HW1_SOHAIB_KHURAM_09052023
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Virginia Commonwealth University *
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Industrial Engineering
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Dec 6, 2023
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BIOS 500 Homework 1
Name:
Sohaib Khuram
Although you are encouraged to work together in groups, collaboration
does not mean copying a classmate’s response to a question. What you
turn in must represent your understanding of the concepts learned.
1.
Descriptive vs inferential.
Do Problems 1.10 (p. 8) and 1.24 (p. 10)
in the text- book.
(a)
1.
10 is an inferential statistics example since the data is sampled
from a part of the population and is used to estimate a national rate.
(b)
1.
24 is also a problem of descriptive statistics since the rates (death
per 100,00 population) is a way to describe the rates of death by
cause and does not involve any hypothesis testing nor any
generalizations are made.
2.
Observational studies vs intervention studies/experiments.
Do
Problems 1.18 and 1.20 on p. 9.
(a)
1.18 is a case of an observational study as there was no
variable that was controller for by the researchers. They were
merely looking at differences in rate of death amongst left vs
right-handed individuals.
(b)
1.20 is clearly an experimental study design as researchers randomly
assign individuals to different treatment groups of aspirin vs placebo
to test the 10-year incidence rate of a major cardiovascular event
amongst 45+ yr old women.
3.
Choose the correct answer.
(a)
Which is cheaper to conduct:
case-control or prospective cohort?
(b)
Which takes longer to conduct: case-control or
prospective
cohort?
(c)
Which is longitudinal: case-control,
cohort, or both?
(d)
Which requires an intervention: observational study,
clinical
trial, or
both?
(e)
Which requires randomization: cohort, clinical trial,
RCT, or all of
these?
(f)
Which is prospective: case-control,
clinical
trial, or both?
(g)
Which requires that the outcome status is known at the onset of
study:
case-
control, cohort, or both?
(h)
Which is the gold standard for demonstrating efficacy of an
intervention: cohort, clinical trial, or
RCT?
1
4.
Two surgical procedures were compared in a certain prospective
cohort study. The outcome was mortality status (i.e., ‘dead’ or ‘alive’
during the last day of observation). Baseline was set at the date of
surgery. Subject follow-up time differed from subject to subject. The
last follow-up visit for some patients was as short as
1
month; for
some patients it was as long as 3 years. In determining which surgical
procedure had a lower mortality risk, a researcher divided the number
of people who died in each surgical group by the number of people
in that group. Then she compared the two mortality risks by
calculating the ratio of the two risks. What did this researcher fail to
take into account?
(a)
Variable follow-up time means that the ratio of people from each
surgery might be vastly different and data might be censored. So
people with a 1 month follow-up are not contributing the same
data as the 3 year follow-up. So the mortality risk can inaccurately
account for which surgery was better/less risky.
5.
Meinert (1986) lists the requirements of a sound treatment
allocation scheme. Flipping a coin to determine whether a subject
receives the test treatment or the control treatment violates which
requirement?
(a)
Flipping a coin violates multiple requirements that might not
seem consequential. First, while a coin flip is random, it is not
balanced. We can’t ensure each group has a fair sample size.
Secondly, this isn’t a reproducible method and there doesn’t
seem to be any exclusionary criteria. Also, both side know
which group they are in which can lead to concealment issues.
6.
Using the NIH definition of a clinical trial, which of the following
disqualifies the study as a clinical trial? (There may be more than
one answer.)
(a)
A study does not randomize the assignment of treatment to patients.
(b)
A
study
does
not
have
a
comparison
group.
2
(c)
A study uses mice as subjects.
(d)
A
study
does
not
have
an
intervention;
the
study
is
observational.
(e)
A study is cross-sectional.
7.
Cohort studies may be prospective or retrospective. What is the
similarity be- tween prospective and retrospective cohort studies?
What is the difference?
(a)
Both are observational studies, there are groups/cohorts based
on exposure status, data on exposure and outcome status are
collected to better understand the relationship between the
two. Retrospective studies look back in time to those who have
an outcome of interest already and try to connect to different
exposures while a prospective study looks to collect data before
an outcome of interest occurs.
8.
