Purpose
The Brief Pain Inventory (BPI) is an established questionnaire on the severity and impact of pain and is used widely for systemic conditions. Our purpose was to evaluate the BPI as a measure of symptom severity for Dry Eye Disease (DED).
Methods
The BPI was modified by replacing the word “pain” with “ocular discomfort” to form the Brief Ocular Discomfort Inventory (BODI). Patients [N=269] with DED from 20 centers self-administered the BODI and provided a separate single 0-10 rating of their overall DED severity during 1-3 visits. Rasch analysis using a Grouped Rating-Scale model (2 subscales; 4 discomfort items, 7 interference items, all with 11 response categories each) was applied to provide characteristics of the questionnaire (reliability, category structure, fit to the model, differential item functioning [DIF], and dimensionality) and patients (severity and fit). Correlations between patients’ ratings and BODI scores, as well as their respective changes, were assessed with Spearman correlations (ρ).
Results
Discomfort subscale categories and their thresholds were individually well represented and ordered, respectively, but they were not for the interference subscale (fig 1). All items fit the model well and no DIF by visit or severity was detected. Principal component analysis neither confirmed nor refuted the subscales as separate dimensions, though person severity scores for the subscales were highly correlated (ρ=0.75). Mean person severity indicated that the BODI targets a higher level of severity than was present in the study group, but patients with greater severity were more likely to be mis-measured (p=0.002) (fig 2). Patient ratings and BODI scores were highly correlated (ρ=0.74) and changes in ratings and changes in scores were moderately correlated (ρ=0.56).
Conclusions
The BODI generally performed well in scoring DED discomfort and interference with activity, although fewer response categories may be warranted for the interference subscale. The higher severity of mis-measured persons indicates that the BODI may not perform well in more severely affected patients than were present in this study, and needs to be evaluated on more severe DED patients before acceptance as a measure of DED symptom severity.
Keywords: 486 cornea: tears/tear film/dry eye •
669 quality of life