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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 June 2014.
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P

P value
The probability that results as extreme as or more extreme than those observed would occur if the null hypothesis were true and the experiment were repeated over and over. A P value <0.05 means that there is a less than 1 in 20 probability that, on repeated performance of the experiment, the results as extreme as or more extreme than those observed would occur if the null hypothesis were true. See also Probability.

Pain Assessment in Advanced Dementia (PAIN-AD)
Scale used to assess pain in patients with Alzheimer disease and other forms of dementia. For more information, see the following article for the scale: Warden V, Hurley AC, Volicer L. Development and psychometric evaluation of the Pain Assessment in Advanced Dementia (PAINAD) scale. J Am Med Dir Assoc. 2003;4(1):9-15. [PMID: 12807591]

Pain crisis
An event in which the patient reports severe, uncontrolled pain that causes the patient, family, or both severe distress. The pain may be acute in onset or may have progressed gradually to an intolerable threshold (as determined by the patient), but requires immediate intervention.

Palliate
Palliative care or treatment is a set of actions taken for patients in whom cure is unlikely. Stedman's defines palliative as mitigating or reducing the severity of symptoms without reducing the underlying disease. These actions are often multiple and can include family members and significant others.

Palliative care
Care focused primarily on relieving pain and physical symptoms, enhancing psychosocial supports, and assisting patients and families to make the best possible decisions in the face of serious, potentially life-threatening illness.

Palliative care service
Department or team at a health care facility that provides palliative and end-of-life care. See also palliative care.

Palliative chemotherapy
Chemotherapy administered without curative intent, with the goal of decreasing tumor load and possibly increasing life expectancy.

Palliative Excellence in Alzheimer Care Efforts (PEACE) program
The Palliative Excellence in Alzheimer Care Efforts (PEACE) program incorporates concepts of advance care planning, patient-centered care, family support, and a palliative care focus on Alzheimer disease management from diagnosis through terminal care.

Palliative Performance Scale
A measurement tool that uses 5 observer-rated domains to assess the functional status of a patient: ambulation, activity level, self-care, intake, and level of consciousness. Provides correlates with estimated median survival in days. For more information, see the following article for the scale: Anderson F, Downing GM, Hill J, Casorso L, Lerch N. Palliative performance scale (PPS): a new tool. J Palliat Care. 1996;12(1):5-11. [PMID: 8857241].

Palliative Prognostic Index (PPI)
Defined by performance status, oral intake, edema, dyspnea at rest, and delirium; can help to predict whether patients will live longer than 3 or 6 weeks. For more information, see the following article for the index: Morita T, Tsunoda J, Inoue S, Chihara S. The Palliative Prognostic Index: a scoring system for survival prediction of terminally ill cancer patients. Support Care Cancer. 1999;7(3):128-133. [PMID: 10335930].

Palliative Prognostic Score
Score assigns numerical points to anorexia, dyspnea, Karnofsky performance status (see also Karnofsky performance status), total white blood cell count, and percentage of lymphocytes on white cell differential. Total scores range from 0 to 17.5 and help to predict survival. Patients can be segmented into 3 risk groups, A, B, and C, based on their total scores, and this grouping correlates with whether patients will live longer than 30 days. For more information, see the following Web site for the score: http://www.mcw.edu/fastFact/ff_124.htm.

Palliative sedation
When terminally ill, conscious patients experience intolerable symptoms that cannot be relieved even by expert palliative care, palliative sedation involves administering sedatives to relieve suffering in doses that may induce unconsciousness.

Palliative sedation to unconsciousness
The goal of this form of sedation is to cause unconsciousness without the intent of shortening the patient’s life. For example, in massive external hemorrhage in a terminally ill patient, relieving the patient’s distress might require making the patient unconscious so that he/she is unaware of the bleeding.

Palmar erythema
A reddening of the palms, especially below the thumb and little finger, sparing the palm's center.

Palpation
The act of a clinician touching a patient to determine the condition of an underlying organ.

