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Christopher Hwang, Jane Reeves Ellis, Sue Tolleson-Rinehart, Richard Davis; Determining the Minimal Clinically Important Difference of the UNC Dry Eye Management Scale. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):4492. doi: https://doi.org/.
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Many patient-reported outcomes (PRO) questionnaires have been developed to assess dry eye disease (DED), but few have established a minimal clinically important difference (MCID) in accordance with FDA guidelines. Therefore, to further develop the novel UNC Dry Eye Management Scale (DEMS), I established an initial estimation of the MCID of the instrument as well as assessed patient perceptions of symptom change versus score change via questionnaires in an observational clinical study.
I recruited 33 patients who had a prior DEMS score from a UNC ophthalmology cornea clinic in Chapel Hill, NC for study in the months of May and June 2014. I compared patients’ change in the DEMS scores from the most recent prior visit to patient-reported assessments of change in symptoms at the time of this study. Using anchor-based methods to determine the MCID, I obtained linear regression coefficients from the comparison to be my estimation of the MCID. I also recorded clinical assessments of the patients’ disease severity (tear break-up time, Schirmer test, Oxford grading scheme), and I administered another questionnaire to assess patient perceptions of score change as it relates to symptom change.
All 33 patients in this first attempt to establish MCID were included in analysis (33.3% male, 67.7% female, mean age 60.5 years). Anchors were correlated with DEMS score changes. The MCID ranged from ½ point using linear regression analysis (β = -0.54, CI = -0.97 to -0.12, R2 = 0.18, p = 0.014) to ~1 point (SD 1.32) using descriptive statistics. Patients felt that a change of approximately 2 points (SD = 0.95) was needed to represent an improvement/worsening of symptoms. The UNC DEMS had modest Spearman's Rank correlations with clinical tests (Schirmer test: -0.4045, p = 0.0266; Oxford grading scheme: +0.3713, p = 0.0364; Tear break-up time: -0.3559, p = 0.0456).
The UNC DEMS is a valid, responsive PRO instrument that can be used easily in the clinic to aid in the management of dry eye disease over time.
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