Appendix G: Glossary

Abstraction

The method by which reviewers or researchers read scientific articles and then collect and record data from them.

AHRQ

Agency for Healthcare Research and Quality.

Allocation concealment

The processes used to prevent knowledge of group assignment in a randomized controlled trial before the actual intervention/treatment/exposure is administered. This process should be seen as distinct from blinding or masking of treatment group after the allocation process. The allocation process should be impervious to any influence by the individual making the allocation by having the randomization process administered by someone who is not responsible for recruiting participants.

Bias

Any systematic error in the design, conduct, or analysis of a study that results in a mistaken estimate of effect.

Case-control study

A type of observational study. Patients who have developed a disease or condition are identified and their past exposure to suspected etiological factors is compared with that of controls or referents who do not have the disease or condition.

The Cochrane Library©

An electronic publication of The Cochrane Collaboration, an international group dedicated to preparing, maintaining, and promoting the accessibility of systematic reviews of the effects of health care interventions.

Cohort study

A type of observational study. Factors related to the development of disease are measured initially in a group of persons, known as a cohort. The group is followed over a period of time and the relationship of a factor to the disease is examined. The population may be divided into subgroups according to the level or presence of the factor initially and comparing the subsequent incidence of disease in each subgroup.

Cohort

A subset of a population with a common feature, such as age, sex, or occupation.

Consistency

For any given topic, the extent to which similar findings are reported using similar or different study designs.

CONSORT

Consolidated Standards of Reporting Trials. A checklist of guidelines and items to be addressed when preparing published reports of RCTs.

Controls

A group of study subjects with whom a comparison is made in an epidemiologic study. For example, in a case-control study, cases are persons who have the disease and controls are persons who do not have the disease.

Diagnostic study

A study that examines the sensitivity and specificity of a particular test to evaluate to presence and/or absence of disease.

Domain

A quality construct relating to some aspect of study design or conduct considered important in determining the extent to which a study is valid.

Empirical

A concept designating that work is based directly on observational or experimental study, rather than theory or reasoning alone.

EPC

AHRQ Evidence-based Practice Center.

External validity

The extent to which a study can produce unbiased inferences regarding a target population (beyond the subjects of the study).

Gray literature

Materials that are found in recorded, written, or electronic form that are not traditionally well indexed or readily available. Examples are conference papers, white papers, technical reports, electronic theses and dissertations, online documents, and oral presentations/abstracts.

Guidance document

Publication that defines or describes study quality, but does not provide an instrument that could be used for evaluative applications.

Guidelines

Recommendations or principles presenting current or future guidance of policy, practice, or procedure. Guidelines are developed by government agencies at any level -- institutions, professional societies, governing boards -- or by the convening of expert panels. The formal definition of "clinical practice guidelines" comes from a 1990 report from the Institute of Medicine: "PRACTICE GUIDELINES are systematically developed statements to assist practitioner and patient decisions about appropriate health care for specific clinical circumstances."

Internal validity

The extent to which a study describes the "truth." A study conducted in a rigorous manner such that the observed differences between the experimental or observational groups and the outcomes under study may be attributed only to the hypothesized effect under investigation.

Inter-rater reliability

A measure of the extent to which multiple raters or judges agree when providing a rating, scoring, or assessment.

Magnitude of effect

The size or strength of the estimated association or effect observed in a given study. Magnitude of effect is often expressed as a odds ratio (OR) or relative risk (RR).

MEDLINE©

A comprehensive database, updated weekly, of bibliographic materials containing nearly 11 million records from more than 7,300 publications from 1965. It is compiled by the U.S. National Library of Medicine (NLM) and published on the Web by Community of Science.

Meta-analysis

The process of using statistical methods to combine quantitatively the results of similar studies in a systematic review.

Methodology

The scientific study of methods, or the practices and procedures used to plan, conduct, and analyze the results of a scientific study.

MOOSE

Meta-analysis Of Observational Studies in Epidemiology. A consensus workshop held in Atlanta, Georgia, in April 1997, convened by the Centers for Disease Control and Prevention, to examine the reporting of meta-analyses of observational studies and to make recommendations.

Peer-reviewed literature

Publications including research proposals, manuscripts submitted for publication, and abstracts submitted for presentation at scientific meetings that are judged for scientific and technical merit by other scientists in the same field.

Prospective cumulative meta-analysis

A meta-analysis that is conducted by adding each new study's results on a particular topic as it is available.

Quality checklists

Instruments that contain a number of quality items, none of which is scored numerically.

Quality component

Individual aspect of study methodology -- for example, randomization, blinding, follow-up -- that has a potential relation to bias in estimation of effect.

Quality scales

Instruments that contain several quality items that are scored numerically to provide a quantitative estimate of overall study quality.

QUORUM

The Quality of Reporting of Meta-Analyses. A QUORUM statement, checklist, and flow diagram stemming from a conference to address standards for improving the quality of reporting of meta-analyses of randomized controlled trials.

Randomization

The process of allocating a particular experimental intervention or exposure to a group at random, in order to control for all other factors that may affect disease risk.

Randomized clinical trial (RCT)

A clinical trial that involves at least one treatment and one control group, concurrent enrollment, and follow-up of the groups, and in which the treatments to be allocated are selected by a random process, such as the use of a random numbers table.

Retrospective cohort study

A type of observational study. This study design begins with a group of affected individuals and tests the hypothesis that some prior characteristic or exposure is more common in persons with the disease than in unaffected persons.

Selection bias

Error attributable to systematic differences in characteristics between those who are selected for study and those who are not.

Sensitivity

The proportion of truly diseased persons in the screened population who are identified as diseased by the screening test -- that is, the true-positive rate.

Sensitivity analysis

Determining the robustness of analysis by examining the extent to which changes in methods, values of variables, or assumptions change results. The aim is to identify variables whose values are most likely to alter results or to find a solution that is relatively stable for the commonly occurring values of these variables.

Specificity

The proportion of truly nondiseased persons who are identified as such by the screening test -- that is, the true-negative rate.

STARD

STAndards for Reporting Diagnostic Accuracy. Developed by an international group addressing the need for quality measures for studies of diagnostic services.

Statistical power

The statistical ability of a study to correctly identify a true difference between therapies. Power chiefly depends upon the number of subjects in a study and the response rate of the study groups.

Systematic review

An organized method of locating, assembling, and evaluating a body of literature on a particular topic using a set of specific predefined criteria. A systematic review may be purely narrative or may also include a quantitative pooling of data, referred to as a meta-analysis.

TEAG

Technical Expert Advisory Group

Temporality

The relationship of time and events such as exposure to a risk factor and the development of disease. To implicate the exposure as causative of the disease, the exposure should have occurred before the disease.