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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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A

ABCD framework
Dignity-conserving care has been described within an ABCD framework: A for attitude, underscoring the importance of care provider perception and the extent to which this can provide the patient a sense of affirmation and continued worth; B for behavior, denotes the various mannerisms and approaches that convey respect and acknowledgment of the patient’s personhood; C for compassion, predicated on an awareness of the patient as a person; and D for dialogue, underscores the importance of conversations that are able to acknowledge issues of personhood. (See also Chapter 27, Dignity-Conserving Care—A New Model for Palliative Care.)

Absolute difference
The absolute difference in rates of good or harmful outcomes between experimental groups (experimental group risk, or EGR) and control groups (control group risk, or CGR), calculated as the risk in the control group minus the risk in the experimental group (CGR – EGR). For instance, if the rate of adverse events is 20% in the control group and 10% in the treatment group, the absolute difference is 20% – 10% = 10%.

Absolute risk
The risk of an event (eg, if 10 of 100 patients have an event, the absolute risk is 10% expressed as a percentage, or 0.10 expressed as a proportion).

Absolute risk increase
The absolute arithmetic difference in risk of harmful outcomes between experimental groups (experimental group risk, or EGR) and control groups (control group risk, or CGR), calculated as risk of harmful outcome in experimental group minus rate of harmful outcome in control group (EGR – CGR). Typically used to describe a harmful exposure or intervention (eg, if the rate of adverse outcomes is 20% in treatment and 10% in control, the absolute risk increase would be 10% expressed as a percentage and 0.10 expressed as a proportion). See also Absolute risk reduction; Number needed to harm.

Absolute risk reduction
The absolute difference (risk difference) in risks of harmful outcomes between experimental groups (experimental group risk, or EGR) and control groups (control group risk, or CGR), calculated as the risk of harmful outcome in the control group minus the risk of harmful outcome in the experimental group (CGR – EGR). Typically used to describe a beneficial exposure or intervention (eg, if 20% of patients in the control group have an adverse event, as do 10% among treated patients, the ARR or risk difference would be 10% expressed as a percentage or 0.10 expressed as a proportion).

Academic detailing
A strategy for changing clinician behavior. Use of a trained person who meets with professionals in their practice settings to provide information with the intent of changing their practice. The pharmaceutical industry frequently uses this strategy, to which the term detailing is applied. Academic detailing is such an interaction initiated by an academic group or institution rather than the pharmaceutical industry.

Active alternatives
The set of diagnoses that can plausibly explain a patient’s presentation. See also Differential diagnosis.

Activities of daily living (ADLs)
ADLs are self-care activities of dressing, bathing, transferring, ability to ambulate, eating, and continence. ADLs are more basic than IADLs (instrumental activities of daily living) that include shopping, housework, accounting, food preparation, and transportation.

Acute Physiology and Chronic Health Evaluation (APACHE) II or III
A classification system that measures the severity of disease for adult patients admitted to intensive care units. For more information, see the following article for the classification system: Barie PS, Hydo LJ, Fischer E. Comparison of APACHE II and III scoring systems for mortality prediction in critical surgical illness. Arch Surg. 1995;130(1):77-82. [PMID: 7802581]

Addiction
Compulsive physical or physiologic need for and use of a habit-forming substance characterized by its misuse for purposes other than the one for which it was prescribed and despite negative consequences. Addiction is distinguished from tolerance (the patient requires increasing dosage to achieve the same analgesic effect) and from dependence (the patient requires continued dosing to prevent well-defined physiologic symptoms on withdrawal). See also Pseudoaddiction.

Additive
Describes any trait that increases proportionately in expression when comparing those with no copy, 1 copy, or 2 copies of that allele, ie, those with 1 copy of the allele show more of the trait than those without, and in turn, those with 2 copies show more of the trait than those with 1 copy.

Adherence
Extent to which patients carry out health care recommendations, or the extent to which health care providers carry out the diagnostic tests, monitoring equipment, interventional requirements, and other technical specifications that define optimal patient management.