Paracentesis
A surgical puncture of a bodily cavity with a trocar, aspirator, or other instrument usually to draw off an abnormal effusion for diagnostic or therapeutic purposes. Paracentesis can also be done as a therapeutic procedure when large volumes of fluid are removed to provide the patient relief from symptoms.

Parasitemia
1. The quantity of Plasmodium parasites in the blood, used as a proxy of the severity of infection. 2. The presence of Plasmodium parasites in the blood. Fever with parasitemia is a pracitcal and widely used definition for acute malaria.

Parenchyma
The essential tissue of an organ or an abnormal growth as distinguished from its supportive framework.

Paroxysmal cough
A paroxysm is a series of coughs during a single expiration; these episodes often occur in groups throughout the day and night, with patients experiencing few symptoms between paroxysms. A cough paroxysm causes low lung volumes, leading to a vigorous inspiration that may result in a whoop, particularly in infants and children, in whom the caliber of the trachea is smaller. The paroxysmal stage of pertussis begins during the second week of illness.

Partial verification bias
Occurs when only a selected sample of patients who underwent the index test is verified by the reference standard, and that sample is dependent on the results of the test. For example, patients with suspected coronary artery disease whose exercise test results are positive may be more likely to undergo coronary angiography (the reference standard) than those whose exercise test results are negative. See also Bias.

Pastia sign
A scarlatiniform ("scarlet fever") rash in the antecubital fossae is one of the signs for streptococcal pharyngitis.

Patient expected event rate
The probability of the occurrence of the endpoint or outcome of interest in the patient group of which the individual under consideration is representative.

Patient preferences
The relative value that patients place on various health states. Preferences are determined by values, beliefs, and attitudes that patients bring to bear in considering what they will gain—or lose—as a result of a management decision. Explicit enumeration and balancing of benefits and risks that is central to evidence-based clinical practice brings the underlying value judgments involved in making management decisions into bold relief.

Patient-important outcomes
Outcomes that patients value directly. This is in contrast to surrogate, substitute, or physiologic outcomes that clinicians may consider important. One way of thinking about a patient-important outcome is that, were it to be the only thing that changed, patients would be willing to undergo a treatment with associated risk, cost, or inconvenience. This would be true of treatments that ameliorated symptoms or prevented morbidity or mortality. It would not be true of treatments that lowered blood pressure, improved cardiac output, improved bone density, or the like, without improving the quality or increasing the length of life.

Patient-mediated interventions
A strategy for changing clinician behavior. Any intervention aimed at changing the performance of health care professionals through interactions with, or information provided by or to, patients.

Pediatric Advanced Care Team (PACT)
A group of medical professionals who work to enhance the quality of life and reduce the suffering of children and teens who have been diagnosed as having life-threatening illnesses.

Pedigree
A diagram depicting heritable traits across 2 or more generations of a family.

Peek sign
A sign for myasthenia gravis elicited by having the patient close their eyelids to hold them in apposition. Despite effort to keep them closed, the lids gradually separate and the examiner will be able to see the sclera in a positive sign.

Peptic ulcer disease
Peptic ulcer disease refers to duodenal or gastric ulceration.

Percutaneous endoscopic gastrostomy (PEG)
A procedure in which a tube is placed through the skin and subcutaneous tissue into a patient’s stomach as a means of providing liquid artificial nutrition to the patient when he/she is unable to eat.

Performance criteria
Concerns how interventions are performed without regard to whether they should be performed. An example would be the acceptable range of results reported for reference cholesterol samples sent to clinical laboratories.

Pericardial effusion
Accumulation of fluid within the pericardial sac.

Periumbilical
Adjacent to the navel.

Per-protocol analysis
An analysis restricted to patients who adhered to their assigned treatment in a randomized trial (omitting patients who dropped out of the study or for other reasons did not actually receive the planned intervention). This analysis can provide a misleading estimate of effect because all patients randomized are no longer included, raising concerns about whether important unknown factors that influence outcome are equally distributed across comparison groups.

