This material is the copyright of the original publisher. Unauthorised copying and distribution is prohibited. Estimating Preference-Based EQ-5D Health State Utilities or Item Responses from Neuropathic Pain Scores

Background: Preference-based health state utilities are required for many health economic evaluations. When the direct evidence of such is lacking and only condition-specific scores are available, establishing a ‘mapping’ relationship between instruments can be useful. Objective: Our objective was to map the 11-point Pain Intensity Numerical Rating Scale (PI-NRS-11), a pain-specific instrument ranging from 0 (‘no pain’) to 10 (‘pain as bad as you can imagine’), to the EQ-5D, a preferencebased generic instrument. Methods: We used web survey data collected from adult US respondents who (i) had ‡3 months of neuropathic pain (NP), either painful diabetic peripheral neuropathy (pDPN) or post-herpetic neuralgia (PHN); (ii) were receiving medications treating NP; and (iii) had completed the EQ-5D and PI-NRS-11. We explored indirect and direct mapping approaches. The indirect method took a probabilistic approach using ordered logistic models (OLMs) predicting response levels for each EQ-5D item via repeated Monte Carlo simulations before computing utilities. The direct approach simply predicted EQ-5D utilities directly using ordinary least squares (OLS). Categorical scores of PI-NRS-11 were used as the predictors. Patient age, gender, and pain duration were additionally controlled in the full model specification. Seventy percent of the data were used for estimation and 30% for prediction. Mean square errors (MSEs) and 95% confidence intervals (CIs) of prediction errors were reported. Results: A total of 2719 respondents were included. Mean (SD) age was 55.48 (10.65) years and 56.23% were female. Average NP duration was 61 months and 58% gave scores ‡6 on the PI-NRS-11. The clinical pain scores were significantly associated with all EQ-5D items, especially with the ‘pain/ discomfort’ item (p<0.001).The observedmean (SD) EQ-5D indexwas 0.594 (0.22). Predicted utilities and responses showed good representation of the