Adjusted analysis
An adjusted analysis takes into account differences in prognostic factors (or baseline characteristics) between groups that may influence the outcome. For instance, when comparing an experimental and control intervention, if the experimental group is on average older, and thus at higher risk of an adverse outcome than the control group, the analysis adjusted for age will show a larger treatment effect than the unadjusted analysis. See also Cox regression model.

Adjusted indirect comparison
A statistical technique that permits comparison between 2 interventions that have not been compared directly (head-to-head) but have both been compared to the same third comparator. This method preserves the principle of randomization.

Adjuvant
Agent used to enhance the action of the main treatment. In palliative care, term used to describe different drugs and classes of drugs that may enhance the effects of opioids or nonsteroidal anti-inflammatory drugs, or of palliative chemotherapeutic agents.

Advance care directives
Instructions that are meant to ensure that patients’ wishes concerning end-of-life care are respected and carried out, even when the patients are no longer able to speak for themselves.

Advance care planning
The process by which patients, together with their families and health care practitioners, consider their values and goals and articulate preferences for future care.

Advance directives
A synonym for advance care directives (ACDs), instructions that are meant to ensure that patients’ wishes concerning end-of-life care are respected and carried out, even when the patients are no longer able to speak for themselves.

Aid to Capacity Evaluation (ACE)
A screening instrument for medical decision-making capacity. ACE uses 8 questions modified to the patient's problem and treatment choices. See http://capm.wikispaces.com/file/view/ACE.pdf/107065929/ACE.pdf.

AIDS-related opportunistic infections
Infections due to pathogenic microbial agents that have the “opportunity” to develop in patients with compromised immune systems. These agents usually do not cause disease in patients with intact immune systems.

Alerting systems
A strategy for changing clinician behavior. A type of computer decision support system that alerts the clinician to a circumstance that might require clinical action (eg, a system that highlights out-of-range laboratory values). See also Reminder systems.

Algorithm
An explicit description of an ordered sequence of steps with branching logic that can be applied under specific clinical circumstances. The logic of an algorithm is as follows: if a, then do x; if b, then do y; etc.

Allele
One of several variants of a gene, usually referring to a specific site within the gene.

Alpha level
The probability of erroneously concluding there is a difference between comparison groups when there is in fact no difference (type I error). Typically, investigators decide on the chance of a false-positive result they are willing to accept when they plan the sample size for a study (eg, investigators often set alpha level at 0.05).

Alvarado model
The Alvarado model is a clinical decision rule for diagnosing appendicitis. This model uses the MANTRELS mnemonic to examine 8 findings from the medical history or the examination, and the resulting score provides guidance on whether to operate in the setting of suspected appendicitis. Of 10 potential points, patients with a score of 7 or higher are considered “positive” and are more likely to have appendicitis. The various components are Migration (1 point), Anorexia-acetone (1), Nausea-vomiting (1), Tenderness in RLQ (2), Rebound pain (1), Elevation of temperature (1), Leukocytosis (2), and Shift to the left of normal WBC count (1). See Table 5-5 in The Rational Clinical Examination.

Alzheimer disease
A degenerative brain disease of unknown cause that results in progressive memory loss, impaired thinking, disorientation, and changes in personality and mood and that leads to a profound decline in cognitive and physical functioning. The most common form of dementia.

American Joint Committee on Cancer classifications
The American Joint Committee on Cancer classifications are used by medical professionals to select the most effective treatment, determine prognosis, and continue evaluating cancer control measures. The classifications involve clinical staging, pathologic staging, restaging, and the tumor-node-metastasis (TNM) staging system. For more information, see the following Web site for the classifications: http://www.cancerstaging.org. See also UICC-TNM.

American Spinal Injury Association Impairment Scale
The extent of spinal injury, defined by the American Spinal Injury Association Impairment Scale (modified from the Frankel classification), is categorized as follows: A-Complete: no sensory or motor function is preserved in sacral segments S4-S5; B-Incomplete: sensory, but not motor, function is preserved below the neurologic level and extends through sacral segments S4-S5; C-Incomplete: motor function is preserved below the neurologic level, and most key muscles below the neurologic level have muscle strength grade less than 3; D-Incomplete: motor function is preserved below the neurologic level, and most key muscles below the neurologic level have muscle grade greater than or equal to 3; and E-Normal: sensory and motor functions are normal. For more information, see the following Web site for the scale: http://www.asia-spinalinjury.org/publications/2006_Classif_worksheet.pdf.