Pertussis
An infectious disease characterized by a severe, persistent cough. Symptoms of pertussis include paroxysmal cough, posttussive emesis, and inspiratory whoop. Also known as whooping cough.

Phalen sign
Paresthesias in the distribution of the median nerve when the patient flexes both wrists 90 degrees for 60 seconds.

Phase I studies
Studies often conducted in normal volunteers that investigate a drug’s physiologic effect and evaluate whether it manifests unacceptable early toxicity.

Phase II studies
Initial studies on patients that provide preliminary evidence of possible drug effectiveness.

Phase III studies
Randomized controlled trials designed to test the magnitude of benefit and harm of a drug.

Phase IV studies
Studies conducted after the effectiveness of a drug has been established and the drug marketed, typically to establish the frequency of uncommon or unanticipated toxic effects.

Phenomenology
In qualitative research, an approach to inquiry that emphasizes the complexity of human experience and the need to understand the experience holistically as it is actually lived.

Phenotype
The observable characteristics of a cell or organism, usually being the result of the product coded by a gene (genotype).

Phi statistic (φ)
A measure of chance-independent agreement calculated by the following formula: [square root of (OR – 1)]/[square root of (OR + 1)].

Physician Orders for Life-Sustaining Treatment (POLST)
Preprinted and signed physician orders specifying treatment instructions in the event of serious illness, including cardiopulmonary resuscitation, levels of medical intervention, antibiotics, intravenous fluids, and feeding tubes. For more information, see the following Web site for the orders: http://www.ohsu.edu/polst.

Physician-assisted suicide (PAS)
The prescribing of lethal medications for patients to self-administer.

PICO 
A method for answering clinical questions.

Placebo
A biologically inert substance (typically a pill or capsule) that is as similar as possible to the active intervention. Placebos are sometimes given to participants in the control arm of a drug trial to help ensure that the study is blinded.

Placebo effect
The impact of an intervention independent of its biological effect.

Plasmodium falciparum
The most virulent species of Plasmodium and is found worldwide. Patients infected with P falciparum may manifest life-threatening malarial syndromes such as cerebral malaria, which is portended by the onset of altered consciousness, seizures, or nonfocal dysfunction of the central nervous system.

Plasmodium knowlesi
A species of Plasmodium and an emerging human pathogen only documented in Southeast Asia.

Plasmodium malariae
A species of Plasmodium resulting in a chronic, indolent infection. It has widespread but focal geographic distribution.

Plasmodium ovale
A species of Plasmodium with widespread but focal geographic distribution. Patients may experience recurrent fevers.

Plasmodium vivax
A species of Plasmodium endemic in tropical areas outside of sub-Saharan Africa and accounts for a large fraction of infections in Latin America and South and Southeast Asia. Patients may experience recurrent fevers.

Pleural effusion
Fluid in the pleural cavity. It indicates the presence of a disease that may be pulmonary, pleural, or extrapulmonary in origin.

Point estimate
The single value that best represents the value of the population parameter.

Polymorphism
The existence of 2 or more variants of a gene, occurring in a population, with at least 1% frequency of the less common variant. See also Mutation.

Pooled estimate
Estimate based on combining data from 2 or more samples.

Population stratification
Describes the situation in which a population may be composed of multiple sub-groups of different ethnicity; case and control group differences in the mix can confound the comparison and lead to spurious genetic associations.

Positive predictive value
See Predictive value.

Positive study
1. A study with results that are consistent with the researchers’ hypotheses. 2. A study with results that show a difference that investigators interpret as beyond the play of chance.

Post–acute palliative care settings
When a patient receiving palliative care leaves the hospital but cannot go home, post–acute care options usually include inpatient hospice, nursing home with or without hospice, or residential care with hospice.

Posterior distribution
In Bayesian analysis, the probability distribution obtained by mixing prior knowledge with data.

