Introduction to Clinical Epidemiology: Analysis of Diagnostic Test and Research Article

Running head: INTRODUCTION TO CLINICAL EPIDEMIOLOGY
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Introduction to clinical epidemiology
Name of Student
Institutional Affiliation
Name of Professor
Date

INTRODUCTION TO CLINICAL EPIDEMIOLOGY
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Introduction to clinical epidemiology
Q6: Answer questions 6a-c based on the following information: A total of 1500 children
have a rapid strep test (RST) done by a standardized culture technique. Of the 1500
children, 1338 have a negative RST and 162 have a positive RST. In addition, a backup
throat culture (gold standard) was done on all children. Of those children with a negative
RST, 1302 have a negative throat culture. In the group with a positive RST, 159 have a
positive throat culture.
Q6: Construct a 2x2 table using the information provided above, and answer the following
questions (a-c):
A 2x2 table
Target disorder (strep tonsillitis)
Present Absent Totals
Diagnostic Test
Result
Positive RST 159 3 162
Negative
RST
36 1302 1338
195 1305 1500
a) Calculate the sensitivity of the RST [2 marks]
Sensitivity= TP/ (TP+FN)
Sensitivity = 159/ (159+36)

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Sensitivity = 159/195
= 0.815
=81.5%
b) Calculate the specificity of the RST [2 marks]
Specificity = TN/ (FP+TN)
Specificity = 1302/ (3+1302)
Specificity = 1302/ 1305
= 0.997
= 99.7%
c) Calculate the positive predictive value of the RST [2 marks]
The positive predictive value is given by the probability of the disease among
patients with a positive test.
PPV= TP/ (TP+FP)
=159/ (159+3)
=159/162
=0.9815
= 98.15%

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d) In a test with high sensitivity, a negative result rules in the diagnosis [True/False] [1
marks]
True
e) In a test with high specificity, a positive result rules out the diagnosis [True/False]
[1 marks]
True
f) The positive predictive value is dependent on all of the following: prevalence,
incidence, sensitivity and specificity [True/False] [1 mark]
True
g) Using the image below, which value in the test result units is the point of maximum
specificity. [1 mark]
a) 20 b) 15 c) 5 d) 30 e) 25 The point of maximum specificity = 30