OBJECTIVES: When health fluctuates recurrently, obtaining meaningful quality-of-life estimates is challenging. Quality-of-life changes may be missed or over/underestimated due to measures’ recall periods and timing. Using chemotherapy as a case study, we compare responses using different recall periods and timing to inform how/when to capture quality-of-life during predictable recurrent fluctuations in health; and consider the implications for other contexts with fluctuations.

METHODS: During one 3-weekly cycle of chemotherapy for cancer, patients were randomly assigned to complete:

(1) EQ-5D-5L daily with a daily recall period, weekly with a weekly timeframe, and at 3 weeks with a 3-week timeframe

(2) SF-12v2 daily with a daily recall period, weekly with a weekly timeframe, and at 3 weeks with a 3-week timeframe;

(3) SF-12v2 daily with a 3-week recall period;

Utilities (values anchored at 1 (full-health) and 0 (dead)) were generated and repeated measures ANOVA, t-tests and effect sizes calculated.

RESULTS: 503 patients consented; all 21 daily questionnaires were completed by 84(50%), 67(40%), 72(43%) in the groups respectively.

Both measures captured fluctuations in quality-of-life suggesting differences are due to recall effects. Mean daily scores were greater than scores for the past week at days 7, 14 and 21 (p<0.0001), which were greater than the past 3 weeks (p<0.0001).

By capturing quality-of-life with a ‘past week’ recall at days 7, 14 or 21, utility was overestimated by 0.0782 to 0.0266, with the comparison at day 7 reaching a minimally important difference.

Capturing quality-of-life with ‘past 3 weeks’ overestimated utility by 0.0746 and 0.0310 for EQ-5D and SF-6D, heavily skewed by the first treatment week.

CONCLUSIONS: Current practice of using a single estimate with a daily (EQ-5D) or longer (SF-12/SF-36) recall could bias cost-effectiveness estimates. Quality-of-life should be captured frequently with short recall when fluctuations are likely, with longer recall less frequently in more stable periods.