Posttest odds
The odds of the target condition being present after the results of a diagnostic test are available.

Posttest probability
The probability of the target condition being present after the results of a diagnostic test are available.

Posttraumatic growth
Positive changes in interpersonal relationships, sense of self, and philosophy of life subsequent to direct experience of a traumatic event that shakes the foundation of an individual’s worldview.

Posttraumatic stress disorder (PTSD)
Severe anxiety disorder that can develop after exposure to any event that results in psychological trauma, including symptoms of re-experiencing, avoidance, and increased arousal that last for more than 1 month.

Posttussive emesis
Vomiting after coughing. A symptom of pertussis.

POUNDing
Mnemonic used to assess the likelihood of migraine. The clinician asks the following questions: Is it a Pulsating headache? Does it last between 4-72 hOurs without medication? Is it ever Unilateral? Is there Nausea? Is it Disabling?

Power
The ability of a study to reject a null hypothesis when it is false (and should be rejected). It is linked to the adequacy of the sample size: if a sample size is too small, the study will have insufficient power to detect differences between groups, if differences exist.

Predictive value
Two categories: Positive predictive value—the proportion of people with a positive test result who have the disease; negative predictive value—the proportion of people with a negative test result and who are free of disease.

Pre-processed
A process whereby someone has reviewed the literature and chosen only the methodologically strongest studies.

Presbycusis
Sensorineural hearing loss related to aging caused by the degeneration of the hair cells in the organ of Corti.

Pretest odds
The odds of the target condition being present before the results of a diagnostic test are available.

Pretest probability
The probability of the target condition being present before the results of a diagnostic test are available.

Prevalence
Proportion of persons affected with a particular disease at a specified time. Prevalence rates obtained from high-quality studies can inform pretest probabilities.

Prevent
A preventive maneuver is an action that decreases the risk of a future event or the threatened onset of disease. Primary prevention is designed to stop a condition from developing. Secondary prevention is designed to stop or slow progression of a disease or disorder when patients have a disease and are at risk for developing something related to their current disease. Often, secondary prevention is indistinguishable from treatment. An example of primary prevention is vaccination for pertussis. An example of secondary prevention is administration of an antiosteoporosis intervention to women with low bone density and evidence of a vertebral fracture to prevent subsequent fractures. An example of tertiary prevention is a rehabilitation program for patients experiencing the adverse effects associated with a myocardial infarction.

Primary care
Medical care provided by the clinician of first contact for the patient. Typically, the primary care physician is a general practitioner, family practitioner, primary care internist, or primary care pediatrician. Primary care may also be administered by health professionals other than physicians, notably specially trained nurses (nurse practitioners) and paramedics. Usually, a general practitioner, family practitioner, nurse practitioner, or paramedic provides only primary care services, but an individual with specialty qualifications may provide primary care, alone or in combination with referral services. Thus, it is the nature of the contact (first vs. referred) that determines the care designation rather than the qualifications of the practitioner. See also Referred care.

Primary care clinician
Medical professional with whom the patient has regular contact and by whom the patient may be referred to a specialist.

Primary care setting
Medical care facility that offers first contact health care only. Patients requiring specialized medical care are referred elsewhere. Some primary care centers provide a mixture of primary and referred care. Thus, it is the nature of the service provided (first contact) rather than the setting per se that distinguishes primary from more advanced levels of care. See also Primary care; Referred care; Tertiary care center.

Primary open-angle glaucoma (POAG)
The predominant form of glaucoma in the United States. In POAG, as compared with closed-angle glaucoma, the iridocorneal angle appears open on clinical examination.

Primary studies
Studies that collect original data. Primary studies are differentiated from synopses that summarize the results of individual primary studies and they are different from systematic reviews that summarize the results of a number of primary studies.

Priors (informed)
The representation of external (prior) knowledge about the intervention effects or degree of heterogeneity that is incorporated in Bayesian analysis.

