Transcript An End to Ulcers? By Kristi Hannam and Rod Hagley

An End to Ulcers?
A Case Study in the Scientific Method
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
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History of the understanding
of stomach function & ailments
HIPPOCRATES
WILLIAM BEAUMONT
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Q1: What do you think causes
ulcers?
A: Stress.
B: Excessive stomach acids.
C: Bacteria.
D: A bad diet and alcohol use.
E: Being overweight.
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What Causes Ulcers?
Design an experiment to test if your hypothesis is true.
In your group, design the experiment. Remember, be
specific about how you would treat your groups and what
you would measure!
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Q2: Which is a good way to test the
“excess acid hypothesis”?
A: Examine ulcer patients of a range of ages and
measure their stomach acid levels.
B: Have volunteers drink alcohol and measure their
stomach acid levels.
C: Lower stomach acid levels of some volunteers (using
drugs/antacids), and measure numbers of ulcers in all
volunteers.
D: Put volunteers through a stress test and then
measure their stomach acid levels.
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Q3: What step in the scientific method
does this test represent?
A: Making observations.
B: Developing a hypothesis.
C: Testing a hypothesis.
D: Getting results.
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A Possible Study Design
 Doctors divide patients into two groups:
Group 1 received antacids and
were instructed to take them
3x/day
Group 2 received sugar pills
and were instructed to take
them 3x/day
 After 3 months, the number of ulcers per patient
is checked.
 Predict what the results would look like if the
excess acid theory was supported.
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# Ulcers/ patient
Draw this graph: Predict what the results would look like if
the “excess acid theory” was supported by the results of
this study:
Group 1
Group 2
Treatment Group
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B
# Ulcers/ patient
A
# Ulcers/ patient
Q4: Which graph most closely matches
the results you predicted?
Group 1
Group 2
Treatment Group
# Ulcers/ patient
C
D
Group 1
Group 2
Treatment Group
# Ulcers/ patient
Group 1
Group 2
Treatment Group
Group 1
Group 2
Treatment Group
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 Patients who took
antacids had
decreased ulcer
symptoms.
 If the patients stopped
taking the antacids
their ulcers returned.
Image by: Midnightcomm
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Dr. J. Robin Warren: (pathologist)
Examines stomach
biopsies of patients
with various stomach
ailments.
Low Power
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Dr. Warren thought he saw:
High Power
 Helicobacter pylori
(a new species of
bacteria)
 But no one else
believed him!
The black squiggly spots on the slide
are bacteria that Dr. Warren observed
In his biopsy slides.
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Q6: Dr. Warren’s colleagues did not believe there
were bacteria in the stomach. Why do you think
other pathologists did not believe bacteria were
in the stomach biopsies?
A: Bacteria are never found inside the human body.
B: The pH of the stomach is too acidic for any
bacteria to survive.
C: No one else had reported seeing bacteria in their
biopsy samples.
D: Ulcers and stomach cancer are caused by age,
stress and diet – bacteria have nothing to do with
the problems the patients came to the hospital for.
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Talk to your neighbor
 Dr. Warren thinks H. pylori causes
ulcers.
 What is another hypothesis to explain
why Dr. Warren was finding bacteria on
his slides? (there are at least three
alternative hypotheses...)
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Alternative explanations
(hypotheses):
1. The biopsy specimens were contaminated
AFTER samples were taken from the patients.
2. The bacteria live in the stomach, but do no
damage.
3. The slides were already contaminated with
bacteria.
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Dr. Barry J. Marshall Joins Dr.
Warren’s Research
 Hypothesis: Bacteria cause stomach ulcers.
 If you were working with Drs. Warren & Marshall to
design a study to determine whether the bacteria
caused ulcers, how would you do it?
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Their First Survey Study:
 100 stomach ulcer patients
surveyed (biopsy taken).
 100% had H. pylori present.
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Q7: The doctors treated ulcer patients with
antibiotics to see if the disease stopped.
What is missing from their study?
A: An experimental treatment.
B: A control group.
C: An independent variable.
D: A dependent variable.
E: A hypothesis.
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Important Aspects of
Experimental Design
 Testable hypothesis, i.e., a way to measure
a response and a way to divide groups up
into:
 Control and Treatment Groups
 Control is group that does not get the hypothesized
treatment.
 Treatment is group that does get the hypothesized
treatment.
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The Importance of Controls
Why do we need controls? Explain to your
neighbor …
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Number of ulcers
after 2 months
If they set up their antibiotic study with a treatment group
receiving antibiotics and a control group receiving a
placebo (no antibiotics), what results would you expect if
the original “excess acid hypothesis” was supported?
Control
Experimental
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C
Con
Exptl
D
Con
Exptl
Number of ulcers
after 2 months
B
Con
Exptl
Number of ulcers
after 2 months
A
Number of ulcers
after 2 months
Number of ulcers
after 2 months
Q8: What results would you expect if the old
“excess acid hypothesis” were supported?
Con
Exptl
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Number of ulcers
after 2 months
What results would you expect if Drs.
Warren and Marshall’s “bacteria cause
ulcers” hypothesis is supported?
Control
Experimental
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Con
A
Con
Number of ulcers
after 2 months
Exptl
Exptl
D
Con
Exptl
Number of ulcers
after 2 months
C
B
Number of ulcers
after 2 months
A
Number of ulcers
after 2 months
Q9: What results would you expect if the old “bacteria
cause ulcers hypothesis” were supported?
Con
Exptl
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Actual Results of Warren & Marshall’s
Study
 When treated with antibiotics, 80% of patients were
permanently cured of their ulcers.
 To further demonstrate the cause and effect
relationship, Dr. Marshall (who did NOT suffer from
ulcers), swallowed a flask of H. pylori from the lab.
 Within a week he was suffering from symptoms of
gastritis and had H. pylori populations in his stomach!
 He cured himself with an antibiotic treatment.
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Q12: If your family member was diagnosed
with stomach ulcers, what do you think the
recommended treatment would be?
A: Lower stress levels.
B: Change diet to eliminate spicy food.
C: Take a course of antibiotics.
D: Drink milk to lower stomach acid levels.
E: Lose weight and exercise.