing, HRP 214
Weekly Quiz
A. She is lying the book on the table.
B. She is laying the book on the table.
Scientific Writing, HRP 214
Weekly Quiz
A. She laid the book on the table this
morning.
B. She lay the book on the table this
morning.
Scientific Writing, HRP 214
Weekly Quiz
A. She laid the book on the table this
morning.
B. She lay the book on the table this
morning.
Scientific Writing, HRP 214
Weekly Quiz
A. She had lain the book on the table.
B. She had laid the book on the table.
Scientific Writing, HRP 214
Weekly Quiz
A. She had lain the book on the table.
B. She had laid the book on the table.
Scientific Writing, HRP 214
Weekly Quiz
A. Now I lay down to sleep.
B. Now I lie down to sleep.
Scientific Writing, HRP 214
Weekly Quiz
A. Now I lay down to sleep.
B. Now I lie down to sleep.
Scientific Writing, HRP 214
Weekly Quiz
A. Now I lay me down to sleep.
B. Now I lie me down to sleep.
Scientific Writing, HRP 214
Weekly Quiz
A. Now I lay me down to sleep.
B. Now I lie me down to sleep.
Scientific Writing, HRP 214
Weekly Quiz
A. I am disinterested in your results.
B. I am uninterested in your results.
Scientific Writing, HRP 214
Weekly Quiz
A. I am disinterested in your results.
B. I am uninterested in your results.
Scientific Writing, HRP 214
Weekly Quiz
A. We think you should look into an
alternative career path, i.e. get a new
job.
B. We think you should look into an
alternative career path, e.g. get a new
job.
Scientific Writing, HRP 214
Weekly Quiz
A. We think you should look into an
alternative career path, i.e. get a new
job.
B. We think you should look into an
alternative career path, e.g. get a new
job.
Scientific Writing, HRP 214
Weekly Quiz
A. They prefer mixed drinks, e.g. gin and
tonic or martinis.
B. They prefer mixed drinks, i.e. gin and
tonic or martinis.
Scientific Writing, HRP 214
Weekly Quiz
A. They prefer mixed drinks, e.g. gin and
tonic or martinis.
B. They prefer mixed drinks, i.e. gin and
tonic or martinis.
Scientific Writing, HRP 214
Weekly Quiz
A.
B.
She served as a disinterested party in
the dispute.
She served as an uninterested party in
the dispute.
Scientific Writing, HRP 214
Weekly Quiz
A.
B.
She served as a disinterested party in
the dispute.
She served as an uninterested party in
the dispute.
Scientific Writing, HRP 214
Weekly Quiz
A. You should eat more sweets, e.g.
chocolate.
B. You should eat more sweets, i.e.
chocolate.
Scientific Writing, HRP 214
Weekly Quiz
A. You should eat more sweets, e.g.
chocolate.
B. You should eat more sweets, i.e.
chocolate.
Scientific Writing, HRP 214
Lecture 6: July 27, 2005:
The Abstract, Introduction, and Discussion
Scientific Writing, HRP 214
Abstracts
Abstracts (ab=out, trahere=pull; “to pull out”)






Overview of the main story
Gives highlights from each section of the paper
Limited length (100-300 words, typically)
Stands on its own
Used, with title, for electronic search engines
Most often, the only part people read
Scientific Writing, HRP 214
Abstracts
Gives:
1.
Background
2.
Question asked

Experiment(s) done
3.




