The Influence of Recall and Timing of Assessment on the Estimation of Quality-Adjusted Life-Years When Health Fluctuates Recurrently

OBJECTIVES: When health fluctuates recurrently, estimating quality of life (QOL) is challenging, risking over-/underestimation due to measures' recall periods and timing. To inform how/when to capture QOL, we compared responses using different recall periods and assessment timings. METHODS: For one 3-week chemotherapy cycle, cancer patients were randomly assigned to complete EQ-5D-5L or SF-12v2 (daily with a daily recall, weekly with a weekly recall, and at 3 weeks with a 3-week recall); a third group completed SF-12v2 daily with a 3-week recall. EQ-5D-5L and SF-6D utilities (anchored at 1 full health and 0 dead) were generated and repeated measures analysis of variance, t tests, and effect sizes were calculated to compare recall. RESULTS: A total of 503 patients consented; all 21 daily questionnaires were completed by 84 (50%), 67 (40%), and 72 (43%) in the groups. Both measures captured fluctuations in QOL suggesting differences are due to recall effects. Mean daily scores were greater than scores for the past week on days 7, 14, and 21 (P < .0001). Utility was underestimated (by 0.0782, 0.0374, and 0.0437) for EQ-5D-5L and (0.0387, 0.0266, and 0.0304) for SF-6D, with the EQ-5D-5L comparison on day 7 reaching a minimally important difference. The "past 3 weeks" generated the lowest scores (P < .0001), with utility underestimated by 0.0746 (EQ-5D-5L) and 0.0310 (SF-6D), heavily skewed by the first treatment week. CONCLUSIONS: The current practice of using a single estimate at the beginning or end of a cycle with a daily (EQ-5D-5L) or longer (SF-12/SF-36) recall could bias cost-effectiveness estimates. QOL should be captured frequently with short recall when fluctuations are likely and less frequently with longer recall in stable periods.