Using PICOT, compare and contrast the two successful studies that
looked at the use of monoclonal antibody cocktail in the treatment
of patients in the early stage of SARS-CoV2 infection:
•
Bamlanivimab+Etesevimab
(
https://www.nejm.org/doi/full/10.1056/NEJMoa2102685
) and
•
Casirivimab+Imdevimab
(
https://www.nejm.org/doi/full/10.1056/NEJMoa2035002
)
Bamlanivimab+Etesevim
ab
Casirivimab+Imdevima
b
P
opulation
Ambulatory patients with
mild or moderate
covid 19 who were at high risk for
progressing to severe disease
275 18+ yr olds, symptomatic, non-
hospitalized patients with covid 19
(outpatients)
I
nterventio
n
Single intravenous infusion of a neutralizing
monoclonal antibody combination agent
(2800 mg of bamlanivimab + 2800 mg
Etesevimab)
Placebo vs 2 different groups for the
neutralizing monoclonal antibody
serums (2.4g or 8 g of REGN-COV2)
C
ompariso
n
Both groups have a lab diagnosis of severe
acute respiratory syndrome coronavirus 2
infection
Both groups had to be outpatients with
no more than 3 days since COVID
positive result and no more than 7 days
since symptom onset before
randomization
O
utcome
Overall clinical status of patients (Covid 19
related hospitalization of death from any
cause by day 29)
Quantitative virologic analysis, COVID
19 serum antibody testing, and
measurement of two component REGN-
COV2 in serum was measured to see if
viral load was any different in the
groups. Specifically, time-weighted
average change in the viral load (in
log10 copies per milliliter) from baseline
(day 1) through day 7
T
ime
September 4 2020 to December 8 2020 was
the enrollment period (3 month period)
From May till September 4
th
was the
interim period for this study that is
published
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9.
During a feverish illness, young children may sometimes have a
febrile convul- sion. Febrile convulsions are very frightening to
parents, but they do not mean that the child is epileptic. They
sometimes recur. Wallace and Smith (1980) car- ried out a study to
see whether treating children with one of two anti-epileptic drugs,
phenobarbitone or valproic acid, would reduce the risk of further
con- vulsions. The subjects in this trial were 121 children who had
had their first convulsions during a feverish illness of 38
◦
or more,
and were consecutive ad- missions to 5 pediatric units. Children
were thought to be at an increased risk of another fit if they were
under 19 months, had an abnormal neurological state, had a family
history of seizures, or the initial convulsion was multiple,
prolonged, or on one side of the body only. Parents of these high-
risk chil-
dren were advised alternatively to give either
phenobarbitone or valproic acid. Low-risk children were prescribed
either phenobarbitone, or valproic acid, or no treatment. Allocation
was sequential.
The researchers do not say why they split the children into high-
and low-risk groups, but a possible reason was that they thought it
unethical not to offer treatment to the children they thought to be
at high risk. We could analyze this study as two separate trials, one
in high-risk and another in low-risk children.
Things started to go wrong. Many parents could not be persuaded
that their child should be given the drugs, even though they were
in the high-risk group. The researchers decided to reclassify the
children into three groups: receiving phenobarbitone (as allocated),
receiving valproic acid (as allocated), or receiv- ing no treatment
(as allocated, or because parents refused). The distinction
between high- and low-risk was abandoned. In other words, the
researchers assumed that those who refused the treatment were
comparable to those who accepted it, and placed the refusals in the
control group. This means that the
researchers could not
distinguish between the effects of the treatment and the effects of
differences in health behavior, etc. between groups. Refusals in
trials usually have a worse prognosis than acceptors, and the
control group might have more fits than the treated groups,
irrespective of treatment. The analysis that the researchers
performed was biased. Why? In this particular case, how does
analysis by intention to treat minimize the bias?
By going with allocation-based assignment as opposed to
randomization or even based on placing subjects based on high/low
risk, we introduce a confounding factor such as having high risk
patients in the placebo group biases the number of convulsions to
be higher in the non-treatment group, thus making it seem like the
treatment is more effective than it actually is. There’s also the bias
that the health behaviors of those who would refuse treatment,
even when considered as high risk and having the most to benefit
from treatment, are different from those who would not refuse
treatment thus making the comparison unfair.
By using Intention to Treat, researchers would randomize subjects
to the groups they originally designed for and analyze them
regardless of whether they followed the treatment. There might be
data loss and other issues to resolve but the researchers wouldn’t
have to deal with the bias introduced with the procedure they
chose to go with.
10.
Did you use artificial intelligence (AI) software to complete this
assignment? If you did, describe how you used the tool and write
the prompts you used to generate results.
(a)
I used AI more like a search engine to get definitions into
specific questions I had. Some specific prompts I used are as
follows:
•
What are some of the differences between clinical trials
and randomized clinical trials
•
NIH definition of a clinical trial
•
List Meinert’s requirements for good treatment
allocation
•
What is considered intention to treat analysis