Amoss sign
In patients with severe meningeal irritation, the patient may spontaneously assume the tripod position (also called Amoss sign or Hoyne sign), sitting on the edge of the bed with the knees and hips flexed, the back arched lordotically, the neck extended, and the arms brought back to support the thorax.

Amyotrophic lateral sclerosis
A progressive neurodegenerative disorder of unknown cause and pathogenesis, with no known cure. It is characterized by progressive loss of motor neurons.

Analgesia
A state in which painful stimuli are moderated such that, although still perceived, they are no longer painful; insensibility to pain.

Analgesics, opioid
Medications that help to decrease perception of pain, decrease reaction to pain, and increase tolerance to pain.

Anchor
An independent standard that is itself interpretable and at least moderately correlated with the instrument being explored. The anchor is usually designed to establish a minimum important difference (MID) in change.

Ankle-brachial index
The ratio of the highest ankle systolic pressure divided by the highest brachial systolic pressure. This is a commonly accepted reference standard for diagnosising peripheral arterial disease because it is highly sensitive and specific.

Apnea
When breathing temporarily stops, particularly during sleep. See also obstructive sleep apnea.

Apnea test
The last clinical test performed during the examination for brain death. A positive test result requires discontinuation of mechanical ventilation and observation for the absence of any respiratory effort in the presence of an adequate stimulus for respiratory drive.

Apnea-hypopnea index (AHI)
The number of apnea or hypopnea events per hour of sleep. This index is used to evaluate the severity of obstructive sleep apnea in patients.

Arrhythmias, cardiac
Any irregularity in cardiac rate or rhythm.

Arthralgia
Joint pain.

Arthritis, infectious
The purulent invasion of a joint by an infectious agent that produces arthritis (ie, septic arthritis).

Arthritis, rheumatoid
A chronic, systemic inflammatory disorder that attacks the joints producing an inflammatory synovitis and is characterized by pain, stiffness, inflammation, swelling, and sometimes destruction of joints.

AST:ALT ratio (AAR)
Aspartate aminotransferase:alanine aminotransferase ratio. A scoring index used to calculate the likelihood of cirrhosis; an AAR higher than 1 is associated with an increased likelihood of cirrhosis.

AST:platelet ratio index (APRI)
Aspartate aminotransferase:platelet ratio index. A scoring index used to calculate the likelihood of cirrhosis; an APRI higher than 2 is associated with an increased likelihood of cirrhosis. APRI = AST:platelet ratio index = (AST/upper limit of normal AST) x (100/platelet count [(x 103/µL)]).

Atelectasis
Loss of air in all or part of the lung (collapse).

Atrioventricular nodal reentry
A regular supraventricular tachycardia caused by a reentry circuit involving the atrioventricular node. The most frequent symptom is palpitations, often sensed by the patient in his or her neck.

Audiometry
A hearing test using individual tones of different frequencies (ranging from 250 to 8000 Hz) that are presented in a soundproof room at various intensities (ranging from 5 to 120 dB) to each ear.

Audit and feedback
A strategy for changing clinician behavior. Any written or verbal summary of clinician performance (eg, based on chart review or observation of clinical practice) during a period of time. The summary may also include recommendations to improve practice.

Aura
A symptom that heralds the onset of a migraine headache or a seizure. Typically, auras are visual phenomenon, but they may include any sensation or behavioral change that occurs shortly before the onset of the headache or seizure.

Autocorrelation
Occurs when the likelihood of an observation is not independent of its relationship with other observations. For example, autocorrelation occurs when a good day for a patient with chronic disease is more likely to follow a "good day" than a "bad day."

Autonomic dysfunction
Any disease or malfunction of the autonomic nervous system, producing symptoms such as orthostatic hypotension and gastroparesis.
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