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.

ICECAP-AConceptICEpop Capability Measure for Adults, Investigating Choice Experiments Capability Measure for Adults

ICECAP-A is a self-report capability wellbeing measure for adults, with five attributes scored on UK index values, for economic evaluation beyond health.

ICECAP-OConceptICEpop CAPability measure for Older people, ICECAP index of capability for older people

ICECAP-O is a five-attribute capability wellbeing measure for people aged 65 and over, with UK index values for evaluating health and social care.

ICHOM Standard SetConceptRoutine Care Standard Set, Outcome Standard Set, Set of Patient-Centered Outcome Measures

An ICHOM Standard Set is an agreed set of outcomes and case-mix variables for one medical condition, used to compare providers on the value of care.

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.

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.

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.

Impact EvaluationTermCausal Impact Study, Effect Evaluation, Impact Analysis

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.

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, Rate Ratio, Relative Rate, Comparative Rate

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, Error Reporting, Error Documentation, Mistake Reporting

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.

Incremental Analysis MethodTermIncremental Approach, Marginal Comparison Method

An analytic approach comparing the additional cost and effect of one option relative to the next best alternative, rather than each option's total.

Incremental BudgetTermIncremental Budgeting, Roll-Forward Budget

A budget built by adjusting the previous period's budget slightly rather than starting each line item from zero.

Incremental CostConceptAdditional Cost, Marginal Cost Difference

Incremental cost is the difference in expected total cost between one healthcare option and its stated comparator, calculated using the same population, perspective, time horizon, currency, price year and costing methods.

Incremental Cost-Effectiveness Ratio (ICER)ConceptIncremental Cost per Unit

The incremental cost-effectiveness ratio (ICER) is a treatment's extra cost divided by its extra health gain versus a comparator, such as cost per QALY.

Incremental Cost-Utility RatioConceptICUR

The incremental cost-utility ratio (ICUR) is the ICER of a cost-utility analysis: extra cost over a comparator divided by extra QALYs gained.

Incremental EffectivenessConceptAdditional Effectiveness, Incremental Health Gain

Incremental effectiveness is the difference in health outcomes between an intervention and its comparator, calculated in a consistent outcome unit and comparison direction.