Glossary

Sensitivity

Proportion of those people who have the disease who are correctly detected by the test.

Specificity

Proportion of those people who do not have the disease who are correctly left undetected by the test.

Negative Predictive value

Proportion of those testing negative who are truly disease free.

Positive Predicative Value

Proportion of those testing positive who truly have the disease.

Diagnostic test

Test offered to people who have a specific indication of possible illness (a history, symptom, sign or screening test result) to determine whether or not they have the disease in question.

Screening test

Test offered to asymptomatic people who may or may not have early disease or disease precursor and are sued to guide whether or not a diagnostic test should be offered.

Parallel testing

screening tests performed at the same time and the results are subsequently combined.

Serial testing

Second screening test is performed only if the result of the first screening test is positive.

True positive test result

A person with the condition tested for, and a positive test result.

False positive test result

A person without the condition tested for, and a positive test result.

True negative test result

A person without the condition tested for, and a negative test result.

False negative test result

A person with the condition tested for, and a negative test result.

Receiver operating characteristic (ROC)

Is a plot of sensitivity versus 1- specificity.

Inter-rater reliability

is the degree of agreement among raters of the result of a diagnostic test. If there is significant disagreement of a test outcome between raters, either the scale is defective or better training needs to be provided for those who use the test.

Test-retest reliability

Is used to determine a test's reliability. A diagnostic test on the same person in short succession should provide the same test result. However, the same test result on the same person over a long period may result from a test's inability to detect subtle changes.

Prevalence of a disease

Proportion of a population with a disease.