STAT 602 – Assignment #2 – One and Two Population Inference (72 pts.)
Due 2/3/15
Description of Right Heart Catheterization Study Dataset
These data come from the paper:
The effectiveness of right heart catheterization in the initial care of critically ill patients.
SUPPORT Investigators by Connors AF, et al. published in the Journal of American
Medical Association (JAMA), 1996.
From the abstract of the paper:
OBJECTIVE: To examine the association between the use of right heart catheterization
(RHC) during the first 24 hours of care in the intensive care unit (ICU) and subsequent
survival, length of stay, intensity of care, and cost of care. DESIGN: Prospective cohort
study. SETTING: Five US teaching hospitals between 1989 and 1994. SUBJECTS: A
total of 5735 critically ill adult patients receiving care in an ICU for 1 of 9 pre-specified
disease categories. MAIN OUTCOME MEASURES: Survival time, cost of care,
intensity of care, and length of stay in the ICU and hospital, determined from the clinical
record and from the National Death Index.
RESULTS: The researchers found that patients who had a right heart catheter (SwanGanz line) put in had a 24% higher risk of 30-day mortality than patients that did not
have the procedure performed (i.e. RR = 1.24).
Comments:
However, given that this procedure is generally used when doctors are in some sense
perplexed about what course of treatment to follow, one could argue that this result is
expected because patients where the course of treatment is not obvious may be more
severely ill.
In this take-home exam you will be asked to perform several statistical analyses using
these data. The analyses you will be using are comprehensive, thus any statistical method
we have looked at in this class may be needed/used to answer the questions.
These data are contained in the file: Right Heart Catheterization.JMP. The
descriptions of all the variables in the data file are found in the tables on the next two
pages.
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VARIABLE DESCRIPTIONS FOR RHC DATASET
Variable name
Age
Sex
Race
Education
Income
Insurance
Disease Category
Variable Definition
Age (yrs.)
Sex (Female or Male)
Race (white, black, other)
Years of education (yrs.)
Income coded as follows:
1 – Under $11k, 2 - $11k - $25k, 3 - $25k - $50k, 4 - $50k+
Medical insurance type coded as:
Private & Medicare, Private, Medicare, Medicare &
Medicaid, Medicaid, No Insurance
Primary disease category coded as:
MOSF w/Sepsis, MOSF w/Malignancy, Lung Cancer,
COPD, Coma, Colon Cancer, Cirrhosis, CHF, ARF
Categories of admission diagnosis:
Respiratory
Cardio
Neuro
Gastro
Renal
Meta
Hema
Sepsis
Trauma
Ortho
DASI
DNR
Cancer
Surv2md1
Apache Score
Glasgow Coma
WtKilo
Temp (C)
MeanBP
Resp Rate
Heart Rate
PaFi
PaCO2
pH
WBC
Hemocrit
Sodium
Potassium
Creatinine
Bilirubin
Albumin
Respiratory Diagnosis (Yes or No)
Cardiovascular Diagnosis (Yes or No)
Neurological Diagnosis (Yes or No)
Gastrointestinal Diagnosis (Yes or No)
Renal Diagnosis (Yes or No)
Metabolic Diagnosis (Yes or No)
Hematologic Diagnosis (Yes or No)
Sepsis Diagnosis (Yes or No)
Trauma Diagnosis (Yes or No)
Orthopedic Diagnosis (Yes or No)
DASI ( Duke Activity Status Index)
DNR status on day1
Cancer (Yes, No, or Metastatic)
Support model estimate of the prob. of surviving 2 months
APACHE score – higher scores indicate severity of illness
and higher chance of death.
Glasgow Coma Score – 15-point scale, LOW values indicate
severity of brain trauma or lack of brain function.
Weight (kg)
Temperature in degrees Celsius
Mean blood pressure – not sure if this is diastolic or systolic
BP, looks to me that it might have been coded differently for
some patients.
