Stats #21: What Do All These Numbers Mean? Sensitivity and Specificity

Content:  This two hour training class will teach you some of the numbers used to describe medical diagnostic tests. This class is useful for anyone who reads journal articles that evaluate these tests. Please bring a pocket calculator.

Objectives:  In this class you will learn how to:

• compute sensitivity and specificity;
• identify the problems with diagnosing a rare disease;
• understand which tests are useful for ruling in or ruling out a disease.

Teaching strategies:  Didactic lectures and small group exercises.

IRB Education Credits:  This class does not qualify for IRB Education Credits (IRBECs).

Outline:

• Overview of the STATS web pages
• Consulting services that I provide
• Diagnostic test
• Sensitivity
• Specificity
• Positive Predictive Value
• Negative Predictive Value
• ROC curve
• Please fill out an evaluation form

Notes:  I will also use the following papers in class as examples:

• Accuracy of a single question in screening for depression in a cohort of patients after stroke: comparative study. Watkins C, Daniels L, Jack C, Dickinson H, van Den Broek M. Bmj 2001: 323(7322); 1159. [PDF]
• The SCOFF questionnaire and clinical interview for eating disorders in general practice: comparative study. Luck AJ, Morgan JF, Reid F, O'Brien A, Brunton J, Price C, Perry L, Lacey JH. British Medical Journal 2002: 325(7367); 755-6. [PDF]
• Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma. Hoffman JR, Mower W, Wolfson A, Todd K, Zucker M. The New England Journal of Medicine 2000: 343(2); 94-99. [PDF]
• Simple tests for septic bursitis: comparative study. Stell IM, Gransden WR. Bmj 1998: 316(7148); 1877. [PDF]
• A survey of validity and utility of electronic patient records in a general practice. Hassey A, Gerrett D, Wilson A. British Medical Journal 2001: 322(7299); 1401-5. [PDF]

For the extended version of this class, I will also use the following page of recent weblog entries about diagnostic testing:

• Stats #21/#24: Additional readings