Determining the Minimal Clinically Important Difference of the UNC Dry Eye Management Scale

Abstract

Purpose: 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.

Methods: 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.

Results: 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).

Conclusions: 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.