6.
Material studied (molecule, cell line, tissue, organ) or the animal or
human population studied
The experimental approach or study design and the independent and
dependent variables
Results found
4.
5.
“We asked whether,” “We hypothesized that,”…etc.
Key results found
Minimal raw data (prefer summaries)
The answer to the question asked
Implication, speculation, or recommendation
Scientific Writing, HRP 214
Abstracts
Abstracts may be structured (with subheadings)
or free-form.
Scientific Writing, HRP 214
Abstracts
Structured example: (The Lancet, May 7, 2003)
Epidemiological determinants of spread of
causal agent of severe acute respiratory
syndrome in Hong Kong
Christl A Donnelly, Azra C Ghani, Gabriel M Leung, Anthony J
Hedley, Christophe Fraser, Steven Riley, Laith J Abu-Raddad, LaiMing Ho, Thuan-Quoc Thach, Patsy Chau, King-Pan Chan, Tai-Hing
Lam, Lai-Yin Tse, Thomas Tsang, Shao-Haei Liu, James H B Kong,
Edith M C Lau, Neil M Ferguson, Roy M Anderson
Scientific Writing, HRP 214
Abstracts
Background
Question
asked
Background
Health authorities worldwide, especially in the Asia Pacific region, are
seeking effective public-health interventions in the continuing epidemic of
severe acute respiratory syndrome (SARS). We assessed the epidemiology of
SARS in Hong Kong.
Methods
We included 1425 cases reported up to April 28, 2003. An integrated
database was constructed from several sources containing information on
epidemiological, demographic, and clinical variables. We estimated the key
epidemiological distributions: infection to onset, onset to admission,
admission to death, and admission to discharge. We measured associations
between the estimated case fatality rate and patients' age and the time from
onset to admission.
“Experiments”
done
Scientific Writing, HRP 214
Abstracts
Results found
Findings
After the initial phase of exponential growth, the rate of confirmed cases fell to less
than 20 per day by April 28. Public-health interventions included encouragement to
report to hospital rapidly after the onset of clinical symptoms, contact tracing for
confirmed and suspected cases, and quarantining, monitoring, and restricting the
travel of contacts. The mean incubation period of the disease is estimated to be 6·4
days (95% CI 5·2-7·7). The mean time from onset of clinical symptoms to admission
to hospital varied between 3 and 5 days, with longer times earlier in the epidemic.
The estimated case fatality rate was 13·2% (9·8-16·8) for patients younger than 60
years and 43·3% (35·2-52·4) for patients aged 60 years or older assuming a
parametric g distribution. A non-parametric method yielded estimates of 6·8% (4·09·6) and 55·0% (45·3-64·7), respectively. Case clusters have played an important
part in the course of the epidemic.
Answer to the question asked
Interpretation
Patients' age was strongly associated with outcome. The time between onset of
symptoms and admission to hospital did not alter outcome, but shorter intervals will
be important to the wider population by restricting the infectious period before
patients are placed in quarantine.
Wider implication
Scientific Writing, HRP 214
Abstracts
Structured example 2:
Binge Eating as a Major Phenotype of Melanocortin 4 Receptor Gene Mutation
New England Journal of Medicine Volume 348:1096-1103 March 20, 2003
Ruth Branson, M.B., Ch.B., Natascha Potoczna, M.D., John G. Kral, M.D.,
Ph.D., Klaus-Ulrich Lentes, Ph.D., Margret R. Hoehe, M.D., Ph.D., and Fritz
F. Horber, M.D.
Scientific Writing, HRP 214
Abstracts
ABSTRACT
Background
Obesity, a multifactorial disease caused by the interaction of genetic factors with the
environment, is largely polygenic. A few mutations in these genes, such as in the
leptin receptor (LEPR) gene and melanocortin 4 receptor (MC4R) gene, have been
identified as causes of monogenic obesity.
Methods
We sequenced the complete MC4R coding region, the region of the
proopiomelanocortin gene (POMC) encoding the melanocyte-stimulating hormone,
and the leptin-binding domain of LEPR in 469 severely obese white subjects (370
women and 99 men; mean [±SE] age, 41.0±0.5 years; body-mass index [the weight in
kilograms divided by the square of the height in meters], 44.1±2.0). Fifteen women
and 10 men without a history of dieting or a family history of obesity served as
normal-weight controls (age, 47.7±2.0 years; body-mass index, 21.6±0.4). Detailed
phenotypic data, including information on body fat, resting energy expenditure, dietinduced thermogenesis, serum concentrations of leptin, and eating behavior, were
collected.
Scientific Writing, HRP 214
Abstracts
Results
Twenty-four obese subjects (5.1 percent) and one control subject (4 percent) had
MC4R mutations, including five novel variants. Twenty of the 24 obese subjects with
an MC4R mutation were matched for age, sex, and body-mass index with 120 of the
445 obese subjects without an MC4R mutation. All mutation carriers reported binge
eating, as compared with 14.2 percent of obese subjects without mutations (P<0.001)
and 0 percent of the normal-weight subjects without mutations. The prevalence of
binge eating was similar among carriers of mutations in the leptin-binding domain of
LEPR and noncarriers. No mutations were found in the region of POMC encoding
melanocyte-stimulating hormone.
Conclusions
Binge eating is a major phenotypic characteristic of subjects with a mutation in
MC4R, a candidate gene for the control of eating behavior.
Scientific Writing, HRP 214
Abstracts
Even more subheadings…
Lung Cancer Screening With Helical
Computed Tomography in Older Adult
Smokers A Decision and Costeffectiveness Analysis
Parthiv J. Mahadevia, MD, MPH; Lee A. Fleisher, MD; Kevin D. Frick,
PhD; John Eng, MD; Steven N. Goodman, MD, PhD; Neil R. Powe,
MD, MPH, MBA
JAMA. 2003;289:313-322.
Scientific Writing, HRP 214
Abstracts
Context
Encouraged by direct-to-consumer marketing, smokers and
their physicians are contemplating lung cancer screening with a
promising but unproven imaging procedure, helical computed
tomography (CT).
Objective
To estimate the potential benefits, harms, and costeffectiveness of lung cancer screening with helical CT in various
efficacy scenarios.
Design, Setting, and Population
Using a computer-simulated model, we compared annual helical
CT screening to no screening for hypothetical cohorts of
100 000 current, quitting, and former heavy smokers, aged 60
years, of whom 55% were men. We simulated efficacy by
changing the clinical stage distribution of lung cancers so that
the screened group would have fewer advanced-stage cancers
and more localized-stage cancers than the nonscreened group
(ie, a stage shift). Our model incorporated known biases in
screening programs such as lead time, length, and
overdiagnosis bias.
Scientific Writing, HRP 214
Abstracts
Main Outcome Measures
We measured the benefits of screening by comparing the absolute and
relative difference in lung cancer–specific deaths. We measured harms
by the number of false-positive invasive tests or surgeries per 100 000
and incremental cost-effectiveness in US dollars per quality-adjusted
life-year (QALY) gained.
Results
Over a 20-year period, assuming a 50% stage shift, the current heavy
smoker cohort had 553 fewer lung cancer deaths (13% lung cancer–
specific mortality reduction) and 1186 false-positive invasive
procedures per 100 000 persons. The incremental cost-effectiveness for
current smokers was $116 300 per QALY gained. For quitting and
former smokers, the incremental cost-effectiveness was $558 600 and
$2 322 700 per QALY gained, respectively. Other than the degree of
stage shift, the most influential parameters were adherence to
screening, degree of length or overdiagnosis bias in the first year of
screening, quality of life of persons with screen-detected localized lung
cancers, cost of helical CT, and anxiety about indeterminate nodule
diagnoses. In 1-way sensitivity analyses, none of these parameters was
sufficient to make screening highly cost-effective for any of the cohorts.
In multiway sensitivity analyses, a program screening current smokers
was $42 500 per QALY gained if extremely favorable estimates were
used for all of the influential parameters simultaneously.
Scientific Writing, HRP 214
Abstracts
Conclusion
Even if efficacy is eventually proven, screening must
overcome multiple additional barriers to be highly costeffective. Given the current uncertainty of benefits, the
harms from invasive testing, and the high costs
associated with screening, direct-to-consumer marketing
of helical CT is not advisable.
Scientific Writing, HRP 214
Abstracts
Science Volume 300, Number 5620, 2 May 2003, pp. 786-789.
The Potential for Earthquake Early Warning in Southern California
Richard M. Allen1* and Hiroo Kanamori2
Earthquake mitigation efforts in the United States currently use long-term probabilistic
hazard assessments and rapid post-earthquake notification to reduce the potential damage
of earthquakes. Here we present the seismological design for and demonstrate the
feasibility of a short-term hazard warning system. Using data from past earthquakes, we
show that our Earthquake Alarm System (ElarmS) could, with current TriNet
instrumentation, issue a warning a few to tens of seconds ahead of damaging ground
motion. The system uses the frequency content of the P-wave arrival to determine
earthquake magnitude, an approach that allows magnitude determination before any
damaging ground motion occurs.
Scientific Writing, HRP 214
Introduction and Background
Introduction and Background Section
Scientific Writing, HRP 214
Introduction and Background
The Literature Search