Respiratory rate (breaths per minute)
Heart rate (bpm)
PaO2/FIO2 ratio
PaCO2 level
Blood pH
White blood cell count
Hematocrit - % volume of red blood cells in the blood
Sodium level
Potassium level
Creatinine level
Bilirubin level
Albumin level
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Categories of comorbidities illness:
CardioHx
CHFHx
DementHx
PsychHx
CPDHx
RenalHx
LiverHx
History of Cardio Problems: Y or N
Yes means they have had one of the following conditions:
Acute MI, Peripheral Vascular Disease, Severe
Cardiovascular Symptoms (NYHA-Class III), Very Severe
Cardiovascular Symptoms (NYHA-Class IV)
History of Congestive Heart Failure: Y or N
History of Dementia Problems: Y or N
Yes means they have had one of the following conditions:
Dementia, Stroke or Cerebral Infarct, Parkinson’s Disease
History of Psychological Problems: Y or N
Yes means they have had one of the following conditions:
Psychiatric History, Active Psychosis or Severe Depression
History of Chronic Pulmonary Disease: Y or N
Yes means they have had one of the following conditions:
Chronic Pulmonary Disease, Severe Pulmonary Disease,
Very Severe Pulmonary Disease
History of Renal Disease: Y or N
Yes means they have had one of the following conditions:
Chronic Renal Disease, Chronic Hemodialysis or Peritoneal
Dialysis
History of Liver Disease: Y or N
Transfer
Yes means they have had one of the following conditions:
Cirrhosis, Hepatic Failure
History of Gastrointestinal Bleeding: Y or N
Yes means they have had Upper GI Bleeding
History of Malignancies: Y or N
Yes means they have had one of the following conditions:
Solid Tumor, Metastatic Disease, Chronic
Leukemia/Myeloma, Acute Leukemia, Lymphoma
History of Immunosuppresion: Y or N
Yes means they have had one of the following conditions:
Immunosupperssion, Organ Transplant, HIV Positivity,
Diabetes Mellitus Without End Organ Damage, Diabetes
Mellitus With End Organ Damage, Connective Tissue
Disease
Transfer (> 24 Hours) from Another Hospital: Y or N
MIHx
History of Myocardial Infection (MI): Y or N
Swang
Definite Myocardial Infarction
Did patient have a Swan-Ganz Catheter: Y or N
Death
Death30
Patient ID
Right Heart Catheterization (RHC)
Death at any time up to 180 Days
Death at any time up to 30 Days
Patient identification number
GIbleedHx
MaligHx
ImmunHx
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For each question include all relevant JMP output. If the test yields a statistically
significant result be sure include relevant measures of the size of the effect, i.e. provide
appropriate confidence interval(s) to quantify. Also be sure to check and discuss any
assumptions that are required for the test you are using to be valid.
1. Compare the risk of death within 30 days (Death30) for those that had a right
heart catheter used during their treatment (Swang) vs. those that did not. Conduct
an appropriate test to make this comparison and provide a confidence interval for
the risk of 30-day mortality associated with having a RHC used. Discuss. (6 pts.)
2. Compare the risk of death within 180 days (Death) for those that had a right heart
catheter used during their treatment (Swang) vs. those that did not.
a) Conduct an appropriate test to make this comparison and provide a confidence
interval for the risk of 180-day mortality associated with having a RHC used.
(6 pts.)
b) For which mortality rate, 30-day or 180-day, is the risk associated with having
a RHC used during the course of treatment greater? Justify your answer. (2 pts.)
3. Is there evidence that the 30-day or 180-day death rate differ across the sex of the
patient? Justify your answer. (4 pts.)
4. a) Is there evidence that the 30-day death rate differs across DNR status? (4 pts.)
b) Is there evidence that the DNR status differs for those who had a Swan-Ganz
line used versus those that did not? (4 pts.)
c) What are the potential implications of these findings in terms of assessing the
risk associated with the Swan-Ganz line? (2 pts.)
5. Compare the mean APACHE scores for patients that had a right catheter used
during their treatment vs. those that did not.
a) Conduct an appropriate test to make this comparison and quantify the
difference in the population means if you conclude the means significant
differ. (6 pts.)
b) What is the potential implication of your results in part (a) in terms your
results from the comparison of the 30-day death rates in problem 1? (2 pts.)
6. Is there a relationship between type of insurance the patient has (Insurance) and
their race (Race)? If so, briefly summarize the nature of this relationship citing
appropriate percentages in the process. (6 pts.)
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7. a) Estimate the percentage of patients with a prior history of cardiology problems
(CardioHx) in this study using a 95% CI. Interpret this interval. (4 pts.)
b) Does this CI provide evidence that in the population of critically ill patients
being treated in an ICU over 10% of them have a prior history of cardiology
problems. Justify your answer. (2 pts.)
8. Is there a significant relationship between the age of the patient (Age) and their
APACHE score? Explain. (3 pts.)
9. Does the 30-day death rate (Death30) differ across race of the patient (Race)?
Conduct an appropriate test to answer this question and summarize your findings
and discuss any differences. (6 pts.)
10. Does the type of insurance (Insurance) relate to whether or not the patient had a
RHC used (Swang) during their treatment? Conduct an appropriate test to
answer this question and summarize your findings and discuss any differences.
(6 pts.)
11. On average how much older are patients that died within 30 days than those that
did not die. Provide a CI for the difference in the mean ages of these two
populations of patients. Interpret. (4 pts.)
12. While this may be of little medical interest…
a) Compare the mean years of education (Education) across the four income
levels (Income) using an appropriate statistical test. Summarize your result.
(5 pts.)
b) If significant differences in the mean years of education were found, conduct
an appropriate analysis to determine which means significantly differ across
the income levels. Interpret the CI corresponding to the largest mean
difference. (5 pts.)
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