Dictionary

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I-SquaredConceptI2 Statistic, Higgins I2

A statistic quantifying the percentage of total variation across studies in a meta-analysis attributable to genuine heterogeneity rather than chance.

ICD CodingTermICD Classification, Diagnosis Coding

An internationally standardised disease classification system maintained by the World Health Organization, used for documentation, billing, and epidemiological research.

Imaging AnalyticsTermRadiology Analytics, Medical Image Analysis

The application of computational analysis, including artificial intelligence, to interpret and extract clinically relevant information from medical images.

Imaging CentreTermImaging Center, Diagnostic Imaging Facility

A specialist facility dedicated to diagnostic imaging procedures, such as X-rays, CT, and MRI, often operating independently of a hospital.

Imaging DataTermRadiographic Data, Scan Data

Information derived from medical imaging techniques, such as radiographs, CT, or MRI, used to assess anatomical or functional disease changes.

Imaging OutcomeTermRadiographic Outcome, Scan-Based Outcome

A clinical outcome measure based on findings from radiological imaging, such as tumour size on a scan, assessing disease status or response.

Immediate OutcomeTermEarly Outcome, Near-Term Outcome

A clinical or economic outcome observed shortly after treatment, unlike a delayed outcome that only manifests after an extended period.

Immortal TimeConceptImmortal Person-Time, Guarantee-Time Period

A period of follow-up during which, due to how exposure groups were defined, a participant could not possibly have experienced the outcome.

Immortal Time BiasTermGuarantee-Time Bias, Survivor Treatment Selection Bias

A bias where a period of follow-up is misclassified so a participant cannot, by design, experience the outcome during it, inflating apparent benefit.

Immunisation ProgrammeTermImmunization Programme, Vaccination Programme

A coordinated public health effort to vaccinate a population against one or more infectious diseases according to a defined schedule.

ImmunogenicityTermImmune Response Potential, Anti-Drug Immune Response

The capacity of a biological therapy to provoke an immune response in the patient receiving it, potentially reducing effectiveness or causing adverse reactions.

Immunological ResponseTermImmune Response, Immunologic Response

A biomarker-based outcome measure indicating a change in immune system function or activity, such as antibody levels, following treatment.

Immunology EconomicsTermEconomics of Immunology, Immune Disease Economics

The application of health economic evaluation to conditions involving the immune system, covering autoimmune disease, immunodeficiency, and allergic conditions.

ImmunotherapyTermImmuno-Oncology Therapy, Immune Therapy

A category of cancer and other disease treatments harnessing or enhancing the body's own immune system to fight disease.

Immunotherapy CostTermImmuno-Oncology Cost, Cost of Immunotherapy

The expense of cancer treatments harnessing the body's immune system to fight cancer cells, generally priced substantially higher than conventional chemotherapy.

Immunotherapy EconomicsTermImmuno-Oncology Economics, Economics of Immunotherapy

The application of health economic evaluation to cancer immunotherapy, comparing substantial upfront cost against durable clinical responses observed in some patients.

Impact AnalysisTerm

An evaluation estimating the causal effect of a programme on its intended outcomes, comparing observed results against what would have occurred without it.

Impact AssessmentTermDecision Consequence Review, Consequence Evaluation

An evaluation of the anticipated or actual consequences of an assessment decision, covering patient outcomes, costs, and societal effects.

Impact EvaluationTermCausal Impact Study, Effect Evaluation

An evaluation estimating the causal effect of a programme or policy on specified outcomes, typically using a comparison group.

Imperfect AgencyTermImperfect Agent, Agency Imperfection

A situation in which an agent, such as a physician, does not perfectly represent the principal's interests due to differing incentives or information.

Implementation IntentionTermIf-Then Planning, Action Planning

A specific plan linking an anticipated situational cue to a predetermined goal-directed response, usually framed as an if-then statement.

Implementation ResearchTermImplementation Science, D and I Research

A field developing and testing methods to promote systematic uptake of evidence-based interventions into routine practice and policy.

Implementation StrategyTermImplementation Method, Adoption Strategy

A specific method used to promote successful adoption of an evidence-based practice, such as academic detailing or audit and feedback.

Implementation SupportTermAdoption Support, Implementation Assistance

Resources and guidance helping healthcare organisations adopt and apply an assessment body's published recommendations into actual clinical practice.