Utilize online databases, such as MEDLINE, PubMed, and
Ovid.

Have a search strategy.

Have an organizational system!
Scientific Writing, HRP 214
Introduction and Background
The Literature Review

Summarize the current state of knowledge in the area of investigation.

You may have to return to the literature once your results are in hand.







Assume your reader is knowledgeable about the field.
Do not provide an exhaustive historical review.
Avoid nonessential details.
Summarize previous results and conclusions, but do not give the
methods that generated these findings unless they are relevant to your
research question (i.e., your experiment addresses a specific
methodologic limitation of previous experiments)
Refer the reader to general surveys or reviews of the topic if available.
Cite references that reflect the key work that led to your research
question.
Limit the number of references.
Scientific Writing, HRP 214
In writing the literature review, summarize
rather than listing every possible reference
and example.
Scientific Writing, HRP 214
Introduction and Background
Introduction and Background
1. What’s known
2. What’s unknown

Critical literature review
limitations and gaps in previous studies
3. Your burning question
4. Your experimental approach
5. Why your experimental approach is new and different
and important
Scientific Writing, HRP 214
Introduction
Tell a story:

Write it in plain English, not tech-speak.

Take the reader step by step from what is known to
what is unknown. End with your specific question.
(KnownUnknownQuestion)

Emphasize what is new and important about your
work.

Do not state the answer to the research question.

