Sexual Health | Pathology | Interpreting Laboratory Tests

Interpreting Laboratory Tests
Session Overview
Description
This session explains what is meant by sensitivity and specificity of tests and how these translate into measures of positive predictive value and negative predictive value. The difference between diagnostic testing and screening for disease is discussed with appropriate examples.

Learning Objectives
By the end of this session you will be able to:

• Define the terms 'sensitivity' and 'specificity' in relation to laboratory tests
• Describe what is meant by the terms 'positive predictive value' and 'negative predictive value'
• Calculate positive and negative predictive values
• Interpret positive and negative predictive values in clinical practice
• Describe the difference between diagnostic testing and screening

No laboratory test is perfect: a test may give a correct result that is positive or negative, but it may also give a result that is wrongly positive or negative. Incorrect test results can cause the physician to make incorrect decisions about the care of patients. This can be very important in genitourinary medicine where diagnoses such as HIV infection have immediate, serious and life-long implications for patients, and where many other diagnoses have social and public health implications.

The aims of this session are to provide an understanding of the limitations of laboratory tests, how these limitations are measured in test accuracy studies, and how test accuracy must be considered when requesting and interpreting the results of laboratory tests.