I.A. 2a
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School
Queens University *
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Course
270
Subject
Mathematics
Date
Apr 3, 2024
Type
docx
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2
Uploaded by vvictoria31
Question:
Which cut-off value would you choose as optimal for each of CK-MB and Troponin I and briefly
explain why.
The optimal cut-off values for CK-MB and Troponin I are 16 and 7.5, respectively. These values
have specificity closest to value under the ROC curve.
Question:
Which biomarker appears to perform better? Is there another way you may be able to look at the data to answer this question?
The NSTEMI biomarker appears to perform better. By looking at the number of true positives of each biomarker, it is seen that NSTEMI has more true positives than that of the NO MI biomarker. Its sensitivity and specificity are more accurate.
Part B:
An ROC curve is a helpful way to compare the overall performance of a biomarker. Recall that an ROC curve is made by plotting the sensitivity and 1 – specificity at various cut-off points.
Question:
Using this information, generate an ROC curve for each of the biomarkers and provide the curves as part of your submission for this assignment.
Question:
Using the values determined above, generate an ROC curve for each laboratory test.
Question:
Based on the ROC curves, which of the tests (troponin I or CK-MB) performs better at differentiating patients with NSTEMI and those without MI?
According to the AUC values, the Troponin I biomarker is better at differentiating patients.
Question:
Calculate the positive likelihood ratio for troponin I at a cut-off of 8.5 ng/mL?
LR = Sensitivity / (1-Specificity)
= 0.3125
Question: Using Bayes’ Theorem to determine post-test probability of NSTEMI with the following scenarios and using the likelihood ratio calculated in question #4:
a.
Pre-test probability: 30%
b.
Pre-test probability: 80%
Question:
These pre-test probabilities were given to you, but given what you know about acute coronary syndrome, what would be an approach you may recommend for a clinician in the ED
CK-MB
22 nstemi
3 nomi
Troponin
29 tp nstemi
3 no mi
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