Do not include results or implications.
Introduction

Overweight, Obesity, and Mortality from Cancer in a
Prospectively Studied Cohort of U.S. Adults
Eugenia E. Calle, Ph.D., Carmen Rodriguez, M.D., M.P.H., Kimberly
Walker-Thurmond, B.A., and Michael J. Thun, M.D.
What’s
What’sknown
known
What’s
What’sunknown
unknown
The relations between excess body weight and mortality, not only from all
causes but also from cardiovascular disease, are well established.1,2,3,4,5,6
Although we have known for some time that excess weight is also an important
factor in death from cancer,7 our knowledge of the magnitude of the relation, both
for all cancers and for cancers at individual sites, and the public health effect of
excess weight in terms of total mortality from cancer is limited. Previous studies
have consistently shown associations between adiposity and increased risk of
cancers of the endometrium, kidney, gallbladder (in women), breast (in
postmenopausal women), and colon (particularly in men).8,9,10,11,12
Adenocarcinoma of the esophagus has been linked to obesity.11,13,14 Data on
cancers of the pancreas, prostate, liver, cervix, and ovary and on hematopoietic
cancers are scarce or inconsistent.7,8,9,10,11,15,16,17 The lack of consistency may be
attributable to the limited number of studies (especially those with prospective
cohorts), the limited range and variable categorization of overweight and obesity
among studies, bias introduced by reverse causality with respect to smokingrelated cancers, and possibly real differences between the effects of overweight
and obesity on the incidence of cancer and on the rates of death from some
cancers.18,19
We conducted a prospective investigation in a large cohort of U.S. men and
women to determine the relations between body-mass index (the weight in
kilograms divided by the square of the height in meters) and the risk of death
from cancer at specific sites. This cohort has been used previously to examine
the association of body-mass index and death from any cause.5
“This study will
answer the
question with
better methods.”
Gaps/limitations of
previous studies
Gaps in
The lit.
previous
research
Scientificreview
Writing,
HRP 214
What’s
unknown/the
research
question
What’s
known
Exogenous estrogens prevent or substantially
retard the decrease in bone
Introduction
mineral density (BMD) that accompanies menopause [1]. However, it is unclear
whether exogenous estrogens, administered as oral contraceptives (OCs), can
modify premenopausal BMD. Several studies suggest that exposure to OCs
during the premenopausal years has a favorable effect on BMD [2-10], whereas
other studies show no effect [11-18].
Past studies of the relationship between OC use and BMD have several
limitations. Studies have focused primarily on crude measures of OC use, such
as current, pastThis
and never.
These categories combine diverse types of OC use
study
and may reduce the power to detect an effect. Many studies also failed to take
into account lifestyle characteristics of study participants. Finally, few studies
have considered an effect of OCs on BMD in women of races other than white.
The aim of this study was to evaluate the associations of OCs with spine, hip
and whole body BMD in black and white premenopausal women. Our primary
hypothesis was that there would be an association between cumulative exposure
to estrogen from OCs and BMD.
Scientific Writing, HRP 214
Neurohumoral Features of Myocardial
Stunning Due to Sudden Emotional Stress
Ilan S. Wittstein, M.D., David R. Thiemann, M.D., Joao A.C. Lima, M.D., Kenneth L.
Baughman, M.D., Steven P. Schulman, M.D., Gary Gerstenblith, M.D., Katherine C. Wu,
M.D., Jeffrey J. Rade, M.D., Trinity J. Bivalacqua, M.D., Ph.D., and Hunter C. Champion,
M.D., Ph.D. T
New Engl J Med Volume 352:539-548; Feb 10, 2005.
Scientific Writing, HRP 214
Background/
The lit.
relevance
The potentially
lethal
consequences
of
emotional
review
stress are deeply rooted in folk wisdom, as reflected
by phrases such as "scared to death" and "a broken
heart." In the past decade, cardiac contractile
abnormalities and heart failure have been reported
after acute emotional stress,1,2,3,4,5,6 but the
This study remains unknown. We evaluated 19
mechanism
What’s
patients with "stress cardiomyopathy,"
a syndrome of
unknownby acute
profound myocardial stunning precipitated
emotional stress, in an effort to identify the clinical
features that distinguish this syndrome from acute
myocardial infarction and the cause of transient
stress-induced myocardial dysfunction.
Introduction: cost-effectiveness
study
Cost-Effectiveness of Screening for HIV
in the Era of Highly Active Antiretroviral
Therapy
Gillian D. Sanders, Ph.D., Ahmed M. Bayoumi, M.D., Vandana Sundaram, M.P.H., S.
Pinar Bilir, A.B., Christopher P. Neukermans, A.B., Chara E. Rydzak, B.A., Lena R.
Douglass, B.S., Laura C. Lazzeroni, Ph.D., Mark Holodniy, M.D., and Douglas K.
Owens, M.D.
New Engl J Med Volume 352: 570-585; Feb 10, 2005.
Introduction
Timely identification of human immunodeficiency virus (HIV) infection is
critical from both clinical and public health perspectives. A delay in diagnosis
until late in the course of HIV infection may be associated with irreversible
immunologic damage and related complications. Early identification also
provides the opportunity to reduce transmission of HIV through changes in risk
behavior.1,2,3 Treatment with highly active antiretroviral therapy (HAART) most
likely reduces infectivity4 and may therefore afford an additional public health
benefit by further reducing transmission. Despite these compelling reasons for
early identification, the Centers for Disease Control and Prevention (CDC)
estimate that up to 20,000 new HIV infections annually can be attributed to
people who are unaware of their HIV-positive status. Such people represent up to
280,000 of the approximately 950,000 people infected with HIV in the United
States.5 CDC data indicate that in 41 percent of HIV-positive patients, the
acquired immunodeficiency syndrome (AIDS) develops within a year after they
received the diagnosis,6 suggesting that opportunities for preventing adverse
outcomes were missed.
Background/relevance: what’s known about the
potential merits of screening and early detection
Introduction, continued

