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C. J. Fairchild, R. Chalmers, C. Begley; Clinically Significant Differences in the Symptom Bother (SB) Module of the Impact of Dry Eye on Every Day Life (IDEEL) Questionnaire. Invest. Ophthalmol. Vis. Sci. 2007;48(13):6022.
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The IDEEL is a valid, reliable questionnaire with 3 modules; Symptom Bother (SB), Quality of Life, and Treatment Satisfaction. The SB module discriminates well between dry eye (DE) subjects (i.e., Sjogren’s vs. non-Sjogren’s KCS). This study was conducted to test the utility of the IDEEL-SB to distinguish self-assessed severity in KCS subjects and to determine the clinically important difference (CID) in SB that relates to a global improvement (GI) in condition with treatment.
KCS subjects completed the IDEEL SB at baseline, 1 and 4 weeks after starting a QID tear replacement regimen with 1 of 3 tear replacements. At weeks 1 and 4 they also completed GI questions on status of general health and dry eye condition on a 5-point Likert scale ("much better" to "much worse") with an appropriate recall period. The SB score was based on unweighted mean score x 25. CID was determined by anchor-based GI question and effect size method (ES) based on distribution. ES (mean change/SD of mean baseline) of 0.20-0.49 is small, 0.50-0.79 is moderate, and ≥ 0.80 is large.
The 74 subjects were 54.0 + 17.2 years old and 52 were female. Habitually, 56.3% of them rarely/never used tear replacement drops and 43.7% used drops more often. They rated their DE severity as mild (40%), moderate (50%) or severe (9%). Baseline SB score was 40.0 (SD=7.5) for mild, 50.6 (SD=11.0) for moderate, and 64.3 (SD=8.0) for severe subjects (p=0.001). After 4 weeks use of QID drops, change in SB for subjects who reported GI as "improved" averaged 13.3 + 10.9 while those who reported "same" had a shift of 4.7 + 9.4, those who "worsened" change -1.4 + 11.1. The pattern of change in SB with treatment for all severity and improvement groups indicates that a 12-point change in SB is a CID with an ES = 1.14.
A 12-point shift in the Symptom Bother module of the IDEEL appears to be a clinically important difference based on effect size and the distribution across severity groups compared to their global assessment of change in condition.
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