Validity of standard gamble estimated quality of life in acute venous thrombosis

Introduction

The standard gamble is considered the ‘gold standard’ technique for measuring quality of life. We recently used the standard gamble to estimate quality of life in acute venous thrombosis, and found unexpected variability in the responses. The current study aimed to explore the reasons for variability by comparing the standard gamble technique in patients with acute venous thrombosis to other quality of life measurement tools.

Materials and Methods

Thrombosis clinic patients treated for venous thrombosis were eligible to participate. Patients evaluated their current health state by performing a standard gamble interview, reporting on a visual analogue scale, completing the SF-36 and disease specific questionnaires (PEmb-Qol and VEINES-QOL/Sym). Validity was assessed by correlating the standard gamble utilities with the other methods. Test-retest reliability, responsiveness and acceptability were also assessed.

Results

Forty-four patients were interviewed, with 16 attending for a repeat interview. The median standard gamble utility was 0.97 (0.84-1.0), SF-6D 0.64 (0.59 - 0.80) and visual analogue score 70 (60 - 80). Participants with pulmonary embolism had lower standard gamble estimates than those with deep vein thrombosis. There was good discriminant validity in that the standard gamble estimates were not associated with risk taking behavior, negative outlook, sex or education. Test-retest reliability with the standard gamble was moderate and there was evidence of a ceiling effect.

Conclusions

Standard gamble utilities are higher than other methods of measuring quality of life in venous thrombosis. The choice of utility values adopted in studies will impact on future economic studies.