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JAMAevidence Glossary

Terms are derived from Users' Guides to the Medical Literature: A Manual for Evidence-Based Practice, 2nd Edition, The Rational Clinical Examination: Evidence-Based Clinical Diagnosis and Care at the Close of Life: Evidence and Experience. Updated October 2014.
Download a PDF of the glossary (295 KB). (Adobe Reader is required to open or print PDF files.)

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Calman gap
The gap between the patient’s hopes and expectations and what the patient actually experiences.

Cancer-related fatigue
A distressing persistent, subjective sense of tiredness or exhaustion related to cancer or cancer treatment that is not proportional to recent activity and that interferes with usual functioning.

Candidate gene study
A study that evaluates association of specific genetic variants with outcomes or traits of interest, selecting the variants to be tested according to explicit considerations (known or postulated biology or function, previous studies, etc).

The per-person rate an insurance company pays to a clinician (or group of clinicians) for care of patients enrolled in a managed care health insurance plan.

Cardiac cachexia
Nonintentional, nonedema weight loss of 7.5% of previous normal weight over a period of 6 months in patients with congestive heart failure or other heart disease.

Cardiac tamponade
Cardiac tamponade occurs when fluid trapped in the pericardial space compresses the heart and compromises cardiac output. The consequences of cardiac tamponade range from barely detectable effects to overt hemodynamic collapse.

Cardiopulmonary resuscitation (CPR)
An emergency procedure that attempts to to restore normal breathing and/or circulation after respiratory and/or cardiac arrest. Includes clearing the air passages to the lungs, artificial circulation through rhythmic pressing on the patient’s chest, and artificial respiration.

Care tenor
The tone or quality of care.

A person who provides direct care to a patient (either at home or in health care settings), whether paid or unpaid.

Case reports
Descriptions of individual patients.

Case series
A report of a study of a collection of patients treated in a similar manner, without a control group. For example, a clinician might describe the characteristics of an outcome for 25 consecutive patients with diabetes who received education for prevention of foot ulcers.

Case study
In qualitative research, an exploration of a case defined by some boundaries or contemporary phenomena usually within a real-life context.

Case-control study
A study designed to determine the association between an exposure and outcome in which patients are sampled by outcome. Those with the outcome (cases) are compared to those without the outcome (controls) with respect to exposure to the suspected harmful agent.

Castell sign
A sign that indicates splenomegaly. The patient is placed in the supine position. Percussion is carried out in the lowest intercostal space in the left anterior axillary line in both expiration and full inspiration. In a normal expiration result, the percussion note remains resonant throughout this maneuver. Splenomegaly is diagnosed when the percussion note is dull or becomes dull on full inspiration.

Categorical variable
A categorical variable may be nominal or ordinal. Categorical variables can be defined according to attributes without any associated order (eg, medical admission, elective surgery, or emergency surgery); these are called nominal variables. A categorical variable can also be defined according to attributes that are ordered (eg, height such as high, medium, or low); these are called ordinal variables.

CDSS intervention
A clinical decision support system (CDSS) intervention is used with individual patients to guide diagnosis and therapy, plus provide feedback on performance and tips on patient management.

Central dopamine type 2 (D2) receptors
Dopamine receptors that control neural signaling modulating many important behaviors, such as spatial working memory. Opioid-induced nausea and vomiting are caused by their effects in the chemoreceptor trigger zone that are largely mediated through central D2 receptors, whereas opioid effects on the stomach producing gastroparesis are mediated through peripheral D2 receptors.

Cerebral hemorrhage
Bleeding into the brain tissue from a ruptured blood vessel. It can cause abrupt dysfunction of neurologic tissue, leading to neurologic deficits such as hemiparesis, hemisensory loss, aphasia, ophthalmoplegia, and visual field cuts.

Chadwick sign
When the mucous membranes of the vulva, vagina, and cervix become congested and take on a bluish-violet hue.

Chance-corrected agreement
The proportion of possible agreement achieved beyond what one would expect by chance alone, often measured by the kappa statistic.

Chance-independent agreement
The proportion of possible agreement achieved that is independent of chance and unaffected by the distribution of ratings, as measured by the φ statistic.

Channeling bias
Tendency of clinicians to prescribe treatment based on a patient’s prognosis. As a result of the behavior, in observational studies, treated patients are more or less likely to be high-risk patients than untreated patients, leading to biased estimate of treatment effect. See also Bias.

