Quality-Adjusted Life Year (QALY)
A quality-adjusted life year (QALY) combines length and quality of life in one measure: a year in full health counts as one QALY and death counts as zero.
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Quality-Adjusted Time Without Symptoms
Quality-adjusted time without symptoms (Q-TWiST) sums cancer survival time with toxicity, free of symptoms and after relapse, each weighted for quality.
Ratio Scale
Ratio scale is a level of measurement with equal intervals and a true zero, such as cost or survival time, so a claim of twice the cost is meaningful.
Relapse Period (REL)
Relapse period (REL) is the Q-TWiST health state covering survival time after relapse or progression, weighted by its own utility.
Relapse-Free Survival
Relapse-free survival (RFS) is the time from randomisation, or another stated start such as surgery, to relapse of the disease or death from any cause.
ReQoL-UI
ReQoL-UI is a preference-based index scoring seven ReQoL items as utilities, so mental health studies can estimate QALYs for cost-utility analysis.
Response Level
Response level is one of the ordered answer categories of an instrument dimension or item, such as the five levels of each EQ-5D-5L dimension.
Responsiveness
Responsiveness is the ability of a health outcome measure, such as a PROM or utility instrument, to detect real change over time in the health it measures.
SF-6Dv2
SF-6Dv2 is the revised SF-6D, a six-dimension preference-based classification scored from SF-36v2 answers, whose value sets give utilities for QALYs.
Short Physical Performance Battery
Short Physical Performance Battery (SPPB) is a timed test of balance, gait speed and chair stands in older people, scored 0 to 12, used in trials.
Six-Minute Walk Test
Six-minute walk test (6MWT) is a performance outcome that records distance walked in six minutes, used as an endpoint in heart and lung trials and in HTA.
Standard Gamble
The standard gamble (SG) values a health state for QALYs as the chance of full health, against death, that makes a gamble as good as the state for sure.
Standardised Mortality Ratio
The standardised mortality ratio (SMR) is observed deaths divided by deaths expected at reference rates for a group's age mix, used to gauge excess deaths.
Standardised Response Mean
The standardised response mean (SRM) is a responsiveness index for health outcome measures, the mean change divided by the standard deviation of change.
Statistical Process Control
Statistical process control (SPC) is a set of statistical methods for monitoring health service data over time to tell routine variation from real change.
Stochastic Frontier Analysis
Stochastic frontier analysis (SFA) is a regression method that scores hospital or health system efficiency, separating inefficiency from random noise.
Sullivan Method
The Sullivan method estimates health expectancy, such as healthy life expectancy, by weighting life-table person-years by age-specific health prevalence.
Time Trade-Off
The time trade-off (TTO) values a health state for QALYs by asking how many years in full health a person rates equal to a longer life in that state.
Time Without Symptoms of Progression
Time without symptoms of progression (TWiST) is survival free of disease symptoms and counted treatment toxicity, the reference state in Q-TWiST.
Timed Up and Go Test
Timed Up and Go Test (TUG) is a performance outcome timing how long a person takes to rise, walk 3 metres, turn and sit, used for mobility and falls risk.