Statistics In Diagnostics for USMLE

In Episode 6 of Med School Question of the Week for USMLE, Luke Maxfield, MedSchoolCoach expert tutor, answers this medical school question:

A physician is in the process of developing a serologic test to determine the presence of sarcoidosis. While evaluating this study serum levels of Anti-X- protein will be measured. The presence of Anti-x-protein will be compared to tissue biopsies demonstrating non-caseating granulomas as the control. 200 patients were recruited and 120 had positive biopsy results. Anti-X protein was found in 80 patients with sarcoidosis and was positive in 15 patients without the disease. What is the specificity of the test?

• 0.67
• 0.84
• 0.62
• 0.81
• 2.21