Limitations of previous research.
A fundamental strategy of a new CDC initiative to promote
early identification of HIV disease is to make voluntary HIV
testing a routine part of medical care.7,8 Although we and
others previously evaluated the cost-effectiveness of
screening,9,10,11,12 these analyses were performed before
HAART became available. Because both the costs and the
benefits of screening have changed since these analyses were
published, the
current
cost-effectiveness of screening and the
This
study
settings in which screening is economically attractive remain
uncertain. We sought to evaluate the cost-effectiveness of
voluntary HIV screening in health care settings and to assess
how incorporating the costs and benefits associated with
reductions in HIV transmission would influence the costeffectiveness of a screening program.
Introduction: systematic review
Effectiveness of speed cameras in
preventing road traffic collisions and related
casualties: systematic review
Paul Pilkington, lecturer in public health1, Sanjay Kinra, lecturer
in epidemiology and public health medicine2 1 University of the
West of England, Faculty of Health and Social Care, Bristol
BS16 1DD, 2 Department of Social Medicine, University of
Bristol, Bristol .
BMJ Feb. 10, 2005
Statement of problem. What’s known.
Road traffic collisions are an important cause of death and disability worldwide.
Every year around the world 1.2 million people are killed and up to 50 million are
injured or disabled as a result of road traffic collisions.1 Morbidity from road traffic
collisions is expected to increase in future years, and it is estimated that road traffic
collisions will move from ninth to third place in the global burden of disease
ranking, as measured in disability adjusted life years.2 3
Measures to reduce traffic speed are considered essential to reducing casualties on
the road.1 4 5 Speed cameras are increasingly used to help to reduce traffic speeds in
the What’s
belief that unknown/controversial.
this will reduce road traffic collisions and casualties, and an
expansion in the use of speed cameras is under way in many countries, most notably
the United Kingdom.6 The use of speed cameras is controversial, however.
Vociferous opponents, including some motoring associated organisations, oppose
their use, and cameras are often criticised in the media.7-9 The lack of readily
available evidence of the effectiveness of cameras has made it difficult for road
safety and
health professionals
to engageresearch.
in an informed debate about the
Limitations
of previous
effectiveness of speed cameras.
A previous
review
of six
studies found
a 17% reduction in
Whatsmall
wenon-systematic
did to answer
this
question
better.
collisions after introduction of speed cameras.10 Non-systematic reviews can,
however, be limited by bias. We aimed, therefore, to systematically assess the
evidence for the effectiveness of speed cameras in reducing road traffic collisions
and related casualties.
Scientific Writing, HRP 214
Introduction and Background
Introduction and Background
1. What’s known
2. What’s unknown

Critical literature review
limitations and gaps in previous studies
3. Your burning question
4. Your experimental approach
5. Why your experimental approach is new and different
and important
Scientific Writing, HRP 214
Introduction
Tell a story:

Write it in plain English, not tech-speak.

Take the reader step by step from what is known to
what is unknown. End with your specific question.
(KnownUnknownQuestion)

Emphasize what is new and important about your
work.

Do not state the answer to the research question.

