Glossary of terms


This is one of a set of measures used to assess the accuracy of a diagnostic test (see sensitivity, negative predictive value and positive predictive value). Specificity is the proportion of people without a disease who are correctly identified as not having that disease by the diagnostic test. For example, if a test has a specificity of 95%, this means that it correctly identified 95% of the people who did not have the disease, but that 5% of people without the disease were incorrectly diagnosed as having the disease (these people were ‘false positives’ on the test).

Statistical significance

If the results of a test have statistical significance, it means that they are not likely to have occurred by chance alone. In such cases, we can be more confident that we are observing a ‘true’ result.

Systematic review

This is a synthesis of the medical research on a particular subject. It uses thorough methods to search for and include all or as much as possible of the research on the topic. Only relevant studies, usually of a certain minimum quality, are included.

Time trend studies

Time trend studies are epidemiological studies that describe characteristics of a population over time. They look at trends at the population level (rather than in individuals) through taking repeated cross sectional samples.

Tissue engineering

Tissue engineering is an interdisciplinary field that applies the principles of engineering and biological sciences to developing functional substitutes for damaged tissue.

Twin studies

Twin studies rely on comparing the phenotypes (observable physical traits) of monozygotic (genetically identical) twins and dizygotic (non-identical) twin pairs. The difference in correlation between phenotypes in the identical twins and the correlation in phenotypes in the non-identical twins estimate the genetic contribution to variations in phenotype (the within-twin correlation).

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