JAMAevidence Glossary

Terms are derived from Users' Guides to the Medical Literature: A Manual for Evidence-Based Practice, 2nd Edition and The Rational Clinical Examination: Evidence-Based Clinical Diagnosis. Updated March 2010.
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Malrotation
Improper rotation of a body part (eg, the intestines).

Manning criteria
Combinations of findings used to diagnose irritable bowel syndrome. See Table 55-2 in The Rational Clinical Examination.

MANTRELS
The MANTRELS mnemonic is a helpful tool used to diagnose appendicitis. This mnemonic is a part of the Alvarado clinical decision rule and examines 8 findings from the medical history or the examination. The various components are Migration, Anorexia-acetone, Nausea-vomiting, Tenderness in RLQ, Rebound pain, Elevation of temperature, Leukocytosis, and Shift to the left of normal WBC count. See Table 5-5 in The Rational Clinical Examination.

Marginal utility
The change in a person’s utility (preference or relative value) for an outcome as the outcome increases in magnitude.

Markov model
Markov models are tools used in decision analyses. Named after a 19th-century Russian mathematician, Markov models are the basis of software programs that model what might happen to a cohort of patients during a series of cycles (eg, periods of 1 year). The model allows for the possibility that patients might move from one health state to another. For instance, one patient may have a mild stroke in one 3-month cycle, continue with minimal functional limitation for a number of cycles, have a gastrointestinal bleeding episode in a subsequent cycle, and finally experience a major stroke. Ideally, data from randomized trials will determine the probability of moving from one state to another during any cycle under competing management options.

Matching
A deliberate process to make the study group and comparison group comparable with respect to factors (or confounders) that are extraneous to the purpose of the investigation but that might interfere with the interpretation of the study’s findings. For example, in case control studies, individual cases may be matched with controls on the basis of comparable age, gender, and/or other clinical features.

Median survival
Length of time that one-half of the study population survives.

Medical subject headings
The U.S. National Library of Medicine's controlled vocabulary used for indexing articles for MEDLINE/PubMed. MeSH terminology provides a consistent way to retrieve information that may use different terminologies for the same concepts.

Member checking
In qualitative research, this involves sharing draft study findings with the participants to inquire whether their viewpoints were faithfully interpreted and to ascertain whether the account makes sense to participants with different perspectives.

Memory disorders
Associated with delirium and memory impairment.

Memory Impairment Screen
A quick test of recall ability where a patient is asked to recall items representing 4 different categories. Its advantages include the simplicity of the approach and uncomplicated scoring.

Messenger RNA
A ribonucleic acid-containing single-strand copy of a gene that migrates out of the cell nucleus to the ribosome, where it is translated into a protein.

Meta-analysis
A statistical technique for quantitatively combining the results of multiple studies that measure the same outcome into a single pooled or summary estimate.

Meta-regression analysis
When summarizing patient or design characteristics at the individual trial level, meta-analysts risk failing to detect genuine relationships between these characteristics and the size of treatment effect. Furthermore, the risk of obtaining a spurious explanation for variable treatment effects is high when the number of trials is small and many patient and design characteristics differ. Meta-regression techniques can be used to explore whether patient characteristics (eg, younger or older patients) or design characteristics (eg, studies of low or high quality) are related to the size of the treatment effect.

Meta-synthesis
A procedure for combining qualitative research on a specific topic in which researchers compare and analyze the texts of individual studies and develop new interpretations.

Migraine
A neurological condition characterized by altered bodily perceptions, recurrent usually unilateral severe headaches, and nausea.

Mini-Mental Status Examination (MMSE)
A screening instrument for assessing the severity of dementia and communicating the severity to other clinicians. MMSE scores have been shown to be influenced by educational levels. This is the most studied of the brief cognitive tests.

Minimal important difference
The smallest difference in a patient-important outcome that patients perceive as beneficial and that would mandate, in the absence of troublesome adverse effects and excessive cost, a change in the patient’s health care management.

Mixed-methods study
A study that combines data collection approaches, sometimes both qualitative and quantitative, into the study methodology and is commonly used in the study of service delivery and organization. Some mixed-methods studies combine study designs (eg, investigators may embed qualitative or quantitative process evaluations alongside quantitative evaluative designs to increase understanding of factors influencing a phenomenon). Some mixed-methods studies include a single overarching research design but use mixed-methods for data collection (eg, surveys, interviews, observation, and analysis of documentary material).

Model
Often used to describe statistical regression analyses involving more than one independent variable and one dependent variable. This is a multivariable or multiple regression (or multivariate) analysis.

Mortality
Measure of rate of death.

Multiple regression
A type of regression that provides a mathematical model that explains or predicts the dependent or target variable by simultaneously considering all of the independent or predictor variables. See also Multivariate regression analysis.

Multivariate regression analysis
A type of regression that provides a mathematical model that attempts to explain or predict the dependent variable (or outcome variable or target variable) by simultaneously considering 2 or more independent variables (or predictor variables). See also Multiple regression.

Murphy sign
Pain and arrested inspiration occurring when the patient inspires deeply while the examiner's fingers are hooked underneath the right costal margin.

Mutation
A rare variant in a gene, occurring in <1% of a population. See also Polymorphism.

Myalgia
Muscle discomfort.

Myerson sign
Persistent blinking during the Glabella tap test used to diagnose Parkinson disease.