Do not include results or implications.
Scientific Writing, HRP 214
THE DISCUSSION
The Discussion is the section that…
•
•
•
Gives you the most freedom
Gives you the most chance to put good
writing on display
Is the most challenging to write
Scientific Writing, HRP 214
The Discussion
Follow your rules for good writing!
Scientific Writing, HRP 214
The Discussion
The purpose of the discussion:
•
•
•
•
Answer the question posed in the Introduction
Support your conclusion with details (yours, others)
Defend your conclusion (acknowledge limits)
Highlight the broader implications of the work
i.e., What do my results mean and why should anyone
care?
Framework of the Discussion
QUESTION TO ADDRESS
CONTENT
What’s the central
finding?
Restate the finding.
Place in the context of other work.
Clearly state what’s new.
Could it be wrong?
Identify and deal with threats to validity. Consider alternative
explanations for your findings given the study design (for clinical or
epidemiologic studies):
BEFORE/AFTER
Temporal trend
Regression to the mean
Selection bias
What does it mean?
OBSERVATIONAL
RANDOMIZED
TRIAL
Loss to follow-up
Low response rate
Recall bias
Unmeasured confounding
Inadequate blinding
Ascertainment bias
Loss to follow-up
Put your work in perspective. Assess its generalizability, and speculate
about its implications.
Suggest mechanisms.
Specify what you think should happen next.
Table 2, Adapted From: Welch HG. Preparing Manuscripts for Submission to Medical
Journals: The Paper Trail. Effective Clinical Practice. 1999; 2: 131-137.
Scientific Writing, HRP 214
The Discussion
The introduction moves from general to specific.
The discussion moves from specific to general.
Scientific Writing, HRP 214
The Discussion
Elements of the typical discussion section…
Key finding (answer to the question(s) asked in Intro.)
1.
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•
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Key secondary findings
Context
2.
3.
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•
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Compare your results with other people’s results
Compare your results with existing paradigms
Explain unexpected or surprising findings
Strengths and limitations
What’s next
4.
5.
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Recommended confirmatory studies (“needs to be confirmed”)
Unanswered questions
Future directions
The “so what?”: implicate, speculate, recommend
6.
•
7.
Supporting explanation, details (lines of evidence)
Possible mechanisms or pathways
Is this finding novel?
Clinical implications of basic science findings
Strong conclusion (kicker!)
EXAMPLE: Samaha FF, Iqbal N, Seshadri P, et al. A
low-carbohydrate as compared with a low-fat diet in
severe obesity. N Engl J Med 2003;348:2074-2081.
INTRODUCTION
The differences in health benefits between a carbohydraterestricted diet and a calorie- and fat-restricted diet are of
considerable public interest. However, there is concern that a
carbohydrate-restricted diet will adversely affect serum lipid
concentrations.1 Previous studies demonstrating that healthy
volunteers following a low-carbohydrate diet can lose weight have
involved few subjects, and few used a comparison group that
followed consensus guidelines for weight loss.2,3 The reported
effects of a carbohydrate-restricted diet on risk factors for
atherosclerosis have varied.2,3,4 We performed a study
designed to test the hypothesis that severely obese subjects
with a high prevalence of diabetes or the metabolic
syndrome [a] would have a greater weight loss, [b] without
detrimental effects on risk factors for atherosclerosis, while
on a carbohydrate-restricted (low-carbohydrate) diet than on
a calorie- and fat-restricted (low-fat) diet.
Scientific Writing, HRP 214
The Discussion
1. We found that severely obese subjects with a high
prevalence of diabetes and the metabolic syndrome lost
more weight in a six-month period on a carbohydraterestricted diet than on a fat- and calorie-restricted diet.
[answer to a] The greater weight loss in the lowcarbohydrate group suggests a greater reduction in
overall caloric intake, rather than a direct effect of
macronutrient composition. [mechanisms] However, the
explanation for this difference is not clear. Subjects in this
group may have experienced greater satiety on a diet
with liberal proportions of protein and fat. However, other
potential explanations include the simplicity of the diet
and improved compliance related to the novelty of the
diet. [possible mechanisms/unanswered questions]
Scientific Writing, HRP 214
The Discussion
2. Subjects in the low-carbohydrate group had greater decreases in triglyceride
levels than did subjects in the low-fat group; nondiabetic subjects on the lowcarbohydrate diet had greater increases in insulin sensitivity, and subjects with
diabetes on this diet had a greater improvement in glycemic control. No adverse
effects on other serum lipid levels were observed. [answer to b] Most
studies suggest that lowering triglyceride levels has an overall cardiovascular
benefit.14,15,16 Insulin resistance promotes such atherosclerotic processes as
inflammation,17 decreased size of low-density lipoprotein particles,18 and
endothelial dysfunction.19 Impaired glycemic control in subjects with other
features of the metabolic syndrome markedly increases the risk of coronary
artery disease.20 As expected, we found that the amount of weight lost had a
significant effect on the degree of improvement in these metabolic factors.
[comparison to previous studies and paradigms] However,
even after adjustment for the differences in weight loss between the groups,
assignment to the low-carbohydrate diet predicted greater improvements in
triglyceride levels and insulin sensitivity. [unexpected] Subjects who lost
more than 5 percent of their base-line weight on a carbohydrate-restricted diet
had greater decreases in triglyceride levels than those who lost a similar
amount of weight while following a calorie- and fat-restricted diet.
[supporting details]
Scientific Writing, HRP 214
The Discussion
3. There was a consistent trend across weight-loss strata toward
a greater increase in insulin sensitivity in the low-carbohydrate
group, although these changes were small and were not
significant within each stratum. [supporting details:
