Abstract

To evaluate the psychometric characteristics of the Daily Sleep Interference Scale (DSIS) in patients with painful diabetic peripheral neuropathy (DPN) or postherpetic neuralgia (PHN), a post hoc secondary analysis of data from eight randomized clinical trials (four DPN and four PHN) was performed. Data were pooled within patient populations when assessment weeks were the same. The DSIS was completed by 1,124 DPN and 1,034 PHN patients. Patient-reported outcomes, including a Daily Pain Diary, the Short-Form McGill Pain Questionnaire, SF-36 Health Survey, Profile of Mood States, MOS-Sleep Scale (MOS-SS), EQ-5D, and Patient Global Impression of Change, were used to validate the DSIS. Test-retest reliability was high for both samples (intraclass correlation coefficient>0.90). The DSIS showed good construct validity, with moderate to high correlations between the DSIS and weekly mean pain scores (r=0.48-0.80), MOS-SS sleep disturbance subscale (r=0.45-0.64), MPQ-SF Pain Experience (r=0.37-0.61), and VAS (r=0.42-0.72). The DSIS showed good discriminant validity in both groups; high and low MOS-SS sleep disturbance groups had significantly different DSIS scores (P<0.001). DPN patients who improved minimally on the Patient Global Impression of Change and in pain scores improved 1.5-2 DSIS points on average; for PHN, patient scores improved an average of 1-2 points. The DSIS demonstrated robust test-retest reliability, good construct and discriminant validity and responsiveness in painful DPN and PHN patients. A 1-2 point change on the DSIS might be interpreted as an important difference.