Priors (noninformative)
In Bayesian analysis, the assumption that nothing is known about the intervention effect or degree of heterogeneity prior to looking at the available data.

Probability
Quantitative estimate of the likelihood of a condition existing (as in diagnosis) or of subsequent events (such as in an intervention study). See also P value.

Profile of Mood States (POMS)
Test designed to measure 6 mood states: confusion, tension, depression, anger, vigor, and fatigue. Individuals are scored for each trait according to their responses to certain statements that include keywords such as unhappy, tense, careless, and cheerful. For each statement, individuals state how they feel at that moment, or how they felt during the previous day, few days, or week, by choosing 1 of 5 responses: not at all, a little, moderately, quite a lot, or extremely. For more information, see the following Web site for the test: http://downloads.mhs.com/poms/poms-tech-brochure.pdf.

Prognosis
The prospect of survival and/or recovery from a disease as anticipated from the usual course of that disease or indicated by special features of the case.

Prognostic factors
Patient or study participant characteristics that confer increased or decreased risk of a positive or adverse outcome.

Prognostic indicator
Symptom, sign, or characteristic associated with likelihood of survival and/or recovery from a disease.

Prognostic study
A study that enrolls patients at a point in time and follows them forward to determine the frequency and timing of subsequent events.

Program for All-Inclusive Care of the Elderly (PACE)
Comprehensive geriatric medicine assessment and treatment program with home care components.

Proportionate palliative sedation
In proportionate palliative sedation, the level of sedation is increased until symptoms are relieved; the lowest level of sedation is used that will relieve symptoms. In some cases, symptom relief requires making the patient unconscious.

Provider adherence
Extent that health care providers carry out the host of diagnostic tests, monitoring equipment, interventional requirements, and other technical specifications that define optimal patient management.

Pseudoaddiction
Behaviors typically associated with addiction (demand for specific medications and doses, anger and irritability, poor cooperation, or disturbed interpersonal relationships) that may emerge when an individual is not receiving adequate pain relief. Once pain is relieved, these behaviors cease.

Psychomotor agitation
A series of unintentional and purposeless motions that stem from mental tension and anxiety of an individual (eg, pacing around a room, wringing one’s hands).

Psychotherapy
Treatment of mental or emotional disorder or of related bodily ills by psychological means.

Publication bias
Occurs when the publication of research depends on the direction of the study results and whether they are statistically significant. See also Bias.

Puddle sign
A maneuver to detect ascites that is not currently recommended. To elicit the finding, the patient must prop them selves up on their hands and knees, while the examiner reaches underneath the abdomen to percuss.

Pulmonary edema
Abnormal accumulation of fluid in the lungs.

Pulmonary rattle
A synonym for death rattle, a sign of retained respiratory secretions displayed by many dying patients.

Pulsus paradoxus
An exaggeration of the normal inspiratory decrease in blood pressure.

Purposeful sampling
In qualitative research, a type of nonprobability sampling in which theory or personal judgment guide the selection of study participants who will be most representative of the population. Depending on the topic, examples include (1) maximum variation sampling, to document range or diversity; (2) extreme or deviant case sampling, in which one selects cases that are opposite in some way; (3) typical or representative case sampling, to describe and illustrate what is typical and common in terms of the phenomenon of interest; (4) critical sampling, to make a point dramatically; and (5) criterion sampling, in which all cases that meet some predetermined criteria of importance are studied.

Purulent exudate
Pus; a type of exudate, or fluid from a wound, that is high in protein content and cellular debris. Typically ranges in color from yellow to green to brown. Considered a classic sign of wound infection.

Pyelonephritis
Bacterial or fungal invasion of the kidney causing tubular cell necrosis and inflammation of both the parenchyma and the lining of its renal pelvis. Chronic pyelonephritis involves pelvicaliceal inflammation, fibrosis, and deformity of the kidney.

Pyrexia
Abnormal elevation of body temperature, fever.

Pyuria
The presence of pus in urine.
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