Question

d) Assume that the same screening test is applied to a high-risk population of intravenous drug users, who are at high risk of AIDS. If you had access to 1,000 IV drug users and could obtain permission to test them for HIV antibody status, and if past studies have estimated that 20% of IV drug users are truly HIV positive, what value will you obtain for the positive predictive value (PPV) in this population? Hint: you have to calculate again the numbers of people for each cell of the 2 x 2 table below (round the numbers

Calculations:

a + b + c + d = total high-risk population screened = 1,000

(a + c) = Prevalence * total population =

(b + d) = 1,000 –

a =

c =

d =

b =

Results Table:

HIV Antibody Test	Actual HIV Antibody Status		Total
	Present	Absent
Positive			200
Negative			800
Total			1,000

Answer 1

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The question is complete, as the data is not visible.

But here' how to solve the problem.

PPV = A/(A+B). ...........................................1

We have been given A+B as 200

C+D as 800

A+B+C+D = 1000

Sub the value of A in (1) to get the PPV. So, basically PPV = A/200