Clinically important difference in dry eye: change in IDEEL-symptom bother
Fairchild, Carol J.; Chalmers, Robin L.; Begley, Carolyn G.
Optometry & Vision Science
PURPOSE: The impact of dry eye on everyday living (IDEEL) is a valid, reliable questionnaire with 3 modules; symptom bother (SB), quality of life, and treatment satisfaction. This study tests the utility of the 20-item IDEEL-SB to discrimate self-assessed severity in dry eye subjects and to determine the clinically important difference (CID) in IDEEL-SB score that relates to a self-report of global change in dry eye condition after treatment. METHODS: After randomization to 1 of 3 marketed tear replacements, dry eye subjects completed the IDEEL-SB at baseline, 1 and 4 wk and global change questionnaire on status of general health and dry eye at 1 and 4 wk (5-point Likert scale; “much better” to “much worse”). The IDEEL-SB score was the unweighted mean score x 25. CID was initially estimated by receiver-operator curve analysis (ROC) and global change questionnaire. Various IDEEL-SB change criteria were tested to maximize % agreement, kappa score, and effect size. RESULTS: The 74 subjects were 54.0 +/- 17.2 years old and 52 (70.3%) were female. At baseline, 56.3% rarely/never used replacement tears. Subjects rated their dry eye severity as mild (41%), moderate (50%), or severe (9%). IDEEL-SB discriminated dry eye severity well; average baseline scores were mild: 40.0 (SD = 7.5), moderate: 50.6 (SD = 11.0) and severe 64.3 (SD = 8.0) (p = 0.001). After 4 wk of drops usage, IDEEL-SB dropped among “improved” subjects by -13.3 (SD = 10.9), “same” shifted by -4.7 (SD = 9.4), “worsened” changed by 1.4 (SD = 11.1). ROC results show that a 12-point change in IDEEL-SB is a clinically significant change in symptoms. CONCLUSIONS: 12-Point shift in the IDEEL-SB module is a CID based on ROC and the distribution across self-assessed severity groups compared with their global assessment of change in condition with treatment.