Checklist effect
1. The effect on clinicians’ behavior of having them record information, or their orders, using a structured data collection form. 2. The improvement seen in medical decision making because of more complete and structured data collection (eg, clinicians fill out a detailed form, so their decisions improve).

Chemoreceptor trigger zone (CTZ)
Functionally outside the blood-brain barrier, the chemoreceptor trigger zone is exposed to toxins in the bloodstream and cerebrospinal fluid that can stimulate vomiting.

Cheyne-Stokes respirations
A rhythmic waxing and waning of both respiratory pattern rate and tidal volumes that includes regular periods of apnea. In end-of-life situations, it occurs in patients with end-stage left ventricular failure or neurologic disease.

Child-Turcotte-Pugh Score
Score used to assess the prognosis of chronic liver disease. The score includes 5 clinical measures of liver disease, including ascites, encephalopathy, serum bilirubin level, serum albumin level, and prothrombin time. Each measure is scored from 1 to 3, with 3 indicating most severe derangement. Chronic liver disease is classified into class A (score 5-6), B (7-9), or C (10-15), and prognosis is directly correlated to class. For more information, see the following Web site for the scoring:

Chi-square test
A nonparametric test of statistical significance used to compare the distribution of categorical outcomes in two or more groups, the null hypothesis of which is that the underlying distributions are identical.

Self-replicating structures in the nucleus of a cell that carry the genetic information.

Chronic fatigue
Fatigue present in an individual at least 50% of the time that persists for at least 6 months.

Chronic fatigue syndrome
An illness predominantly affecting young adults and characterized by disabling fatigue of at least 6 months’ duration, accompanied by several other symptoms (such as sore throat, adenopathy, muscle pain, multijoint pain, and headache) that cannot be attributed to any alternative condition.

Chuang Prognostic Score
Score, based on presence or absence (or degree of) lung metastasis, liver metastasis, tiredness, ascites, edema, cognitive impairment, and recent weight loss, as well as Eastern Cooperative Group Oncology status, that correlates with 2-week survival in patients with cancer. For more information, see the following article for the scoring: Chuang RB, Hu WY, Chiu TY, Chen CY. Prediction of survival in terminal cancer patients in Taiwan: constructing a prognostic scale. J Pain Symptom Manage. 2004;28(2):115-122. [PMID: 15276192]

The cutting off of the foreskin of males as a sanitary measure in modern surgery or as a religious rite.

Widespread disruption of normal liver structure by fibrosis and the formation of regenerative nodules that is caused by various chronic progressive conditions affecting the liver (such as long-term alcohol abuse or hepatitis).

Clinical competence
A clinician's knowledge of a procedure, disease, or condition.

Clinical decision support system
A strategy for changing clinician behavior. An information system used to integrate clinical and patient information and provide support for decision-making in patient care. See also Computer decision support system.

Clinical Dementia Rating Scale
A scale used to quantify the severity of symptoms of dementia. A patient’s cognitive and functional performance is assessed in 6 areas including memory, orientation, judgment and problem solving, community affairs, home and hobbies, and personal care. Scores in each of these areas are combined to obtain a composite score ranging from 0 (no dementia) to 3 (severe dementia). For more information, see the following article for the scale: Hughes CP, Berg L, Danziger WL, Coben LA, Martin RL. A new clinical scale for the staging of dementia. Br J Psychiatr. 1982;140:566-572. [PMID: 7104545]

Clinical gestalt
The physician's overall intuitive sense of the likelihood of disease established after the clinical evaluation of the patient. The clinical evaluation may include risk factors, history, symptoms, signs, and basic laboratory or radiological studies.

Clinical practice guidelines
A strategy for changing clinician behavior. Systematically developed statements or recommendations to assist practitioner and patient decisions about appropriate health care for specific clinical circumstances. They present indications for performing a test, procedure, or intervention, or the proper management for specific clinical problems. Guidelines may be developed by government agencies, institutions, organizations such as professional societies or governing boards, or by convening expert panels.

Clinical prediction rules
A guide for practice that is generated by initially examining, and ultimately combining, a number of variables to predict the likelihood of a current diagnosis or a future event. Sometimes, if the likelihood is sufficiently high or low, the rule generates a suggested course of action.

Clock-Drawing Test
A cognitive screening test in which the patient is asked to draw a clock, including numbers and hands set to a specific time. See also cognition disorders.

Closed fist sign
Paresthesias in the distribution of the median nerve when the patient actively flexes the fingers into a closed fist for 60 seconds.

