Stefano Garzon

Research · Oct 23, 2026

Health-related quality of life as an outcome

Concept

Health-related quality of life (HRQL) measures a participant’s life from the perspective of health and treatment. It belongs to the patient-reported outcomes, defined by the FDA as a report of health status that comes directly from the patient, without interpretation by a clinician.

Many interventions for chronic disease aim to relieve symptoms and preserve function. In these cases, survival and events do not answer the whole question. HRQL measures the effect of disease and treatment in terms that make sense to the participant.

Sugarbaker and colleagues studied 26 patients with soft tissue sarcoma randomized to amputation plus chemotherapy or limb-sparing surgery plus radiation and chemotherapy. The hypothesis of better quality of life with limb-sparing surgery was not confirmed. According to Friedman, the amputation group reported better mobility and sexual function.

Dimensions

HRQL measures are multidimensional. There is agreement on four main dimensions:

Additional dimensions include sleep, cognitive function, sexual function and work impact. The dimensions measured should match the trial’s aims. Measuring dimensions the intervention does not affect adds participant burden without gain. The protocol should justify the dimensions included and excluded.

Choice of instrument

Instruments are generic (SF-36, EQ-5D), disease-specific (FACT and EORTC QLQ in cancer) or symptom-specific (pain, anxiety). Reviews have proposed minimum attributes: a conceptual model, reliability, validity, responsiveness to change, interpretability of scores, cultural and language adaptation, feasibility in the setting, and burden for participants and staff.

Single items (a 0 to 10 rating) reduce burden. Multi-item questionnaires have higher content validity and reliability. The instrument’s standard scoring algorithm should be followed so that scores are interpretable and comparable across studies.

The CLASS trial randomized 798 patients with primary varicose veins to foam, laser or surgery. The primary outcomes were disease-specific HRQL (Aberdeen Varicose Veins Questionnaire) and generic HRQL (SF-36 and EQ-5D) at 6 months. Disease-specific HRQL was slightly worse after foam than after surgery (P = 0.006) and similar between laser and surgery.

Timing and mode of assessment

The baseline assessment should precede randomization. Follow-up assessments should coincide with the period in which change is expected from the intervention or the disease. Acute conditions with risk of relapse require longer follow-up.

The mode of collection (in person, telephone, mail, online) affects completeness, cost and bias. Interviews yield more complete data but are subject to interviewer bias. Self-administered questionnaires ease answers on sensitive topics. The same instruments must be used in all groups. Missing HRQL data are rarely random, because sicker participants respond less.

Minimal important difference

A statistically different score may lack clinical relevance. The minimal important difference is the smallest change perceived by the participant as improvement or worsening and that would lead a clinician to change management. It varies with population and context, and there is no consensus on the best method to estimate it.

Estrogen plus progestin in the WHI illustrates the point. In 16,608 women, treatment had no significant effect on general health, vitality, mental health, depressive symptoms or sexual satisfaction. There was a statistically significant but small benefit in sleep disturbance, physical function and bodily pain at 1 year, absent at 3 years. In the estrogen-alone arm, the reduction in sleep disturbance at 1 year was 0.4 points on a 20-point scale.

Utility measures

Psychometric measures describe dimensions. Utility measures assign each health state a value between 0 (death) and 1 (full health), obtained by standard gamble, time trade-off or multi-attribute scales. They allow morbidity and mortality to be combined into quality-adjusted life years (QALYs), used in cost-effectiveness analyses.

Common errors when reading a paper

What to check when reading a trial

  1. Rationale for the dimensions measured and their link to the trial’s aim.
  2. An instrument validated in the language and population of the study, with standard scoring.
  3. Baseline assessment before randomization and follow-up times compatible with the expected effect.
  4. Data completeness by group and the method for missing data.
  5. A prespecified minimal important difference and the size of the effect relative to it.
  6. Blinding of participants and assessors.

References