Module 2.2 Unit 6 Assignment 7

Total grades =30 marks

Question 1[15]

In study, examination of eyes, where compared between a general practitioner (GP) vs.

an ophthalmologist, the study are depicted in the table below

Comparison of results between GP & ophthalmologist (N=400 eyes)

	No DR	DR	Totals
No DR	123	7	130
DR	19	251	270
Totals	142	258	400

a. Calculate % agreement (2)

b. Agreement by chance (3)

c. Kappa (5)

Show calculations and formulas

d. Explain your findings (5)

Question 2(15)points

A total of 80 subjects were tested for HIV using ELISA, suppose 12 of the 20 diagnosed

with HIV using Western blot (true status) tested positive and 3 of the non-diseased

subjects tested positivedetected by ELISA.

1. Construct a 2 x 2 table to depict this situation(1)

	HIV+	HIV-
ELISA+
ELISA-
Total

b. Calculate Sensitivity and specificity (4)

Interpret your findings

c. What is the: (6)

Prevalence of HIV in this population

Predictive value positive = PVP

Predictive value negative = PVN

Interpret your findings

d. What is the false positive rate? Comment on the type of error (2)

Interpret your findings

e. What is the false negative rate? Comment of the error (2)

Interpret your findings