Cluster analysis
A statistical procedure in which the unit of analysis matches the unit of randomization, which is something other than the patient or participant (eg, school, clinic).

Cluster assignment
The assignment of groups (eg, schools, clinics) rather than individuals to intervention and control groups. This approach is often used when assignment by individuals is likely to result in contamination (eg, if adolescents within a school are assigned to receive or not receive a new sex education program, it is likely that they will share the information they learn with one another; instead, if the unit of assignment is schools, entire schools are assigned to receive or not receive the new sex education program). Cluster assignment is typically randomized, but it is possible (though not advisable) to assign clusters to treatment or control by other methods.

Cluster-type headache
Headache that presents as excruciating pain around the eye and temple and comes and goes in a “cluster” like pattern.

Cochrane Q
A common test for heterogeneity that assumes the null hypothesis that all the apparent variability between individual study results is due to chance. Cochrane Q generates a probability, presented as a P value, based on a 2 distribution, that between-study differences in results equal to or greater than those observed are likely to occur simply by chance.

Code of Medical Ethics
The American Medical Association’s Code of Medical Ethics is an ethics guide for practicing physicians that is reviewed and updated over time.

Cognition disorders
Disorders such as dementia and delirium that involve mental activities associated with thinking, learning, and memory.

Cognitive Test for Delirium
Test designed to assess patients with possible delirium, in particular those who are intubated or unable to speak or write. It assesses 5 neuropsychological domains (orientation, attention, memory, comprehension, and vigilance), emphasizing nonverbal (visual and auditory) modalities. Total scores range from 0 to 30, with higher scores indicating better cognitive function. This test helps to differentiates delirium from other neuropsychiatric conditions, including dementia, schizophrenia, and depression. For more information, see the following article for the test: Hart RP, Levenson JL, Sessler CN, et al. Validation of a cognitive test for delirium in medical ICU patients. Psychosomatics. 1996;37:533-546). [PMID: 8942204]

The agreement in treatment effect estimates between direct and indirect evidence.

A group of persons with a common characteristic or set of characteristics. Typically, the group is followed for a specified period of time to determine the incidence of a disorder or complications of an established disorder (prognosis). See also Cohort study.

Cohort study
Study of a group of individuals, some of whom are exposed to a variable of interest (eg, a drug treatment or environmental exposure), in which participants are followed up over time to determine who develops the outcome of interest and whether the outcome is associated with the exposure.

Intervention other than intervention under study that affect the outcome of interest and that may be differentially applied to intervention and control groups and, thus, potentially bias the results of a study.

Comfort care suite
Hospital room with a more homelike environment and hospice-type protocol orders. Care is provided for dying patients who cannot leave the hospital for hospice care elsewhere, and there are often facilities for families to stay overnight and keep a death vigil.

Disease(s) or conditions that coexist(s) in study participants in addition to the index condition that is the subject of the study.

Compassion fatigue
Fatigue that evolves specifically from the relationship between the clinician and the patient. Compassion fatigue has been described as the “cost of caring” for others in emotional pain that has led helping professionals to abandon their work with traumatized persons. (See also Chapter 42, Self-care of Physicians Caring for Patients at the End of Life.)

Compassion satisfaction
Pleasure derived from the clinician’s work of helping patients and their caregivers. (See also Chapter 42, Self-care of Physicians Caring for Patients at the End of Life.)

Complete follow-up
The investigators are aware of the outcome in every patient who participated in a study.

Composite endpoint
When investigators measure the effect of treatment on an aggregate of endpoints of various importance. Inferences from composite endpoints are strongest in the rare situations in which (1) the component endpoints are of similar patient-importance, (2) the endpoints that are more important occur with at least similar frequency to those that are less important, and (3) strong biologic rationale supports results that, across component endpoints, show similar relative risks with sufficiently narrow confidence intervals.

Computer decision support system
A strategy for changing clinician behavior. Computer-based information systems used to integrate clinical and patient information and provide support for decision making in patient care. In clinical decision support systems (CDSSs) that are computer based, detailed individual patient data are entered into a computer program and are sorted and matched to programs or algorithms in a computerized database, resulting in the generation of patient-specific assessments or recommendations. CDSSs can have the following purposes: alerting, reminding, critiquing, interpreting, predicting, diagnosing, and suggesting. See also Clinical decision support system.

Computer simulation
A computer model that uses patient demographics, risk factors, history items, and symptoms to diagnose diseases and other conditions. Computer simulations may not be more accurate than clinical opinion.