dose/response] Although greater weight loss could not entirely
account for the greater decrease in triglyceride levels and
increase in insulin sensitivity in the low-carbohydrate group, we
cannot definitively conclude that carbohydrate restriction alone
accounted for this independent effect. [mechanisms] Other
uncontrolled variables, such as the types of carbohydrates
selected (e.g., the proportion of complex carbohydrates or the
ratio of carbohydrate to fiber), or other unknown variables may
have contributed to this effect. In addition, more precise
measurements of insulin sensitivity than we used would be
needed to confirm this effect of a carbohydrate-restricted diet.
[limitations/future studies]
Scientific Writing, HRP 214
The Discussion
4. Many of our subjects were taking lipid-lowering
medications and hypoglycemic agents. Although
enrolling these subjects introduced confounding
variables, it allowed the inclusion of subjects with the
obesity-related medical disorders typically
encountered in clinical practice. Analyses from which
these subjects were excluded still revealed greater
improvements in insulin sensitivity and triglyceride
levels on a carbohydrate-restricted diet than on a fatand calorie-restricted diet. [limitations and how they
were addressed]
Scientific Writing, HRP 214
The Discussion
5. Our study included a high proportion of black subjects,
a group previously underrepresented in lifestylemodification studies. [strength] As compared with the
white subjects, the black subjects had a smaller
overall weight loss. Future studies should explore
whether greater weight loss in this population can be
achieved by more effective incorporation of culturally
sensitive dietary counseling. [future directions]
6. The high dropout rate in our study occurred very early
and affected our findings. The very early dropout of
these subjects may indicate that attrition most closely
reflected base-line motivation to lose weight, rather
than a response to the dietary intervention itself.
[limitation]
Scientific Writing, HRP 214
The Discussion
7. Taken together, our findings demonstrate that severely obese subjects with
a high prevalence of diabetes and the metabolic syndrome lost more weight
during six months on a carbohydrate-restricted diet than on a calorie- and fatrestricted diet. The carbohydrate-restricted diet led to greater improvements in
insulin sensitivity that were independent of weight loss and a greater
reduction in triglyceride levels in subjects who lost more than 5 percent of
their base-line weight. [conclusion; restate answers to a and b] These
findings must be interpreted with caution, however, since the magnitude of the
overall weight loss relative to our subjects' severe obesity was small, and it is
unclear whether these benefits of a carbohydrate-restricted diet extend
beyond six months. Furthermore, the high dropout rate and the small overall
weight loss demonstrate that dietary adherence was relatively low in both diet
groups. [big picture] This study proves a principle and does not provide
clinical guidance; given the known benefits of fat restriction, future
studies evaluating long-term cardiovascular outcomes are needed
before a carbohydrate-restricted diet can be endorsed. [take-home
message]
Scientific Writing, HRP 214
The Discussion
Things to avoid in the discussion:
•
Do not simply repeat what is in the Results
•
Do not try to explain every minor flaw
•
Do not attempt to explain away every
unexpected result
•
Do not exaggerate or make extravagant
claims
•
Don’t hedge
Scientific Writing, HRP 214
The Discussion: verb tense
Verb Tenses (active!):
Past, when referring to study details, results, analyses,
and background research:
•
We found that
•
They lost more weight than
•
Subjects may have experienced
•
Miller et al. found
Present, when talking about what the data suggest …
The greater weight loss suggests
The explanation for this difference is not clear.
Potential explanations include
Scientific Writing, HRP 214
The Discussion
Example 2:
Nature 423, 409 - 414 (2003); doi:10.1038/nature01593
The HSC (Haematopoietic stem cells) has the ability to perpetuate
itself as well as to differentiate into mature blood cells of all lineages. In
the mouse, long-term self-renewing HSCs make up approximately
0.007% of bone marrow and can be isolated by their expression of
undetectable levels of lineage markers (such as B220, CD3, Mac-1),
high levels of c-Kit and Sca-1, and low levels of Thy-1 (refs 1, 2).
Although HSCs have been purified successfully and their
phenotypic and functional properties well characterized1-4, a
fundamental question that remains is how their self-renewing
growth is regulated. On the basis of a screen of genes expressed in
HSCs—where we noted that members of the LEF-1/TCF family were
expressed (K. Li, S. Cheshier and I.L.W., unpublished data)—and our
previous finding that Wnt signalling can influence lymphocyte progenitor
cell proliferation5, we have investigated whether Wnt
Scientific Writing, HRP 214
The Discussion
Example 2:
Nature 423, 409 - 414 (2003); doi:10.1038/nature01593
The HSC (Haematopoietic stem cells) has the ability to perpetuate
itself as well as to differentiate into mature blood cells of all lineages. In
the mouse, long-term self-renewing HSCs make up approximately
0.007% of bone marrow and can be isolated by their expression of
undetectable levels of lineage markers (such as B220, CD3, Mac-1),
high levels of c-Kit and Sca-1, and low levels of Thy-1 (refs 1, 2).
Although HSCs have been purified successfully and their
phenotypic and functional properties well characterized1-4, a
fundamental question that remains is how their self-renewing
growth is regulated. On the basis of a screen of genes expressed in
HSCs—where we noted that members of the LEF-1/TCF family were
expressed (K. Li, S. Cheshier and I.L.W., unpublished data)—and our
previous finding that Wnt signalling can influence lymphocyte progenitor
cell proliferation5, we have investigated whether Wnt
Discussion
Our study shows that components of the Wnt signalling pathway can
induce proliferation of purified KTLS bone marrow HSCs while
significantly inhibiting their differentiation, thereby resulting in
functional self-renewal. [ANSWER TO THE QUESTION ASKED]
We find that expression of -catenin in HSCs results in increased growth