Implicit RationingTermCovert Rationing, Bedside Rationing

An approach applying access limits through mechanisms such as clinical discretion or waiting lists, without explicit, publicly disclosed criteria.

Implied ConsentTermInferred Consent, Tacit Consent

Consent inferred from a patient's actions or the circumstances of care, rather than an explicit statement, such as extending an arm for blood draw.

Importance SamplingConceptWeighted Sampling, Importance-Weighted Monte Carlo

A variance reduction technique for Monte Carlo simulation that deliberately oversamples important regions of a distribution, then reweights the samples to correct for this.

Impoverishing Expenditure MeasureTermImpoverishment Indicator, Poverty Impact Measure

A quantitative indicator assessing the extent to which out-of-pocket healthcare spending pushes households below, or further below, a poverty line.

Impoverishing Health ExpenditureConceptImpoverishing Out-of-Pocket Spending, Poverty-Inducing Health Cost

Out-of-pocket healthcare spending that pushes household income or consumption below an established poverty line, or further below it.

ImpoverishmentTermMedical Poverty, Poverty from Health Costs

A state where household income or consumption falls below an established poverty line, which out-of-pocket healthcare spending can cause or worsen.

ImprecisionTermEffect Estimate Uncertainty, Wide Confidence Interval

A GRADE evidence quality domain assessing whether a study's confidence intervals are narrow enough to support a confident conclusion about the true effect.

Improvement TrajectoryTermImprovement Path, Performance Trajectory

The pattern of change in an organisation's performance metrics over time, assessing whether quality improvement efforts produce sustained progress.

ImputationConceptMissing-Value Substitution, Value Filling

A technique replacing missing data values with estimated substitutes, ranging from simple mean substitution to sophisticated multiple imputation approaches.

In-NetworkTermNetwork Provider, Contracted Provider

A designation for providers with a contractual agreement to provide services at negotiated rates within a specific insurance plan.

In-SampleTermApparent Performance, Training-Data Performance

Describing performance calculated using the same data that built a statistical model, unlike out-of-sample performance assessed on independent data.

INAHTATermInternational Network of HTA Agencies, HTA Agency Network

The International Network of Agencies for Health Technology Assessment, connecting national and regional agencies worldwide for information sharing.

Incentive InterventionTermFinancial Incentive Programme, Reward Intervention

The use of monetary or non-monetary rewards to encourage a desired health behaviour, such as smoking cessation.

IncidenceConceptNew-Case Rate, New-Case Frequency

The number of new cases of a disease occurring within a defined population over a specified period, unlike prevalence, which counts existing cases.

Incidence RateTermIncidence Density, Person-Time Rate

A measure of disease frequency calculated as new cases divided by total person-time at risk observed, accounting for varying follow-up lengths.

Incidence Rate RatioConceptIRR, Incidence Density Ratio

A measure comparing the incidence rate of an outcome between two groups, accounting for differences in total person-time at risk.

Incident InvestigationTerm

A systematic inquiry determining the facts, causes, and appropriate response following a reported compliance concern or significant incident.

Incident ReportingTermIncident Report System, Safety Event Log

A formal system through which staff document instances of patient harm, near misses, or other safety concerns within their organisation.

Inclusion CriteriaTermTrial Inclusion Rules, Eligibility Characteristics

The specific characteristics an individual must have to be eligible for a trial, such as a confirmed diagnosis or age range.

Inclusion ErrorTermOver-Targeting, Leakage

The extension of a targeted programme's benefits to individuals who do not meet its intended eligibility criteria.

Income Elasticity of DemandConceptIncome Elasticity, Demand Income Responsiveness

A measure of how quantity demanded responds to a change in consumer income, calculated as percentage change in demand over percentage change in income.

Income StatementTerm

A financial statement summarising an organisation's revenues, expenses, and resulting profit or loss over a specified period.

Incomplete TreatmentTerm

A coping strategy in which a patient begins but does not complete a prescribed treatment course due to cost concerns.

InconsistencyTermDirect-Indirect Discrepancy, Evidence Discordance

Within network meta-analysis, a discrepancy between direct and indirect evidence for the same comparison, indicating the two sources disagree.

Incontinence EconomicsTerm

The application of health economic evaluation to urinary and faecal incontinence, covering behavioural therapy, medication, devices, and surgery.

Increment-Decrement TableTerm

A multi-state life table method modelling transitions between health states, including both improvement and decline, over successive time periods.