This is a book about diagnostic testing. It is aimed primarily at clinicians, particularly those who are academically minded, but it should be helpful and accessible to anyone involved with selection, development, or marketing of diagnostic, screening, or prognostic tests. Although we admit to a love of mathematics, we have restrained ourselves and kept the math to a minimum – a little simple algebra and only three Greek letters, κ (kappa), α (alpha), and β (beta). Nonetheless, quantitative discussions in this book go deeper and are more rigorous than those typically found in introductory clinical epidemiology or evidence-based medicine texts.

Our perspective is that of skeptical consumers of tests. We want to make proper diagnoses and not miss treatable diseases. Yet, we are aware that vast resources are spent on tests that too frequently provide wrong answers or right answers of little value, and that new tests are being developed, marketed, and sold all the time, sometimes with little or no demonstrable or projected benefit to patients. This book is intended to provide readers with the tools they need to evaluate these tests, to decide if and when they are worth doing, and to interpret the results.

The pedagogical approach comes from years of teaching this material to physicians, mostly Fellows and junior faculty in a clinical research training program. We have found that many doctors, including the two of us, can be impatient when it comes to classroom learning.