What is the PV+ of the CDC algorithm?

Infectious Disease, Cardiovascular Disease

A validation study is to be performed in a local hospital to check the accuracy of assessment of hospital-acquired infection (INF) following coronary bypass surgery (coronaryartery bypass graft, or CABG). In a given year the hospital performs 1100 CABG procedures. A Centers for Disease Control and Prevention (CDC) algorithm is currently used to categorize subjects as having INF. To validate this algorithm, all CDC+ subjects (N = 100) and a random sample of CDC− subjects (N = 1000) will be ascertained by an infectious-disease (ID) fellow and a detailed investigation will be performed, including a chart review and documentation of antibiotic use. Assume the ID-fellow’s determination is correct.
Suppose 100 CDC+ subjects are ascertained, of whom the ID fellow confirms 80. Because there are a large number of CDC− subjects (1000), only a sample of 100 is studied, of whom the ID fellow confirms 90.