with significantly reduced differentiation in vitro for a period of at least
many weeks. HSCs transduced with -catenin give rise to sustained
reconstitution of myeloid and lymphoid lineages in vivo, when
transplanted in limiting numbers. We also find that Wnt signalling is
required for the growth response of normal HSCs to other cytokines, as
overexpression of axin leads to reduced stem cell growth both in vitro
and in vivo. Furthermore, the inhibition of HSC growth with frizzledCRD and the finding that Wnt3a causes expansion of HSCs supports the
interpretation that the effects of -catenin and axin reflect upstream Wnt
activity. Finally, studies with HSCs containing a LEF-1/TCF reporter
indicate that HSCs in vivo respond to endogenous Wnt stimulation. The
expression of a number of Wnt proteins in the bone marrow5 and
frizzled receptors in bone-marrow-derived progenitors and HSCs
supports this possibility22. [line of evidence to support the answer]
Most growth factors that act on HSCs in culture induce no or
limited expansion23 or are unable to prevent differentiation8, 24.
[Context] Thus, one of the most notable findings of our work is
the induction of proliferation and the prevention of HSC
differentiation by the Wnt signalling pathway. [Unexpected
finding] Other signals that increase proliferation of HSCs include
Notch20 and sonic hedgehog25. Moreover, the cyclin-dependent
kinase inhibitor p21Cip1/Waf1 (ref. 26) and the transcription factor
HoxB4 (ref. 21) have been shown to be involved in regulating selfrenewal of HSCs. Notably, Wnt signalling has been shown to
interact with many of these pathways in a variety of organisms27-30,
[Context] and our data show that both HoxB4 and Notch1 are
upregulated in response to Wnt signalling in HSCs. This raises the
possibility that the effects of Wnt signalling on HSCs are mediated
through HoxB4 and/or Notch1 [Speculation] . Whereas HoxB4
could act directly on these HSCs as demonstrated previously21,
Notch1 action would require nearby Notch1 ligands. [possible
pathways]
`
The ability of Wnt3a to induce expansion of HSCs is consistent
with previous studies showing increased numbers of
haematopoietic progenitors from mouse fetal liver and human
bone marrow cells stimulated with Wnt-containing supernatants31,
32. [Context/comparison with previous studies] These studies,
although consistent with ours, are more difficult to interpret as
they did not use purified HSCs, lacked in vivo reconstitution
analysis, and did not provide evidence of a physiological
requirement for Wnt signalling for HSCs. [Gaps in previous
studies] Components of the Wnt pathway have also been shown to
promote proliferation of primitive cells in the skin33, 34, the gut35, 36
and the brain37, and to inhibit differentiation to a variety of
lineages in embryonic stem cells38, raising the possibility that Wnt
signalling may be used as a general cue for self-renewal in stem
and/or progenitor cells from diverse tissues. [Context/big picture]
Its role as a self-renewal signal does not, however, preclude its
involvement in differentiation of stem cells in certain contexts39.
Our findings may have important implications for human
haematopoietic cell transplantation. [the “so what?”: clinical
implication] We have found that soluble Wnt3a protein induces
proliferation of highly purified human bone marrow HSCs in the
absence of any other growth factor (T.R., T. Miyamoto and I.L.W.,
unpublished observation). Induction of HSC growth by Wnt
signalling may allow in vitro expansion of a patient's own or an
allogeneic donor's HSCs, and could provide an increased source of
cells for future transplantation. [clinical implication] Finally, we
have previously raised the hypothesis that self-renewal is a
property that could be dangerous, as an adequate definition of
cancer stem cells is poorly regulated self-renewal of a particular
stage of a developmental lineage40. The demonstration here that
the Wnt/ -catenin pathway may have a role in haematopoietic stem
cell self-renewal leads us to propose that this pathway should be
studied for a role in self-renewal of cancer stem cells. [kicker—
one step broader, applications to cancer]
Scientific Writing, HRP 214
Discussion
The Discussion:
The answer to the key question asked
What’s new
The context
1.
2.
3.
•
4.
5.
6.
7.
How your results fit into, contradict, or add to what’s known or believed
Strengths and limits of the study
The “so what?”: implicate, speculate, recommend
Overall conclusion
Powerful finish
Scientific Writing, HRP 214
Top 5
Scientific Writing, HRP 214
1. Peremptory v. preemptive
Peremptory = cannot be denied
Preemptive = action is one taken before an
adversary can act
He issued a peremptory order.
He ordered a preemptive war in Iraq.
Scientific Writing, HRP 214
2. Subject v. patient
A subject is a volunteer.
A patient is under treatment by a doctor.
The subjects in our study took a quiz about love.
The patients in our study were being treated for
their stomach conditions.
Scientific Writing, HRP 214
3. Strata v. stratum
“Strata” is plural.
“Stratum” is singular.
We analyzed the data, adjusting for the different
age strata.
I was only interested in the association in the
stratum of elderly subjects.
Scientific Writing, HRP 214
4. Averse v. adverse
Averse means “opposed” and usually describes a
person’s attitude.
Adverse means “hostile, unfavorable, opposed”
but usually applies to situations, conditions, or
events—not people.
The bad weather has an adverse effect on my car.
I would not be averse to trying that new restaurant.
Scientific Writing, HRP 214
5. Historic v. historical
Historic means notable in history.
--indicates that it in some way changed the
course of human events
Historical means relating to history or past events.
--not necessarily historic
The signing of the Declaration of Independence
was a historic moment in American history.
Professor Smith gave a historical lecture on the
evolution of toothpicks.
Scientific Writing, HRP 214
Homework for next time…
Assignments for Next Week
 
Read chapter 3 of Successful Scientific Writing
Write intro/background using what you learned in this
week’s lecture.
Email intro/background to me by class Wednesday
August 3rd.
Conferences next week: 4th-5th (schedule posted; email
me to reserve time slot)
Scientific Writing, HRP 214
For next week
Next time…
Materials and Methods, Results, Figures
and Tables…