Randomization is concealed if the person who is making the decision about enrolling a patient is unaware of whether the next patient enrolled will be entered in the intervention or control group (using techniques such as central randomization or sequentially numbered opaque, sealed envelopes). If randomization is not concealed, patients with better prognoses may tend to be preferentially enrolled in the active intervention arm, resulting in exaggeration of the apparent benefit of intervention (or even falsely concluding that the intervention is efficacious). See also Blind.

The basic building blocks of theory.

Conceptual framework
An organization of interrelated ideas or concepts that provides a system of relationships between those ideas or concepts.

Conditional probabilities
The probability of a particular state, given another state (i.e., the probability of A, given B).

Confidence interval
Range between two values within which it is probable that the true value lies for the whole population of patients from which the study patients were selected.

Conflict of interest
A situation in which an individual or group is involved in multiple interests (concerns), and one or more interests could possibly affect the motivation for an action or interpretation regarding another interest. Also, within the biomedical research and publishing enterprise, these conflicts may occur when investigators, authors, institutions, reviewers, and/or editors have financial or nonfinancial relationships with other persons or organizations (eg, study sponsors) or personal investments in research projects or the outcomes of projects that may inappropriately influence their interpretation or actions. Conflicts of interest can lead to biased design, conduct, analysis, and interpretation of study results.

1. A factor that distorts the true relationship of the study variable of interest by virtue of also being related to the outcome of interest. Confounders are often unequally distributed among the groups being compared. Randomized studies are less likely to have their results distorted by confounders than are observational studies. 2. A factor that is associated with the outcome of interest and is differentially distributed in patients exposed and unexposed to the outcome of interest.

Confusion Assessment Method
An assessment instrument that screens for presence or absence of delirium but does not assess the severity of the condition. For more information, see the following article for the instrument: Inouye SK, van Dyck CH, Alessi CA, et al. Clarifying confusion: the confusion assessment method. A new method for detection of delirium. Ann Intern Med. 1990;113(12):941-948. [PMID: 2240918]

Conscious sedation
Administering sedatives with or without analgesics to induce a mildly sedated state (“twilight sleep”) that allows the patient to tolerate unpleasant procedures while avoiding the need for intubation and mechanical ventilation.

Consecutive sample
A sample in which all potentially eligible patients seen over a period of time are enrolled. See also Case series.

Used interchangeably with coherence.

Construct validity
A construct is a theoretically derived notion of the domain(s) we wish to measure. An understanding of the construct will lead to expectations about how an instrument should behave if it is valid. Construct validity therefore involves comparisons between measures and examination of the logical relationships, which should exist between a measure and characteristics of patients and patient groups.

Occurs when participants in either the experimental or control group receive the intervention intended for the other arm of the study.

Continuous variable
A variable that can theoretically take any value and in practice can take a large number of values with small differences between them (eg, height). Continuous variables are also sometimes called interval data.

Control group
A group that does not receive the experimental intervention. In many studies, the control group receives either usual care or a placebo.

Convenience sample
Individuals or groups selected at the convenience of the investigator or primarily because they were available at a convenient time or place.

The over-representation of randomized controlled trials comparing specific interventions rather than other available interventions.

Corollary orders
Orders that are needed to detect or ameliorate adverse reactions.

The magnitude of the relationship between two different variables or phenomena.

Correlation coefficient
A numerical expression of the magnitude and direction of the relationship between two variables, which can take values from –1.0 (perfect negative relationship) to 0 (no relationship) to 1.0 (perfect positive relationship).

Cost analysis
An economic analysis in which only costs of various alternatives are compared. This comparison informs only the resource-use half of the decision (the other half being the expected outcomes).

Cost-benefit analysis
An economic analysis in which both the costs and the consequences (including increases in the length and quality of life) are expressed in monetary terms.

Cost-effectiveness acceptability curve
The cost-effectiveness acceptability is plotted on a graph that relates the maximum one is willing to pay for a particular treatment alternative (eg, how many dollars one is willing to pay to gain 1 life-year) on the x-axis to the probability that a treatment alternative is cost-effective compared with all other treatment alternatives on the y-axis. The curves are generated from uncertainty around the point estimates of costs and effects in trial-based economic evaluations or uncertainty around values for variables used in decision analytic models. As one is willing to pay more for health outcomes, treatment alternatives that initially might be considered unattractive (eg, a high cost per life-year saved) will have a higher probability of becoming more cost-effective. Cost-effectiveness acceptability curves are a convenient method of presenting the effect of uncertainty on economic evaluation results on a single figure instead of through the use of numerous tables and figures of sensitivity analyses.

Cost-effectiveness analysis
An economic analysis in which the consequences are expressed in natural units. Examples include cost per life saved or cost per unit of blood pressure lowered.

Cost-effectiveness efficiency frontier
The cost and effectiveness results of each treatment alternative from an economic evaluation can be graphed on a figure known as the cost-effectiveness plane. The cost-effectiveness plane plots cost on the vertical axis (i.e., positive infinity at the top and negative infinity and the bottom) and effects such as life-years on the horizontal axis (i.e., negative infinity at the far left and positive infinity at the far right). One treatment alternative such as usual care is plotted at the origin (i.e., 0, 0), and all other treatment alternatives are plotted relative to the treatment at the origin. Treatment alternatives are considered dominated if they have both higher costs and lower effectiveness relative to any other. Line segments can be drawn connecting the nondominated treatment alternatives and the combination of line segments that join these nondominated treatment alternatives is referred to as the cost-effectiveness efficiency frontier. Constructed in this way, any treatment alternative that lies above the cost-effectiveness efficiency frontier is considered to be inefficient (dominated) by a treatment alternative or combination of alternatives on the efficiency frontier.

Cost-minimization analysis
An economic analysis conducted in situations in which the consequences of the alternatives are identical, and the only issue is their relative costs.

Cost-to-charge ratio
Where there is a systematic deviation between costs and charges, an economic analysis may adjust charges using a cost-to-charge ratio to approximate real costs.

Cost-utility analysis
A type of economic analysis in which the consequences are expressed in terms of life-years adjusted by peoples’ preferences. Typically, one considers the incremental cost per incremental gain in quality-adjusted life years (QALYs). See also Quality-adjusted life-year.

Clinicians’ emotional reactions to patients.

Courvoisier sign
A palpable, nontender gallbladder in a patient with jaundice.

Cox regression model
A regression technique that allows adjustment for known differences in baseline characteristics between intervention and control groups applied to survival data. See also Adjusted analysis.

In qualitative research, a term used instead of validity to reflect whether the investigators engaged thoroughly and sensitively with the material and whether the investigators’ interpretations are credible. Signs of credibility can be found not only in the procedural descriptions of methodology but also through an assessment of the coherence and depth of the findings reported.

Credible intervals
Bayesian analogy to confidence intervals.

Critical theory
A qualitative research tradition focused on understanding the nature of power relationships and related constructs, often with the intention of helping to remedy systemic injustices in society.

A strategy for changing clinician behavior. A decision support approach in which the computer evaluates a clinician’s decision and generates an appropriateness rating or an alternative suggestion.

Cronbach α coefficient
Cronbach α is an index of reliability homogeneity or internal consistency of items on a measurement instrument. The Cronbach α rises with the magnitude of the interitem correlation and with the number of items.

Crossover study
A study design in which all patients are switched, in a specified or random order, to the alternate intervention after a specified period of time. See also Before-after design.

Cross-product ratio
A ratio of the odds of an event in an exposed group to the odds of the same event in a group that is not exposed.

Cross-sectional study
The observation of a defined population at a single point in time or during a specific time interval. Exposure and outcome are determined simultaneously.

Cultural competency
Ability to interact effectively with people of different cultures.

Cultural diversity
Variety of human cultures in a specific setting or region or in the world as a whole.

Culturally and Linguistically Appropriate Services (CLAS) standards
The US government mandates that health care organizations that receive Medicare reimbursements make their practices culturally and linguistically accessible. The 14 CLAS standards are organized by the themes of culturally competent care (standards 1-3), language access services (standards 4-7), and organizational supports for cultural competence (standards 8-14). For more information, see the following Web site for the standards:

Current Procedural Terminology (CPT)
A formal classification of diagnostic and therapeutic procedures performed by physicians and other health care professionals, published in annual revisions by the American Medical Association. Each procedure is assigned a 5-digit code. For more information, see the following Web site for the terminology:

Curtain sign
Also known as "enhanced ptosis" or "paradoxic ptosis", the curtain sign is usually observed in patients with some initial ptosis. The patient looks straight ahead and refrains from blinking. The examiner holds one eye open, which results in the other lid starting to droop more (like a curtain falling).

See stereotactic radiosurgery.

Cystic fibrosis
A hereditary disease (also known as mucoviscidosis) that involves difficulty breathing from frequent lung infections. Usually appears in early childhood and is more common in white populations.
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